Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Fast Userspace Mutexes (which I call "Futexes!"). |
| 3 | * (C) Rusty Russell, IBM 2002 |
| 4 | * |
| 5 | * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar |
| 6 | * (C) Copyright 2003 Red Hat Inc, All Rights Reserved |
| 7 | * |
| 8 | * Removed page pinning, fix privately mapped COW pages and other cleanups |
| 9 | * (C) Copyright 2003, 2004 Jamie Lokier |
| 10 | * |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 11 | * Robust futex support started by Ingo Molnar |
| 12 | * (C) Copyright 2006 Red Hat Inc, All Rights Reserved |
| 13 | * Thanks to Thomas Gleixner for suggestions, analysis and fixes. |
| 14 | * |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 15 | * PI-futex support started by Ingo Molnar and Thomas Gleixner |
| 16 | * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| 17 | * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> |
| 18 | * |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 19 | * PRIVATE futexes by Eric Dumazet |
| 20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> |
| 21 | * |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 22 | * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com> |
| 23 | * Copyright (C) IBM Corporation, 2009 |
| 24 | * Thanks to Thomas Gleixner for conceptual design and careful reviews. |
| 25 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 26 | * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly |
| 27 | * enough at me, Linus for the original (flawed) idea, Matthew |
| 28 | * Kirkwood for proof-of-concept implementation. |
| 29 | * |
| 30 | * "The futexes are also cursed." |
| 31 | * "But they come in a choice of three flavours!" |
| 32 | * |
| 33 | * This program is free software; you can redistribute it and/or modify |
| 34 | * it under the terms of the GNU General Public License as published by |
| 35 | * the Free Software Foundation; either version 2 of the License, or |
| 36 | * (at your option) any later version. |
| 37 | * |
| 38 | * This program is distributed in the hope that it will be useful, |
| 39 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 40 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 41 | * GNU General Public License for more details. |
| 42 | * |
| 43 | * You should have received a copy of the GNU General Public License |
| 44 | * along with this program; if not, write to the Free Software |
| 45 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 46 | */ |
| 47 | #include <linux/slab.h> |
| 48 | #include <linux/poll.h> |
| 49 | #include <linux/fs.h> |
| 50 | #include <linux/file.h> |
| 51 | #include <linux/jhash.h> |
| 52 | #include <linux/init.h> |
| 53 | #include <linux/futex.h> |
| 54 | #include <linux/mount.h> |
| 55 | #include <linux/pagemap.h> |
| 56 | #include <linux/syscalls.h> |
Jesper Juhl | 7ed20e1 | 2005-05-01 08:59:14 -0700 | [diff] [blame] | 57 | #include <linux/signal.h> |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 58 | #include <linux/module.h> |
Andrey Mirkin | fd5eea4 | 2007-10-16 23:30:13 -0700 | [diff] [blame] | 59 | #include <linux/magic.h> |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 60 | #include <linux/pid.h> |
| 61 | #include <linux/nsproxy.h> |
| 62 | |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 63 | #include <asm/futex.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 64 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 65 | #include "rtmutex_common.h" |
| 66 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 67 | int __read_mostly futex_cmpxchg_enabled; |
| 68 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 69 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
| 70 | |
| 71 | /* |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 72 | * Priority Inheritance state: |
| 73 | */ |
| 74 | struct futex_pi_state { |
| 75 | /* |
| 76 | * list of 'owned' pi_state instances - these have to be |
| 77 | * cleaned up in do_exit() if the task exits prematurely: |
| 78 | */ |
| 79 | struct list_head list; |
| 80 | |
| 81 | /* |
| 82 | * The PI object: |
| 83 | */ |
| 84 | struct rt_mutex pi_mutex; |
| 85 | |
| 86 | struct task_struct *owner; |
| 87 | atomic_t refcount; |
| 88 | |
| 89 | union futex_key key; |
| 90 | }; |
| 91 | |
| 92 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 93 | * We use this hashed waitqueue instead of a normal wait_queue_t, so |
| 94 | * we can wake only the relevant ones (hashed queues may be shared). |
| 95 | * |
| 96 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 97 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 98 | * The order of wakup is always to make the first condition true, then |
Darren Hart | 73500ac | 2008-12-17 17:29:56 -0800 | [diff] [blame] | 99 | * wake up q->waiter, then make the second condition true. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 100 | */ |
| 101 | struct futex_q { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 102 | struct plist_node list; |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 103 | /* Waiter reference */ |
| 104 | struct task_struct *task; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 105 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 106 | /* Which hash list lock to use: */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 107 | spinlock_t *lock_ptr; |
| 108 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 109 | /* Key which the futex is hashed on: */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | union futex_key key; |
| 111 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 112 | /* Optional priority inheritance state: */ |
| 113 | struct futex_pi_state *pi_state; |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 114 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 115 | /* rt_waiter storage for requeue_pi: */ |
| 116 | struct rt_mutex_waiter *rt_waiter; |
| 117 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 118 | /* Bitset for the optional bitmasked wakeup */ |
| 119 | u32 bitset; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 120 | }; |
| 121 | |
| 122 | /* |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 123 | * Hash buckets are shared by all the futex_keys that hash to the same |
| 124 | * location. Each key may have multiple futex_q structures, one for each task |
| 125 | * waiting on a futex. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 126 | */ |
| 127 | struct futex_hash_bucket { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 128 | spinlock_t lock; |
| 129 | struct plist_head chain; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 130 | }; |
| 131 | |
| 132 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; |
| 133 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 134 | /* |
| 135 | * We hash on the keys returned from get_futex_key (see below). |
| 136 | */ |
| 137 | static struct futex_hash_bucket *hash_futex(union futex_key *key) |
| 138 | { |
| 139 | u32 hash = jhash2((u32*)&key->both.word, |
| 140 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, |
| 141 | key->both.offset); |
| 142 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; |
| 143 | } |
| 144 | |
| 145 | /* |
| 146 | * Return 1 if two futex_keys are equal, 0 otherwise. |
| 147 | */ |
| 148 | static inline int match_futex(union futex_key *key1, union futex_key *key2) |
| 149 | { |
| 150 | return (key1->both.word == key2->both.word |
| 151 | && key1->both.ptr == key2->both.ptr |
| 152 | && key1->both.offset == key2->both.offset); |
| 153 | } |
| 154 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 155 | /* |
| 156 | * Take a reference to the resource addressed by a key. |
| 157 | * Can be called while holding spinlocks. |
| 158 | * |
| 159 | */ |
| 160 | static void get_futex_key_refs(union futex_key *key) |
| 161 | { |
| 162 | if (!key->both.ptr) |
| 163 | return; |
| 164 | |
| 165 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { |
| 166 | case FUT_OFF_INODE: |
| 167 | atomic_inc(&key->shared.inode->i_count); |
| 168 | break; |
| 169 | case FUT_OFF_MMSHARED: |
| 170 | atomic_inc(&key->private.mm->mm_count); |
| 171 | break; |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | /* |
| 176 | * Drop a reference to the resource addressed by a key. |
| 177 | * The hash bucket spinlock must not be held. |
| 178 | */ |
| 179 | static void drop_futex_key_refs(union futex_key *key) |
| 180 | { |
Darren Hart | 90621c4 | 2008-12-29 19:43:21 -0800 | [diff] [blame] | 181 | if (!key->both.ptr) { |
| 182 | /* If we're here then we tried to put a key we failed to get */ |
| 183 | WARN_ON_ONCE(1); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 184 | return; |
Darren Hart | 90621c4 | 2008-12-29 19:43:21 -0800 | [diff] [blame] | 185 | } |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 186 | |
| 187 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { |
| 188 | case FUT_OFF_INODE: |
| 189 | iput(key->shared.inode); |
| 190 | break; |
| 191 | case FUT_OFF_MMSHARED: |
| 192 | mmdrop(key->private.mm); |
| 193 | break; |
| 194 | } |
| 195 | } |
| 196 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 197 | /** |
| 198 | * get_futex_key - Get parameters which are the keys for a futex. |
| 199 | * @uaddr: virtual address of the futex |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 200 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 201 | * @key: address where result is stored. |
| 202 | * |
| 203 | * Returns a negative error code or 0 |
| 204 | * The key words are stored in *key on success. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 205 | * |
Josef "Jeff" Sipek | f3a43f3 | 2006-12-08 02:36:43 -0800 | [diff] [blame] | 206 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 207 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
| 208 | * We can usually work out the index without swapping in the page. |
| 209 | * |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 210 | * lock_page() might sleep, the caller should not hold a spinlock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 211 | */ |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 212 | static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 213 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 214 | unsigned long address = (unsigned long)uaddr; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 215 | struct mm_struct *mm = current->mm; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 216 | struct page *page; |
| 217 | int err; |
| 218 | |
| 219 | /* |
| 220 | * The futex address must be "naturally" aligned. |
| 221 | */ |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 222 | key->both.offset = address % PAGE_SIZE; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 223 | if (unlikely((address % sizeof(u32)) != 0)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 224 | return -EINVAL; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 225 | address -= key->both.offset; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 226 | |
| 227 | /* |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 228 | * PROCESS_PRIVATE futexes are fast. |
| 229 | * As the mm cannot disappear under us and the 'key' only needs |
| 230 | * virtual address, we dont even have to find the underlying vma. |
| 231 | * Note : We do have to check 'uaddr' is a valid user address, |
| 232 | * but access_ok() should be faster than find_vma() |
| 233 | */ |
| 234 | if (!fshared) { |
| 235 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) |
| 236 | return -EFAULT; |
| 237 | key->private.mm = mm; |
| 238 | key->private.address = address; |
Peter Zijlstra | 42569c3 | 2008-09-30 12:33:07 +0200 | [diff] [blame] | 239 | get_futex_key_refs(key); |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 240 | return 0; |
| 241 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 242 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 243 | again: |
Peter Zijlstra | 734b05b | 2008-09-26 19:32:22 +0200 | [diff] [blame] | 244 | err = get_user_pages_fast(address, 1, 0, &page); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 245 | if (err < 0) |
| 246 | return err; |
| 247 | |
| 248 | lock_page(page); |
| 249 | if (!page->mapping) { |
| 250 | unlock_page(page); |
| 251 | put_page(page); |
| 252 | goto again; |
| 253 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 254 | |
| 255 | /* |
| 256 | * Private mappings are handled in a simple way. |
| 257 | * |
| 258 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if |
| 259 | * it's a read-only handle, it's expected that futexes attach to |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 260 | * the object not the particular process. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 261 | */ |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 262 | if (PageAnon(page)) { |
| 263 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 264 | key->private.mm = mm; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 265 | key->private.address = address; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 266 | } else { |
| 267 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ |
| 268 | key->shared.inode = page->mapping->host; |
| 269 | key->shared.pgoff = page->index; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 270 | } |
| 271 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 272 | get_futex_key_refs(key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 273 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 274 | unlock_page(page); |
| 275 | put_page(page); |
| 276 | return 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 277 | } |
| 278 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 279 | static inline |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 280 | void put_futex_key(int fshared, union futex_key *key) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 281 | { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 282 | drop_futex_key_refs(key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 283 | } |
| 284 | |
Darren Hart | 4b1c486 | 2009-04-03 13:39:42 -0700 | [diff] [blame] | 285 | /** |
| 286 | * futex_top_waiter() - Return the highest priority waiter on a futex |
| 287 | * @hb: the hash bucket the futex_q's reside in |
| 288 | * @key: the futex key (to distinguish it from other futex futex_q's) |
| 289 | * |
| 290 | * Must be called with the hb lock held. |
| 291 | */ |
| 292 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, |
| 293 | union futex_key *key) |
| 294 | { |
| 295 | struct futex_q *this; |
| 296 | |
| 297 | plist_for_each_entry(this, &hb->chain, list) { |
| 298 | if (match_futex(&this->key, key)) |
| 299 | return this; |
| 300 | } |
| 301 | return NULL; |
| 302 | } |
| 303 | |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 304 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
| 305 | { |
| 306 | u32 curval; |
| 307 | |
| 308 | pagefault_disable(); |
| 309 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); |
| 310 | pagefault_enable(); |
| 311 | |
| 312 | return curval; |
| 313 | } |
| 314 | |
| 315 | static int get_futex_value_locked(u32 *dest, u32 __user *from) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 316 | { |
| 317 | int ret; |
| 318 | |
Peter Zijlstra | a866374 | 2006-12-06 20:32:20 -0800 | [diff] [blame] | 319 | pagefault_disable(); |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 320 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
Peter Zijlstra | a866374 | 2006-12-06 20:32:20 -0800 | [diff] [blame] | 321 | pagefault_enable(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 322 | |
| 323 | return ret ? -EFAULT : 0; |
| 324 | } |
| 325 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 326 | |
| 327 | /* |
| 328 | * PI code: |
| 329 | */ |
| 330 | static int refill_pi_state_cache(void) |
| 331 | { |
| 332 | struct futex_pi_state *pi_state; |
| 333 | |
| 334 | if (likely(current->pi_state_cache)) |
| 335 | return 0; |
| 336 | |
Burman Yan | 4668edc | 2006-12-06 20:38:51 -0800 | [diff] [blame] | 337 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 338 | |
| 339 | if (!pi_state) |
| 340 | return -ENOMEM; |
| 341 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 342 | INIT_LIST_HEAD(&pi_state->list); |
| 343 | /* pi_mutex gets initialized later */ |
| 344 | pi_state->owner = NULL; |
| 345 | atomic_set(&pi_state->refcount, 1); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 346 | pi_state->key = FUTEX_KEY_INIT; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 347 | |
| 348 | current->pi_state_cache = pi_state; |
| 349 | |
| 350 | return 0; |
| 351 | } |
| 352 | |
| 353 | static struct futex_pi_state * alloc_pi_state(void) |
| 354 | { |
| 355 | struct futex_pi_state *pi_state = current->pi_state_cache; |
| 356 | |
| 357 | WARN_ON(!pi_state); |
| 358 | current->pi_state_cache = NULL; |
| 359 | |
| 360 | return pi_state; |
| 361 | } |
| 362 | |
| 363 | static void free_pi_state(struct futex_pi_state *pi_state) |
| 364 | { |
| 365 | if (!atomic_dec_and_test(&pi_state->refcount)) |
| 366 | return; |
| 367 | |
| 368 | /* |
| 369 | * If pi_state->owner is NULL, the owner is most probably dying |
| 370 | * and has cleaned up the pi_state already |
| 371 | */ |
| 372 | if (pi_state->owner) { |
| 373 | spin_lock_irq(&pi_state->owner->pi_lock); |
| 374 | list_del_init(&pi_state->list); |
| 375 | spin_unlock_irq(&pi_state->owner->pi_lock); |
| 376 | |
| 377 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); |
| 378 | } |
| 379 | |
| 380 | if (current->pi_state_cache) |
| 381 | kfree(pi_state); |
| 382 | else { |
| 383 | /* |
| 384 | * pi_state->list is already empty. |
| 385 | * clear pi_state->owner. |
| 386 | * refcount is at 0 - put it back to 1. |
| 387 | */ |
| 388 | pi_state->owner = NULL; |
| 389 | atomic_set(&pi_state->refcount, 1); |
| 390 | current->pi_state_cache = pi_state; |
| 391 | } |
| 392 | } |
| 393 | |
| 394 | /* |
| 395 | * Look up the task based on what TID userspace gave us. |
| 396 | * We dont trust it. |
| 397 | */ |
| 398 | static struct task_struct * futex_find_get_task(pid_t pid) |
| 399 | { |
| 400 | struct task_struct *p; |
David Howells | c69e8d9 | 2008-11-14 10:39:19 +1100 | [diff] [blame] | 401 | const struct cred *cred = current_cred(), *pcred; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 402 | |
Oleg Nesterov | d359b54 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 403 | rcu_read_lock(); |
Pavel Emelyanov | 228ebcb | 2007-10-18 23:40:16 -0700 | [diff] [blame] | 404 | p = find_task_by_vpid(pid); |
David Howells | c69e8d9 | 2008-11-14 10:39:19 +1100 | [diff] [blame] | 405 | if (!p) { |
Thomas Gleixner | a06381f | 2007-06-23 11:48:40 +0200 | [diff] [blame] | 406 | p = ERR_PTR(-ESRCH); |
David Howells | c69e8d9 | 2008-11-14 10:39:19 +1100 | [diff] [blame] | 407 | } else { |
| 408 | pcred = __task_cred(p); |
| 409 | if (cred->euid != pcred->euid && |
| 410 | cred->euid != pcred->uid) |
| 411 | p = ERR_PTR(-ESRCH); |
| 412 | else |
| 413 | get_task_struct(p); |
| 414 | } |
Thomas Gleixner | a06381f | 2007-06-23 11:48:40 +0200 | [diff] [blame] | 415 | |
Oleg Nesterov | d359b54 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 416 | rcu_read_unlock(); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 417 | |
| 418 | return p; |
| 419 | } |
| 420 | |
| 421 | /* |
| 422 | * This task is holding PI mutexes at exit time => bad. |
| 423 | * Kernel cleans up PI-state, but userspace is likely hosed. |
| 424 | * (Robust-futex cleanup is separate and might save the day for userspace.) |
| 425 | */ |
| 426 | void exit_pi_state_list(struct task_struct *curr) |
| 427 | { |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 428 | struct list_head *next, *head = &curr->pi_state_list; |
| 429 | struct futex_pi_state *pi_state; |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 430 | struct futex_hash_bucket *hb; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 431 | union futex_key key = FUTEX_KEY_INIT; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 432 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 433 | if (!futex_cmpxchg_enabled) |
| 434 | return; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 435 | /* |
| 436 | * We are a ZOMBIE and nobody can enqueue itself on |
| 437 | * pi_state_list anymore, but we have to be careful |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 438 | * versus waiters unqueueing themselves: |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 439 | */ |
| 440 | spin_lock_irq(&curr->pi_lock); |
| 441 | while (!list_empty(head)) { |
| 442 | |
| 443 | next = head->next; |
| 444 | pi_state = list_entry(next, struct futex_pi_state, list); |
| 445 | key = pi_state->key; |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 446 | hb = hash_futex(&key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 447 | spin_unlock_irq(&curr->pi_lock); |
| 448 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 449 | spin_lock(&hb->lock); |
| 450 | |
| 451 | spin_lock_irq(&curr->pi_lock); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 452 | /* |
| 453 | * We dropped the pi-lock, so re-check whether this |
| 454 | * task still owns the PI-state: |
| 455 | */ |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 456 | if (head->next != next) { |
| 457 | spin_unlock(&hb->lock); |
| 458 | continue; |
| 459 | } |
| 460 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 461 | WARN_ON(pi_state->owner != curr); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 462 | WARN_ON(list_empty(&pi_state->list)); |
| 463 | list_del_init(&pi_state->list); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 464 | pi_state->owner = NULL; |
| 465 | spin_unlock_irq(&curr->pi_lock); |
| 466 | |
| 467 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 468 | |
| 469 | spin_unlock(&hb->lock); |
| 470 | |
| 471 | spin_lock_irq(&curr->pi_lock); |
| 472 | } |
| 473 | spin_unlock_irq(&curr->pi_lock); |
| 474 | } |
| 475 | |
| 476 | static int |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 477 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
| 478 | union futex_key *key, struct futex_pi_state **ps) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 479 | { |
| 480 | struct futex_pi_state *pi_state = NULL; |
| 481 | struct futex_q *this, *next; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 482 | struct plist_head *head; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 483 | struct task_struct *p; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 484 | pid_t pid = uval & FUTEX_TID_MASK; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 485 | |
| 486 | head = &hb->chain; |
| 487 | |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 488 | plist_for_each_entry_safe(this, next, head, list) { |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 489 | if (match_futex(&this->key, key)) { |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 490 | /* |
| 491 | * Another waiter already exists - bump up |
| 492 | * the refcount and return its pi_state: |
| 493 | */ |
| 494 | pi_state = this->pi_state; |
Thomas Gleixner | 06a9ec2 | 2006-07-10 04:44:30 -0700 | [diff] [blame] | 495 | /* |
| 496 | * Userspace might have messed up non PI and PI futexes |
| 497 | */ |
| 498 | if (unlikely(!pi_state)) |
| 499 | return -EINVAL; |
| 500 | |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 501 | WARN_ON(!atomic_read(&pi_state->refcount)); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 502 | WARN_ON(pid && pi_state->owner && |
| 503 | pi_state->owner->pid != pid); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 504 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 505 | atomic_inc(&pi_state->refcount); |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 506 | *ps = pi_state; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 507 | |
| 508 | return 0; |
| 509 | } |
| 510 | } |
| 511 | |
| 512 | /* |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 513 | * We are the first waiter - try to look up the real owner and attach |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 514 | * the new pi_state to it, but bail out when TID = 0 |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 515 | */ |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 516 | if (!pid) |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 517 | return -ESRCH; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 518 | p = futex_find_get_task(pid); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 519 | if (IS_ERR(p)) |
| 520 | return PTR_ERR(p); |
| 521 | |
| 522 | /* |
| 523 | * We need to look at the task state flags to figure out, |
| 524 | * whether the task is exiting. To protect against the do_exit |
| 525 | * change of the task flags, we do this protected by |
| 526 | * p->pi_lock: |
| 527 | */ |
| 528 | spin_lock_irq(&p->pi_lock); |
| 529 | if (unlikely(p->flags & PF_EXITING)) { |
| 530 | /* |
| 531 | * The task is on the way out. When PF_EXITPIDONE is |
| 532 | * set, we know that the task has finished the |
| 533 | * cleanup: |
| 534 | */ |
| 535 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; |
| 536 | |
| 537 | spin_unlock_irq(&p->pi_lock); |
| 538 | put_task_struct(p); |
| 539 | return ret; |
| 540 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 541 | |
| 542 | pi_state = alloc_pi_state(); |
| 543 | |
| 544 | /* |
| 545 | * Initialize the pi_mutex in locked state and make 'p' |
| 546 | * the owner of it: |
| 547 | */ |
| 548 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); |
| 549 | |
| 550 | /* Store the key for possible exit cleanups: */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 551 | pi_state->key = *key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 552 | |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 553 | WARN_ON(!list_empty(&pi_state->list)); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 554 | list_add(&pi_state->list, &p->pi_state_list); |
| 555 | pi_state->owner = p; |
| 556 | spin_unlock_irq(&p->pi_lock); |
| 557 | |
| 558 | put_task_struct(p); |
| 559 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 560 | *ps = pi_state; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 561 | |
| 562 | return 0; |
| 563 | } |
| 564 | |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 565 | /** |
| 566 | * futex_lock_pi_atomic() - atomic work required to acquire a pi aware futex |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 567 | * @uaddr: the pi futex user address |
| 568 | * @hb: the pi futex hash bucket |
| 569 | * @key: the futex key associated with uaddr and hb |
| 570 | * @ps: the pi_state pointer where we store the result of the |
| 571 | * lookup |
| 572 | * @task: the task to perform the atomic lock work for. This will |
| 573 | * be "current" except in the case of requeue pi. |
| 574 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 575 | * |
| 576 | * Returns: |
| 577 | * 0 - ready to wait |
| 578 | * 1 - acquired the lock |
| 579 | * <0 - error |
| 580 | * |
| 581 | * The hb->lock and futex_key refs shall be held by the caller. |
| 582 | */ |
| 583 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, |
| 584 | union futex_key *key, |
| 585 | struct futex_pi_state **ps, |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 586 | struct task_struct *task, int set_waiters) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 587 | { |
| 588 | int lock_taken, ret, ownerdied = 0; |
| 589 | u32 uval, newval, curval; |
| 590 | |
| 591 | retry: |
| 592 | ret = lock_taken = 0; |
| 593 | |
| 594 | /* |
| 595 | * To avoid races, we attempt to take the lock here again |
| 596 | * (by doing a 0 -> TID atomic cmpxchg), while holding all |
| 597 | * the locks. It will most likely not succeed. |
| 598 | */ |
| 599 | newval = task_pid_vnr(task); |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 600 | if (set_waiters) |
| 601 | newval |= FUTEX_WAITERS; |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 602 | |
| 603 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); |
| 604 | |
| 605 | if (unlikely(curval == -EFAULT)) |
| 606 | return -EFAULT; |
| 607 | |
| 608 | /* |
| 609 | * Detect deadlocks. |
| 610 | */ |
| 611 | if ((unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(task)))) |
| 612 | return -EDEADLK; |
| 613 | |
| 614 | /* |
| 615 | * Surprise - we got the lock. Just return to userspace: |
| 616 | */ |
| 617 | if (unlikely(!curval)) |
| 618 | return 1; |
| 619 | |
| 620 | uval = curval; |
| 621 | |
| 622 | /* |
| 623 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone |
| 624 | * to wake at the next unlock. |
| 625 | */ |
| 626 | newval = curval | FUTEX_WAITERS; |
| 627 | |
| 628 | /* |
| 629 | * There are two cases, where a futex might have no owner (the |
| 630 | * owner TID is 0): OWNER_DIED. We take over the futex in this |
| 631 | * case. We also do an unconditional take over, when the owner |
| 632 | * of the futex died. |
| 633 | * |
| 634 | * This is safe as we are protected by the hash bucket lock ! |
| 635 | */ |
| 636 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { |
| 637 | /* Keep the OWNER_DIED bit */ |
| 638 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(task); |
| 639 | ownerdied = 0; |
| 640 | lock_taken = 1; |
| 641 | } |
| 642 | |
| 643 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
| 644 | |
| 645 | if (unlikely(curval == -EFAULT)) |
| 646 | return -EFAULT; |
| 647 | if (unlikely(curval != uval)) |
| 648 | goto retry; |
| 649 | |
| 650 | /* |
| 651 | * We took the lock due to owner died take over. |
| 652 | */ |
| 653 | if (unlikely(lock_taken)) |
| 654 | return 1; |
| 655 | |
| 656 | /* |
| 657 | * We dont have the lock. Look up the PI state (or create it if |
| 658 | * we are the first waiter): |
| 659 | */ |
| 660 | ret = lookup_pi_state(uval, hb, key, ps); |
| 661 | |
| 662 | if (unlikely(ret)) { |
| 663 | switch (ret) { |
| 664 | case -ESRCH: |
| 665 | /* |
| 666 | * No owner found for this futex. Check if the |
| 667 | * OWNER_DIED bit is set to figure out whether |
| 668 | * this is a robust futex or not. |
| 669 | */ |
| 670 | if (get_futex_value_locked(&curval, uaddr)) |
| 671 | return -EFAULT; |
| 672 | |
| 673 | /* |
| 674 | * We simply start over in case of a robust |
| 675 | * futex. The code above will take the futex |
| 676 | * and return happy. |
| 677 | */ |
| 678 | if (curval & FUTEX_OWNER_DIED) { |
| 679 | ownerdied = 1; |
| 680 | goto retry; |
| 681 | } |
| 682 | default: |
| 683 | break; |
| 684 | } |
| 685 | } |
| 686 | |
| 687 | return ret; |
| 688 | } |
| 689 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 690 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 691 | * The hash bucket lock must be held when this is called. |
| 692 | * Afterwards, the futex_q must not be accessed. |
| 693 | */ |
| 694 | static void wake_futex(struct futex_q *q) |
| 695 | { |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 696 | struct task_struct *p = q->task; |
| 697 | |
| 698 | /* |
| 699 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
| 700 | * a non futex wake up happens on another CPU then the task |
| 701 | * might exit and p would dereference a non existing task |
| 702 | * struct. Prevent this by holding a reference on p across the |
| 703 | * wake up. |
| 704 | */ |
| 705 | get_task_struct(p); |
| 706 | |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 707 | plist_del(&q->list, &q->list.plist); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 708 | /* |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 709 | * The waiting task can free the futex_q as soon as |
| 710 | * q->lock_ptr = NULL is written, without taking any locks. A |
| 711 | * memory barrier is required here to prevent the following |
| 712 | * store to lock_ptr from getting ahead of the plist_del. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 713 | */ |
Ralf Baechle | ccdea2f | 2006-12-06 20:40:26 -0800 | [diff] [blame] | 714 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 715 | q->lock_ptr = NULL; |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 716 | |
| 717 | wake_up_state(p, TASK_NORMAL); |
| 718 | put_task_struct(p); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 719 | } |
| 720 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 721 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
| 722 | { |
| 723 | struct task_struct *new_owner; |
| 724 | struct futex_pi_state *pi_state = this->pi_state; |
| 725 | u32 curval, newval; |
| 726 | |
| 727 | if (!pi_state) |
| 728 | return -EINVAL; |
| 729 | |
Ingo Molnar | 21778867 | 2007-03-16 13:38:31 -0800 | [diff] [blame] | 730 | spin_lock(&pi_state->pi_mutex.wait_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 731 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
| 732 | |
| 733 | /* |
| 734 | * This happens when we have stolen the lock and the original |
| 735 | * pending owner did not enqueue itself back on the rt_mutex. |
| 736 | * Thats not a tragedy. We know that way, that a lock waiter |
| 737 | * is on the fly. We make the futex_q waiter the pending owner. |
| 738 | */ |
| 739 | if (!new_owner) |
| 740 | new_owner = this->task; |
| 741 | |
| 742 | /* |
| 743 | * We pass it to the next owner. (The WAITERS bit is always |
| 744 | * kept enabled while there is PI state around. We must also |
| 745 | * preserve the owner died bit.) |
| 746 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 747 | if (!(uval & FUTEX_OWNER_DIED)) { |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 748 | int ret = 0; |
| 749 | |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 750 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 751 | |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 752 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 753 | |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 754 | if (curval == -EFAULT) |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 755 | ret = -EFAULT; |
Thomas Gleixner | cde898f | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 756 | else if (curval != uval) |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 757 | ret = -EINVAL; |
| 758 | if (ret) { |
| 759 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
| 760 | return ret; |
| 761 | } |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 762 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 763 | |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 764 | spin_lock_irq(&pi_state->owner->pi_lock); |
| 765 | WARN_ON(list_empty(&pi_state->list)); |
| 766 | list_del_init(&pi_state->list); |
| 767 | spin_unlock_irq(&pi_state->owner->pi_lock); |
| 768 | |
| 769 | spin_lock_irq(&new_owner->pi_lock); |
| 770 | WARN_ON(!list_empty(&pi_state->list)); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 771 | list_add(&pi_state->list, &new_owner->pi_state_list); |
| 772 | pi_state->owner = new_owner; |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 773 | spin_unlock_irq(&new_owner->pi_lock); |
| 774 | |
Ingo Molnar | 21778867 | 2007-03-16 13:38:31 -0800 | [diff] [blame] | 775 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 776 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 777 | |
| 778 | return 0; |
| 779 | } |
| 780 | |
| 781 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) |
| 782 | { |
| 783 | u32 oldval; |
| 784 | |
| 785 | /* |
| 786 | * There is no waiter, so we unlock the futex. The owner died |
| 787 | * bit has not to be preserved here. We are the owner: |
| 788 | */ |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 789 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 790 | |
| 791 | if (oldval == -EFAULT) |
| 792 | return oldval; |
| 793 | if (oldval != uval) |
| 794 | return -EAGAIN; |
| 795 | |
| 796 | return 0; |
| 797 | } |
| 798 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 799 | /* |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 800 | * Express the locking dependencies for lockdep: |
| 801 | */ |
| 802 | static inline void |
| 803 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 804 | { |
| 805 | if (hb1 <= hb2) { |
| 806 | spin_lock(&hb1->lock); |
| 807 | if (hb1 < hb2) |
| 808 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); |
| 809 | } else { /* hb1 > hb2 */ |
| 810 | spin_lock(&hb2->lock); |
| 811 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); |
| 812 | } |
| 813 | } |
| 814 | |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 815 | static inline void |
| 816 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 817 | { |
Darren Hart | f061d35 | 2009-03-12 15:11:18 -0700 | [diff] [blame] | 818 | spin_unlock(&hb1->lock); |
Ingo Molnar | 88f502f | 2009-03-13 10:32:07 +0100 | [diff] [blame] | 819 | if (hb1 != hb2) |
| 820 | spin_unlock(&hb2->lock); |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 821 | } |
| 822 | |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 823 | /* |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 824 | * Wake up waiters matching bitset queued on this futex (uaddr). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 825 | */ |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 826 | static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 827 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 828 | struct futex_hash_bucket *hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 829 | struct futex_q *this, *next; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 830 | struct plist_head *head; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 831 | union futex_key key = FUTEX_KEY_INIT; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 832 | int ret; |
| 833 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 834 | if (!bitset) |
| 835 | return -EINVAL; |
| 836 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 837 | ret = get_futex_key(uaddr, fshared, &key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 838 | if (unlikely(ret != 0)) |
| 839 | goto out; |
| 840 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 841 | hb = hash_futex(&key); |
| 842 | spin_lock(&hb->lock); |
| 843 | head = &hb->chain; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 844 | |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 845 | plist_for_each_entry_safe(this, next, head, list) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 846 | if (match_futex (&this->key, &key)) { |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 847 | if (this->pi_state || this->rt_waiter) { |
Ingo Molnar | ed6f7b1 | 2006-07-01 04:35:46 -0700 | [diff] [blame] | 848 | ret = -EINVAL; |
| 849 | break; |
| 850 | } |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 851 | |
| 852 | /* Check if one of the bits is set in both bitsets */ |
| 853 | if (!(this->bitset & bitset)) |
| 854 | continue; |
| 855 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 856 | wake_futex(this); |
| 857 | if (++ret >= nr_wake) |
| 858 | break; |
| 859 | } |
| 860 | } |
| 861 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 862 | spin_unlock(&hb->lock); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 863 | put_futex_key(fshared, &key); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 864 | out: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 865 | return ret; |
| 866 | } |
| 867 | |
| 868 | /* |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 869 | * Wake up all waiters hashed on the physical page that is mapped |
| 870 | * to this virtual address: |
| 871 | */ |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 872 | static int |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 873 | futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 874 | int nr_wake, int nr_wake2, int op) |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 875 | { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 876 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 877 | struct futex_hash_bucket *hb1, *hb2; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 878 | struct plist_head *head; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 879 | struct futex_q *this, *next; |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 880 | int ret, op_ret; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 881 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 882 | retry: |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 883 | ret = get_futex_key(uaddr1, fshared, &key1); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 884 | if (unlikely(ret != 0)) |
| 885 | goto out; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 886 | ret = get_futex_key(uaddr2, fshared, &key2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 887 | if (unlikely(ret != 0)) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 888 | goto out_put_key1; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 889 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 890 | hb1 = hash_futex(&key1); |
| 891 | hb2 = hash_futex(&key2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 892 | |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 893 | double_lock_hb(hb1, hb2); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 894 | retry_private: |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 895 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 896 | if (unlikely(op_ret < 0)) { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 897 | u32 dummy; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 898 | |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 899 | double_unlock_hb(hb1, hb2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 900 | |
David Howells | 7ee1dd3 | 2006-01-06 00:11:44 -0800 | [diff] [blame] | 901 | #ifndef CONFIG_MMU |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 902 | /* |
| 903 | * we don't get EFAULT from MMU faults if we don't have an MMU, |
| 904 | * but we might get them from range checking |
| 905 | */ |
David Howells | 7ee1dd3 | 2006-01-06 00:11:44 -0800 | [diff] [blame] | 906 | ret = op_ret; |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 907 | goto out_put_keys; |
David Howells | 7ee1dd3 | 2006-01-06 00:11:44 -0800 | [diff] [blame] | 908 | #endif |
| 909 | |
David Gibson | 796f8d9 | 2005-11-07 00:59:33 -0800 | [diff] [blame] | 910 | if (unlikely(op_ret != -EFAULT)) { |
| 911 | ret = op_ret; |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 912 | goto out_put_keys; |
David Gibson | 796f8d9 | 2005-11-07 00:59:33 -0800 | [diff] [blame] | 913 | } |
| 914 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 915 | ret = get_user(dummy, uaddr2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 916 | if (ret) |
Darren Hart | de87fcc | 2009-03-12 00:55:46 -0700 | [diff] [blame] | 917 | goto out_put_keys; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 918 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 919 | if (!fshared) |
| 920 | goto retry_private; |
| 921 | |
Darren Hart | de87fcc | 2009-03-12 00:55:46 -0700 | [diff] [blame] | 922 | put_futex_key(fshared, &key2); |
| 923 | put_futex_key(fshared, &key1); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 924 | goto retry; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 925 | } |
| 926 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 927 | head = &hb1->chain; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 928 | |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 929 | plist_for_each_entry_safe(this, next, head, list) { |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 930 | if (match_futex (&this->key, &key1)) { |
| 931 | wake_futex(this); |
| 932 | if (++ret >= nr_wake) |
| 933 | break; |
| 934 | } |
| 935 | } |
| 936 | |
| 937 | if (op_ret > 0) { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 938 | head = &hb2->chain; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 939 | |
| 940 | op_ret = 0; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 941 | plist_for_each_entry_safe(this, next, head, list) { |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 942 | if (match_futex (&this->key, &key2)) { |
| 943 | wake_futex(this); |
| 944 | if (++op_ret >= nr_wake2) |
| 945 | break; |
| 946 | } |
| 947 | } |
| 948 | ret += op_ret; |
| 949 | } |
| 950 | |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 951 | double_unlock_hb(hb1, hb2); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 952 | out_put_keys: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 953 | put_futex_key(fshared, &key2); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 954 | out_put_key1: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 955 | put_futex_key(fshared, &key1); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 956 | out: |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 957 | return ret; |
| 958 | } |
| 959 | |
Darren Hart | 9121e47 | 2009-04-03 13:40:31 -0700 | [diff] [blame] | 960 | /** |
| 961 | * requeue_futex() - Requeue a futex_q from one hb to another |
| 962 | * @q: the futex_q to requeue |
| 963 | * @hb1: the source hash_bucket |
| 964 | * @hb2: the target hash_bucket |
| 965 | * @key2: the new key for the requeued futex_q |
| 966 | */ |
| 967 | static inline |
| 968 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, |
| 969 | struct futex_hash_bucket *hb2, union futex_key *key2) |
| 970 | { |
| 971 | |
| 972 | /* |
| 973 | * If key1 and key2 hash to the same bucket, no need to |
| 974 | * requeue. |
| 975 | */ |
| 976 | if (likely(&hb1->chain != &hb2->chain)) { |
| 977 | plist_del(&q->list, &hb1->chain); |
| 978 | plist_add(&q->list, &hb2->chain); |
| 979 | q->lock_ptr = &hb2->lock; |
| 980 | #ifdef CONFIG_DEBUG_PI_LIST |
| 981 | q->list.plist.lock = &hb2->lock; |
| 982 | #endif |
| 983 | } |
| 984 | get_futex_key_refs(key2); |
| 985 | q->key = *key2; |
| 986 | } |
| 987 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 988 | /** |
| 989 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue |
| 990 | * q: the futex_q |
| 991 | * key: the key of the requeue target futex |
| 992 | * |
| 993 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the |
| 994 | * target futex if it is uncontended or via a lock steal. Set the futex_q key |
| 995 | * to the requeue target futex so the waiter can detect the wakeup on the right |
| 996 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect |
| 997 | * atomic lock acquisition. Must be called with the q->lock_ptr held. |
| 998 | */ |
| 999 | static inline |
| 1000 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key) |
| 1001 | { |
| 1002 | drop_futex_key_refs(&q->key); |
| 1003 | get_futex_key_refs(key); |
| 1004 | q->key = *key; |
| 1005 | |
| 1006 | WARN_ON(plist_node_empty(&q->list)); |
| 1007 | plist_del(&q->list, &q->list.plist); |
| 1008 | |
| 1009 | WARN_ON(!q->rt_waiter); |
| 1010 | q->rt_waiter = NULL; |
| 1011 | |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 1012 | wake_up_state(q->task, TASK_NORMAL); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1013 | } |
| 1014 | |
| 1015 | /** |
| 1016 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1017 | * @pifutex: the user address of the to futex |
| 1018 | * @hb1: the from futex hash bucket, must be locked by the caller |
| 1019 | * @hb2: the to futex hash bucket, must be locked by the caller |
| 1020 | * @key1: the from futex key |
| 1021 | * @key2: the to futex key |
| 1022 | * @ps: address to store the pi_state pointer |
| 1023 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1024 | * |
| 1025 | * Try and get the lock on behalf of the top waiter if we can do it atomically. |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1026 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
| 1027 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. |
| 1028 | * hb1 and hb2 must be held by the caller. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1029 | * |
| 1030 | * Returns: |
| 1031 | * 0 - failed to acquire the lock atomicly |
| 1032 | * 1 - acquired the lock |
| 1033 | * <0 - error |
| 1034 | */ |
| 1035 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, |
| 1036 | struct futex_hash_bucket *hb1, |
| 1037 | struct futex_hash_bucket *hb2, |
| 1038 | union futex_key *key1, union futex_key *key2, |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1039 | struct futex_pi_state **ps, int set_waiters) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1040 | { |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1041 | struct futex_q *top_waiter = NULL; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1042 | u32 curval; |
| 1043 | int ret; |
| 1044 | |
| 1045 | if (get_futex_value_locked(&curval, pifutex)) |
| 1046 | return -EFAULT; |
| 1047 | |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1048 | /* |
| 1049 | * Find the top_waiter and determine if there are additional waiters. |
| 1050 | * If the caller intends to requeue more than 1 waiter to pifutex, |
| 1051 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, |
| 1052 | * as we have means to handle the possible fault. If not, don't set |
| 1053 | * the bit unecessarily as it will force the subsequent unlock to enter |
| 1054 | * the kernel. |
| 1055 | */ |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1056 | top_waiter = futex_top_waiter(hb1, key1); |
| 1057 | |
| 1058 | /* There are no waiters, nothing for us to do. */ |
| 1059 | if (!top_waiter) |
| 1060 | return 0; |
| 1061 | |
| 1062 | /* |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1063 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
| 1064 | * the contended case or if set_waiters is 1. The pi_state is returned |
| 1065 | * in ps in contended cases. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1066 | */ |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1067 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
| 1068 | set_waiters); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1069 | if (ret == 1) |
| 1070 | requeue_pi_wake_futex(top_waiter, key2); |
| 1071 | |
| 1072 | return ret; |
| 1073 | } |
| 1074 | |
| 1075 | /** |
| 1076 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 |
| 1077 | * uaddr1: source futex user address |
| 1078 | * uaddr2: target futex user address |
| 1079 | * nr_wake: number of waiters to wake (must be 1 for requeue_pi) |
| 1080 | * nr_requeue: number of waiters to requeue (0-INT_MAX) |
| 1081 | * requeue_pi: if we are attempting to requeue from a non-pi futex to a |
| 1082 | * pi futex (pi to pi requeue is not supported) |
| 1083 | * |
| 1084 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire |
| 1085 | * uaddr2 atomically on behalf of the top waiter. |
| 1086 | * |
| 1087 | * Returns: |
| 1088 | * >=0 - on success, the number of tasks requeued or woken |
| 1089 | * <0 - on error |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1090 | */ |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1091 | static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1092 | int nr_wake, int nr_requeue, u32 *cmpval, |
| 1093 | int requeue_pi) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1094 | { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1095 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1096 | int drop_count = 0, task_count = 0, ret; |
| 1097 | struct futex_pi_state *pi_state = NULL; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1098 | struct futex_hash_bucket *hb1, *hb2; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1099 | struct plist_head *head1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1100 | struct futex_q *this, *next; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1101 | u32 curval2; |
| 1102 | |
| 1103 | if (requeue_pi) { |
| 1104 | /* |
| 1105 | * requeue_pi requires a pi_state, try to allocate it now |
| 1106 | * without any locks in case it fails. |
| 1107 | */ |
| 1108 | if (refill_pi_state_cache()) |
| 1109 | return -ENOMEM; |
| 1110 | /* |
| 1111 | * requeue_pi must wake as many tasks as it can, up to nr_wake |
| 1112 | * + nr_requeue, since it acquires the rt_mutex prior to |
| 1113 | * returning to userspace, so as to not leave the rt_mutex with |
| 1114 | * waiters and no owner. However, second and third wake-ups |
| 1115 | * cannot be predicted as they involve race conditions with the |
| 1116 | * first wake and a fault while looking up the pi_state. Both |
| 1117 | * pthread_cond_signal() and pthread_cond_broadcast() should |
| 1118 | * use nr_wake=1. |
| 1119 | */ |
| 1120 | if (nr_wake != 1) |
| 1121 | return -EINVAL; |
| 1122 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1123 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1124 | retry: |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1125 | if (pi_state != NULL) { |
| 1126 | /* |
| 1127 | * We will have to lookup the pi_state again, so free this one |
| 1128 | * to keep the accounting correct. |
| 1129 | */ |
| 1130 | free_pi_state(pi_state); |
| 1131 | pi_state = NULL; |
| 1132 | } |
| 1133 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1134 | ret = get_futex_key(uaddr1, fshared, &key1); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1135 | if (unlikely(ret != 0)) |
| 1136 | goto out; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1137 | ret = get_futex_key(uaddr2, fshared, &key2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1138 | if (unlikely(ret != 0)) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1139 | goto out_put_key1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1140 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1141 | hb1 = hash_futex(&key1); |
| 1142 | hb2 = hash_futex(&key2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1143 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1144 | retry_private: |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 1145 | double_lock_hb(hb1, hb2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1146 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1147 | if (likely(cmpval != NULL)) { |
| 1148 | u32 curval; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1149 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1150 | ret = get_futex_value_locked(&curval, uaddr1); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1151 | |
| 1152 | if (unlikely(ret)) { |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1153 | double_unlock_hb(hb1, hb2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1154 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1155 | ret = get_user(curval, uaddr1); |
| 1156 | if (ret) |
| 1157 | goto out_put_keys; |
| 1158 | |
| 1159 | if (!fshared) |
| 1160 | goto retry_private; |
| 1161 | |
Darren Hart | de87fcc | 2009-03-12 00:55:46 -0700 | [diff] [blame] | 1162 | put_futex_key(fshared, &key2); |
| 1163 | put_futex_key(fshared, &key1); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1164 | goto retry; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1165 | } |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1166 | if (curval != *cmpval) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1167 | ret = -EAGAIN; |
| 1168 | goto out_unlock; |
| 1169 | } |
| 1170 | } |
| 1171 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1172 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1173 | /* |
| 1174 | * Attempt to acquire uaddr2 and wake the top waiter. If we |
| 1175 | * intend to requeue waiters, force setting the FUTEX_WAITERS |
| 1176 | * bit. We force this here where we are able to easily handle |
| 1177 | * faults rather in the requeue loop below. |
| 1178 | */ |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1179 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1180 | &key2, &pi_state, nr_requeue); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1181 | |
| 1182 | /* |
| 1183 | * At this point the top_waiter has either taken uaddr2 or is |
| 1184 | * waiting on it. If the former, then the pi_state will not |
| 1185 | * exist yet, look it up one more time to ensure we have a |
| 1186 | * reference to it. |
| 1187 | */ |
| 1188 | if (ret == 1) { |
| 1189 | WARN_ON(pi_state); |
| 1190 | task_count++; |
| 1191 | ret = get_futex_value_locked(&curval2, uaddr2); |
| 1192 | if (!ret) |
| 1193 | ret = lookup_pi_state(curval2, hb2, &key2, |
| 1194 | &pi_state); |
| 1195 | } |
| 1196 | |
| 1197 | switch (ret) { |
| 1198 | case 0: |
| 1199 | break; |
| 1200 | case -EFAULT: |
| 1201 | double_unlock_hb(hb1, hb2); |
| 1202 | put_futex_key(fshared, &key2); |
| 1203 | put_futex_key(fshared, &key1); |
| 1204 | ret = get_user(curval2, uaddr2); |
| 1205 | if (!ret) |
| 1206 | goto retry; |
| 1207 | goto out; |
| 1208 | case -EAGAIN: |
| 1209 | /* The owner was exiting, try again. */ |
| 1210 | double_unlock_hb(hb1, hb2); |
| 1211 | put_futex_key(fshared, &key2); |
| 1212 | put_futex_key(fshared, &key1); |
| 1213 | cond_resched(); |
| 1214 | goto retry; |
| 1215 | default: |
| 1216 | goto out_unlock; |
| 1217 | } |
| 1218 | } |
| 1219 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1220 | head1 = &hb1->chain; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1221 | plist_for_each_entry_safe(this, next, head1, list) { |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1222 | if (task_count - nr_wake >= nr_requeue) |
| 1223 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1224 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1225 | if (!match_futex(&this->key, &key1)) |
| 1226 | continue; |
| 1227 | |
| 1228 | WARN_ON(!requeue_pi && this->rt_waiter); |
| 1229 | WARN_ON(requeue_pi && !this->rt_waiter); |
| 1230 | |
| 1231 | /* |
| 1232 | * Wake nr_wake waiters. For requeue_pi, if we acquired the |
| 1233 | * lock, we already woke the top_waiter. If not, it will be |
| 1234 | * woken by futex_unlock_pi(). |
| 1235 | */ |
| 1236 | if (++task_count <= nr_wake && !requeue_pi) { |
| 1237 | wake_futex(this); |
| 1238 | continue; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1239 | } |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1240 | |
| 1241 | /* |
| 1242 | * Requeue nr_requeue waiters and possibly one more in the case |
| 1243 | * of requeue_pi if we couldn't acquire the lock atomically. |
| 1244 | */ |
| 1245 | if (requeue_pi) { |
| 1246 | /* Prepare the waiter to take the rt_mutex. */ |
| 1247 | atomic_inc(&pi_state->refcount); |
| 1248 | this->pi_state = pi_state; |
| 1249 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, |
| 1250 | this->rt_waiter, |
| 1251 | this->task, 1); |
| 1252 | if (ret == 1) { |
| 1253 | /* We got the lock. */ |
| 1254 | requeue_pi_wake_futex(this, &key2); |
| 1255 | continue; |
| 1256 | } else if (ret) { |
| 1257 | /* -EDEADLK */ |
| 1258 | this->pi_state = NULL; |
| 1259 | free_pi_state(pi_state); |
| 1260 | goto out_unlock; |
| 1261 | } |
| 1262 | } |
| 1263 | requeue_futex(this, hb1, hb2, &key2); |
| 1264 | drop_count++; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1265 | } |
| 1266 | |
| 1267 | out_unlock: |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1268 | double_unlock_hb(hb1, hb2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1269 | |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1270 | /* drop_futex_key_refs() must be called outside the spinlocks. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1271 | while (--drop_count >= 0) |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1272 | drop_futex_key_refs(&key1); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1273 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1274 | out_put_keys: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1275 | put_futex_key(fshared, &key2); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1276 | out_put_key1: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1277 | put_futex_key(fshared, &key1); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1278 | out: |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1279 | if (pi_state != NULL) |
| 1280 | free_pi_state(pi_state); |
| 1281 | return ret ? ret : task_count; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1282 | } |
| 1283 | |
| 1284 | /* The key must be already stored in q->key. */ |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 1285 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1286 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1287 | struct futex_hash_bucket *hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1288 | |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1289 | get_futex_key_refs(&q->key); |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1290 | hb = hash_futex(&q->key); |
| 1291 | q->lock_ptr = &hb->lock; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1292 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1293 | spin_lock(&hb->lock); |
| 1294 | return hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1295 | } |
| 1296 | |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 1297 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1298 | { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1299 | int prio; |
| 1300 | |
| 1301 | /* |
| 1302 | * The priority used to register this element is |
| 1303 | * - either the real thread-priority for the real-time threads |
| 1304 | * (i.e. threads with a priority lower than MAX_RT_PRIO) |
| 1305 | * - or MAX_RT_PRIO for non-RT threads. |
| 1306 | * Thus, all RT-threads are woken first in priority order, and |
| 1307 | * the others are woken last, in FIFO order. |
| 1308 | */ |
| 1309 | prio = min(current->normal_prio, MAX_RT_PRIO); |
| 1310 | |
| 1311 | plist_node_init(&q->list, prio); |
| 1312 | #ifdef CONFIG_DEBUG_PI_LIST |
| 1313 | q->list.plist.lock = &hb->lock; |
| 1314 | #endif |
| 1315 | plist_add(&q->list, &hb->chain); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1316 | q->task = current; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1317 | spin_unlock(&hb->lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1318 | } |
| 1319 | |
| 1320 | static inline void |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1321 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1322 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1323 | spin_unlock(&hb->lock); |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1324 | drop_futex_key_refs(&q->key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1325 | } |
| 1326 | |
| 1327 | /* |
| 1328 | * queue_me and unqueue_me must be called as a pair, each |
| 1329 | * exactly once. They are called with the hashed spinlock held. |
| 1330 | */ |
| 1331 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1332 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
| 1333 | static int unqueue_me(struct futex_q *q) |
| 1334 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1335 | spinlock_t *lock_ptr; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1336 | int ret = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1337 | |
| 1338 | /* In the common case we don't take the spinlock, which is nice. */ |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1339 | retry: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1340 | lock_ptr = q->lock_ptr; |
Christian Borntraeger | e91467e | 2006-08-05 12:13:52 -0700 | [diff] [blame] | 1341 | barrier(); |
Stephen Hemminger | c80544d | 2007-10-18 03:07:05 -0700 | [diff] [blame] | 1342 | if (lock_ptr != NULL) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1343 | spin_lock(lock_ptr); |
| 1344 | /* |
| 1345 | * q->lock_ptr can change between reading it and |
| 1346 | * spin_lock(), causing us to take the wrong lock. This |
| 1347 | * corrects the race condition. |
| 1348 | * |
| 1349 | * Reasoning goes like this: if we have the wrong lock, |
| 1350 | * q->lock_ptr must have changed (maybe several times) |
| 1351 | * between reading it and the spin_lock(). It can |
| 1352 | * change again after the spin_lock() but only if it was |
| 1353 | * already changed before the spin_lock(). It cannot, |
| 1354 | * however, change back to the original value. Therefore |
| 1355 | * we can detect whether we acquired the correct lock. |
| 1356 | */ |
| 1357 | if (unlikely(lock_ptr != q->lock_ptr)) { |
| 1358 | spin_unlock(lock_ptr); |
| 1359 | goto retry; |
| 1360 | } |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1361 | WARN_ON(plist_node_empty(&q->list)); |
| 1362 | plist_del(&q->list, &q->list.plist); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1363 | |
| 1364 | BUG_ON(q->pi_state); |
| 1365 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1366 | spin_unlock(lock_ptr); |
| 1367 | ret = 1; |
| 1368 | } |
| 1369 | |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1370 | drop_futex_key_refs(&q->key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1371 | return ret; |
| 1372 | } |
| 1373 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1374 | /* |
| 1375 | * PI futexes can not be requeued and must remove themself from the |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1376 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
| 1377 | * and dropped here. |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1378 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1379 | static void unqueue_me_pi(struct futex_q *q) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1380 | { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1381 | WARN_ON(plist_node_empty(&q->list)); |
| 1382 | plist_del(&q->list, &q->list.plist); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1383 | |
| 1384 | BUG_ON(!q->pi_state); |
| 1385 | free_pi_state(q->pi_state); |
| 1386 | q->pi_state = NULL; |
| 1387 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1388 | spin_unlock(q->lock_ptr); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1389 | |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1390 | drop_futex_key_refs(&q->key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1391 | } |
| 1392 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1393 | /* |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1394 | * Fixup the pi_state owner with the new owner. |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1395 | * |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1396 | * Must be called with hash bucket lock held and mm->sem held for non |
| 1397 | * private futexes. |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1398 | */ |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1399 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1400 | struct task_struct *newowner, int fshared) |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1401 | { |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1402 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1403 | struct futex_pi_state *pi_state = q->pi_state; |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1404 | struct task_struct *oldowner = pi_state->owner; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1405 | u32 uval, curval, newval; |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1406 | int ret; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1407 | |
| 1408 | /* Owner died? */ |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1409 | if (!pi_state->owner) |
| 1410 | newtid |= FUTEX_OWNER_DIED; |
| 1411 | |
| 1412 | /* |
| 1413 | * We are here either because we stole the rtmutex from the |
| 1414 | * pending owner or we are the pending owner which failed to |
| 1415 | * get the rtmutex. We have to replace the pending owner TID |
| 1416 | * in the user space variable. This must be atomic as we have |
| 1417 | * to preserve the owner died bit here. |
| 1418 | * |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 1419 | * Note: We write the user space value _before_ changing the pi_state |
| 1420 | * because we can fault here. Imagine swapped out pages or a fork |
| 1421 | * that marked all the anonymous memory readonly for cow. |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1422 | * |
| 1423 | * Modifying pi_state _before_ the user space value would |
| 1424 | * leave the pi_state in an inconsistent state when we fault |
| 1425 | * here, because we need to drop the hash bucket lock to |
| 1426 | * handle the fault. This might be observed in the PID check |
| 1427 | * in lookup_pi_state. |
| 1428 | */ |
| 1429 | retry: |
| 1430 | if (get_futex_value_locked(&uval, uaddr)) |
| 1431 | goto handle_fault; |
| 1432 | |
| 1433 | while (1) { |
| 1434 | newval = (uval & FUTEX_OWNER_DIED) | newtid; |
| 1435 | |
| 1436 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
| 1437 | |
| 1438 | if (curval == -EFAULT) |
| 1439 | goto handle_fault; |
| 1440 | if (curval == uval) |
| 1441 | break; |
| 1442 | uval = curval; |
| 1443 | } |
| 1444 | |
| 1445 | /* |
| 1446 | * We fixed up user space. Now we need to fix the pi_state |
| 1447 | * itself. |
| 1448 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1449 | if (pi_state->owner != NULL) { |
| 1450 | spin_lock_irq(&pi_state->owner->pi_lock); |
| 1451 | WARN_ON(list_empty(&pi_state->list)); |
| 1452 | list_del_init(&pi_state->list); |
| 1453 | spin_unlock_irq(&pi_state->owner->pi_lock); |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1454 | } |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1455 | |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1456 | pi_state->owner = newowner; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1457 | |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1458 | spin_lock_irq(&newowner->pi_lock); |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1459 | WARN_ON(!list_empty(&pi_state->list)); |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1460 | list_add(&pi_state->list, &newowner->pi_state_list); |
| 1461 | spin_unlock_irq(&newowner->pi_lock); |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1462 | return 0; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1463 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1464 | /* |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1465 | * To handle the page fault we need to drop the hash bucket |
| 1466 | * lock here. That gives the other task (either the pending |
| 1467 | * owner itself or the task which stole the rtmutex) the |
| 1468 | * chance to try the fixup of the pi_state. So once we are |
| 1469 | * back from handling the fault we need to check the pi_state |
| 1470 | * after reacquiring the hash bucket lock and before trying to |
| 1471 | * do another fixup. When the fixup has been done already we |
| 1472 | * simply return. |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1473 | */ |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1474 | handle_fault: |
| 1475 | spin_unlock(q->lock_ptr); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1476 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1477 | ret = get_user(uval, uaddr); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1478 | |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1479 | spin_lock(q->lock_ptr); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1480 | |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1481 | /* |
| 1482 | * Check if someone else fixed it for us: |
| 1483 | */ |
| 1484 | if (pi_state->owner != oldowner) |
| 1485 | return 0; |
| 1486 | |
| 1487 | if (ret) |
| 1488 | return ret; |
| 1489 | |
| 1490 | goto retry; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1491 | } |
| 1492 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1493 | /* |
| 1494 | * In case we must use restart_block to restart a futex_wait, |
Steven Rostedt | ce6bd42 | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 1495 | * we encode in the 'flags' shared capability |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1496 | */ |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 1497 | #define FLAGS_SHARED 0x01 |
| 1498 | #define FLAGS_CLOCKRT 0x02 |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 1499 | #define FLAGS_HAS_TIMEOUT 0x04 |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1500 | |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1501 | static long futex_wait_restart(struct restart_block *restart); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1502 | static long futex_lock_pi_restart(struct restart_block *restart); |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 1503 | |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1504 | /** |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1505 | * fixup_owner() - Post lock pi_state and corner case management |
| 1506 | * @uaddr: user address of the futex |
| 1507 | * @fshared: whether the futex is shared (1) or not (0) |
| 1508 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
| 1509 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) |
| 1510 | * |
| 1511 | * After attempting to lock an rt_mutex, this function is called to cleanup |
| 1512 | * the pi_state owner as well as handle race conditions that may allow us to |
| 1513 | * acquire the lock. Must be called with the hb lock held. |
| 1514 | * |
| 1515 | * Returns: |
| 1516 | * 1 - success, lock taken |
| 1517 | * 0 - success, lock not taken |
| 1518 | * <0 - on error (-EFAULT) |
| 1519 | */ |
| 1520 | static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q, |
| 1521 | int locked) |
| 1522 | { |
| 1523 | struct task_struct *owner; |
| 1524 | int ret = 0; |
| 1525 | |
| 1526 | if (locked) { |
| 1527 | /* |
| 1528 | * Got the lock. We might not be the anticipated owner if we |
| 1529 | * did a lock-steal - fix up the PI-state in that case: |
| 1530 | */ |
| 1531 | if (q->pi_state->owner != current) |
| 1532 | ret = fixup_pi_state_owner(uaddr, q, current, fshared); |
| 1533 | goto out; |
| 1534 | } |
| 1535 | |
| 1536 | /* |
| 1537 | * Catch the rare case, where the lock was released when we were on the |
| 1538 | * way back before we locked the hash bucket. |
| 1539 | */ |
| 1540 | if (q->pi_state->owner == current) { |
| 1541 | /* |
| 1542 | * Try to get the rt_mutex now. This might fail as some other |
| 1543 | * task acquired the rt_mutex after we removed ourself from the |
| 1544 | * rt_mutex waiters list. |
| 1545 | */ |
| 1546 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { |
| 1547 | locked = 1; |
| 1548 | goto out; |
| 1549 | } |
| 1550 | |
| 1551 | /* |
| 1552 | * pi_state is incorrect, some other task did a lock steal and |
| 1553 | * we returned due to timeout or signal without taking the |
| 1554 | * rt_mutex. Too late. We can access the rt_mutex_owner without |
| 1555 | * locking, as the other task is now blocked on the hash bucket |
| 1556 | * lock. Fix the state up. |
| 1557 | */ |
| 1558 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); |
| 1559 | ret = fixup_pi_state_owner(uaddr, q, owner, fshared); |
| 1560 | goto out; |
| 1561 | } |
| 1562 | |
| 1563 | /* |
| 1564 | * Paranoia check. If we did not take the lock, then we should not be |
| 1565 | * the owner, nor the pending owner, of the rt_mutex. |
| 1566 | */ |
| 1567 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) |
| 1568 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " |
| 1569 | "pi-state %p\n", ret, |
| 1570 | q->pi_state->pi_mutex.owner, |
| 1571 | q->pi_state->owner); |
| 1572 | |
| 1573 | out: |
| 1574 | return ret ? ret : locked; |
| 1575 | } |
| 1576 | |
| 1577 | /** |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1578 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal |
| 1579 | * @hb: the futex hash bucket, must be locked by the caller |
| 1580 | * @q: the futex_q to queue up on |
| 1581 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1582 | */ |
| 1583 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 1584 | struct hrtimer_sleeper *timeout) |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1585 | { |
| 1586 | queue_me(q, hb); |
| 1587 | |
| 1588 | /* |
| 1589 | * There might have been scheduling since the queue_me(), as we |
| 1590 | * cannot hold a spinlock across the get_user() in case it |
| 1591 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 1592 | * queueing ourselves into the futex hash. This code thus has to |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1593 | * rely on the futex_wake() code removing us from hash when it |
| 1594 | * wakes us up. |
| 1595 | */ |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 1596 | set_current_state(TASK_INTERRUPTIBLE); |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1597 | |
| 1598 | /* Arm the timer */ |
| 1599 | if (timeout) { |
| 1600 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
| 1601 | if (!hrtimer_active(&timeout->timer)) |
| 1602 | timeout->task = NULL; |
| 1603 | } |
| 1604 | |
| 1605 | /* |
| 1606 | * !plist_node_empty() is safe here without any lock. |
| 1607 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
| 1608 | */ |
| 1609 | if (likely(!plist_node_empty(&q->list))) { |
| 1610 | /* |
| 1611 | * If the timer has already expired, current will already be |
| 1612 | * flagged for rescheduling. Only call schedule if there |
| 1613 | * is no timeout, or if it has yet to expire. |
| 1614 | */ |
| 1615 | if (!timeout || timeout->task) |
| 1616 | schedule(); |
| 1617 | } |
| 1618 | __set_current_state(TASK_RUNNING); |
| 1619 | } |
| 1620 | |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1621 | /** |
| 1622 | * futex_wait_setup() - Prepare to wait on a futex |
| 1623 | * @uaddr: the futex userspace address |
| 1624 | * @val: the expected value |
| 1625 | * @fshared: whether the futex is shared (1) or not (0) |
| 1626 | * @q: the associated futex_q |
| 1627 | * @hb: storage for hash_bucket pointer to be returned to caller |
| 1628 | * |
| 1629 | * Setup the futex_q and locate the hash_bucket. Get the futex value and |
| 1630 | * compare it with the expected value. Handle atomic faults internally. |
| 1631 | * Return with the hb lock held and a q.key reference on success, and unlocked |
| 1632 | * with no q.key reference on failure. |
| 1633 | * |
| 1634 | * Returns: |
| 1635 | * 0 - uaddr contains val and hb has been locked |
| 1636 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked |
| 1637 | */ |
| 1638 | static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared, |
| 1639 | struct futex_q *q, struct futex_hash_bucket **hb) |
| 1640 | { |
| 1641 | u32 uval; |
| 1642 | int ret; |
| 1643 | |
| 1644 | /* |
| 1645 | * Access the page AFTER the hash-bucket is locked. |
| 1646 | * Order is important: |
| 1647 | * |
| 1648 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); |
| 1649 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } |
| 1650 | * |
| 1651 | * The basic logical guarantee of a futex is that it blocks ONLY |
| 1652 | * if cond(var) is known to be true at the time of blocking, for |
| 1653 | * any cond. If we queued after testing *uaddr, that would open |
| 1654 | * a race condition where we could block indefinitely with |
| 1655 | * cond(var) false, which would violate the guarantee. |
| 1656 | * |
| 1657 | * A consequence is that futex_wait() can return zero and absorb |
| 1658 | * a wakeup when *uaddr != val on entry to the syscall. This is |
| 1659 | * rare, but normal. |
| 1660 | */ |
| 1661 | retry: |
| 1662 | q->key = FUTEX_KEY_INIT; |
| 1663 | ret = get_futex_key(uaddr, fshared, &q->key); |
| 1664 | if (unlikely(ret != 0)) |
Darren Hart | a5a2a0c | 2009-04-10 09:50:05 -0700 | [diff] [blame] | 1665 | return ret; |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1666 | |
| 1667 | retry_private: |
| 1668 | *hb = queue_lock(q); |
| 1669 | |
| 1670 | ret = get_futex_value_locked(&uval, uaddr); |
| 1671 | |
| 1672 | if (ret) { |
| 1673 | queue_unlock(q, *hb); |
| 1674 | |
| 1675 | ret = get_user(uval, uaddr); |
| 1676 | if (ret) |
| 1677 | goto out; |
| 1678 | |
| 1679 | if (!fshared) |
| 1680 | goto retry_private; |
| 1681 | |
| 1682 | put_futex_key(fshared, &q->key); |
| 1683 | goto retry; |
| 1684 | } |
| 1685 | |
| 1686 | if (uval != val) { |
| 1687 | queue_unlock(q, *hb); |
| 1688 | ret = -EWOULDBLOCK; |
| 1689 | } |
| 1690 | |
| 1691 | out: |
| 1692 | if (ret) |
| 1693 | put_futex_key(fshared, &q->key); |
| 1694 | return ret; |
| 1695 | } |
| 1696 | |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1697 | static int futex_wait(u32 __user *uaddr, int fshared, |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 1698 | u32 val, ktime_t *abs_time, u32 bitset, int clockrt) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1699 | { |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1700 | struct hrtimer_sleeper timeout, *to = NULL; |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1701 | struct restart_block *restart; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1702 | struct futex_hash_bucket *hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1703 | struct futex_q q; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1704 | int ret; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1705 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 1706 | if (!bitset) |
| 1707 | return -EINVAL; |
| 1708 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1709 | q.pi_state = NULL; |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 1710 | q.bitset = bitset; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1711 | q.rt_waiter = NULL; |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1712 | |
| 1713 | if (abs_time) { |
| 1714 | to = &timeout; |
| 1715 | |
| 1716 | hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME : |
| 1717 | CLOCK_MONOTONIC, HRTIMER_MODE_ABS); |
| 1718 | hrtimer_init_sleeper(to, current); |
| 1719 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, |
| 1720 | current->timer_slack_ns); |
| 1721 | } |
| 1722 | |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1723 | /* Prepare to wait on uaddr. */ |
| 1724 | ret = futex_wait_setup(uaddr, val, fshared, &q, &hb); |
| 1725 | if (ret) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1726 | goto out; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1727 | |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1728 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 1729 | futex_wait_queue_me(hb, &q, to); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1730 | |
| 1731 | /* If we were woken (and unqueued), we succeeded, whatever. */ |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1732 | ret = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1733 | if (!unqueue_me(&q)) |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1734 | goto out_put_key; |
| 1735 | ret = -ETIMEDOUT; |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1736 | if (to && !to->task) |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1737 | goto out_put_key; |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1738 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1739 | /* |
| 1740 | * We expect signal_pending(current), but another thread may |
| 1741 | * have handled it for us already. |
| 1742 | */ |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1743 | ret = -ERESTARTSYS; |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1744 | if (!abs_time) |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1745 | goto out_put_key; |
Steven Rostedt | ce6bd42 | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 1746 | |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1747 | restart = ¤t_thread_info()->restart_block; |
| 1748 | restart->fn = futex_wait_restart; |
| 1749 | restart->futex.uaddr = (u32 *)uaddr; |
| 1750 | restart->futex.val = val; |
| 1751 | restart->futex.time = abs_time->tv64; |
| 1752 | restart->futex.bitset = bitset; |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 1753 | restart->futex.flags = FLAGS_HAS_TIMEOUT; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1754 | |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 1755 | if (fshared) |
| 1756 | restart->futex.flags |= FLAGS_SHARED; |
| 1757 | if (clockrt) |
| 1758 | restart->futex.flags |= FLAGS_CLOCKRT; |
| 1759 | |
| 1760 | ret = -ERESTART_RESTARTBLOCK; |
| 1761 | |
| 1762 | out_put_key: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1763 | put_futex_key(fshared, &q.key); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1764 | out: |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1765 | if (to) { |
| 1766 | hrtimer_cancel(&to->timer); |
| 1767 | destroy_hrtimer_on_stack(&to->timer); |
| 1768 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1769 | return ret; |
| 1770 | } |
| 1771 | |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1772 | |
| 1773 | static long futex_wait_restart(struct restart_block *restart) |
| 1774 | { |
Steven Rostedt | ce6bd42 | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 1775 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1776 | int fshared = 0; |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 1777 | ktime_t t, *tp = NULL; |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1778 | |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 1779 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
| 1780 | t.tv64 = restart->futex.time; |
| 1781 | tp = &t; |
| 1782 | } |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1783 | restart->fn = do_no_restart_syscall; |
Steven Rostedt | ce6bd42 | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 1784 | if (restart->futex.flags & FLAGS_SHARED) |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1785 | fshared = 1; |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 1786 | return (long)futex_wait(uaddr, fshared, restart->futex.val, tp, |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 1787 | restart->futex.bitset, |
| 1788 | restart->futex.flags & FLAGS_CLOCKRT); |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1789 | } |
| 1790 | |
| 1791 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1792 | /* |
| 1793 | * Userspace tried a 0 -> TID atomic transition of the futex value |
| 1794 | * and failed. The kernel side here does the whole locking operation: |
| 1795 | * if there are waiters then it will block, it does PI, etc. (Due to |
| 1796 | * races the kernel might see a 0 value of the futex too.) |
| 1797 | */ |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1798 | static int futex_lock_pi(u32 __user *uaddr, int fshared, |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1799 | int detect, ktime_t *time, int trylock) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1800 | { |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 1801 | struct hrtimer_sleeper timeout, *to = NULL; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1802 | struct futex_hash_bucket *hb; |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 1803 | u32 uval; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1804 | struct futex_q q; |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1805 | int res, ret; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1806 | |
| 1807 | if (refill_pi_state_cache()) |
| 1808 | return -ENOMEM; |
| 1809 | |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1810 | if (time) { |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 1811 | to = &timeout; |
Thomas Gleixner | 237fc6e | 2008-04-30 00:55:04 -0700 | [diff] [blame] | 1812 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
| 1813 | HRTIMER_MODE_ABS); |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 1814 | hrtimer_init_sleeper(to, current); |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 1815 | hrtimer_set_expires(&to->timer, *time); |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 1816 | } |
| 1817 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1818 | q.pi_state = NULL; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1819 | q.rt_waiter = NULL; |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1820 | retry: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1821 | q.key = FUTEX_KEY_INIT; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1822 | ret = get_futex_key(uaddr, fshared, &q.key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1823 | if (unlikely(ret != 0)) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1824 | goto out; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1825 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1826 | retry_private: |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 1827 | hb = queue_lock(&q); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1828 | |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1829 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1830 | if (unlikely(ret)) { |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1831 | switch (ret) { |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 1832 | case 1: |
| 1833 | /* We got the lock. */ |
| 1834 | ret = 0; |
| 1835 | goto out_unlock_put_key; |
| 1836 | case -EFAULT: |
| 1837 | goto uaddr_faulted; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1838 | case -EAGAIN: |
| 1839 | /* |
| 1840 | * Task is exiting and we just wait for the |
| 1841 | * exit to complete. |
| 1842 | */ |
| 1843 | queue_unlock(&q, hb); |
Darren Hart | de87fcc | 2009-03-12 00:55:46 -0700 | [diff] [blame] | 1844 | put_futex_key(fshared, &q.key); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1845 | cond_resched(); |
| 1846 | goto retry; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1847 | default: |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1848 | goto out_unlock_put_key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1849 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1850 | } |
| 1851 | |
| 1852 | /* |
| 1853 | * Only actually queue now that the atomic ops are done: |
| 1854 | */ |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 1855 | queue_me(&q, hb); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1856 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1857 | WARN_ON(!q.pi_state); |
| 1858 | /* |
| 1859 | * Block on the PI mutex: |
| 1860 | */ |
| 1861 | if (!trylock) |
| 1862 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); |
| 1863 | else { |
| 1864 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); |
| 1865 | /* Fixup the trylock return value: */ |
| 1866 | ret = ret ? 0 : -EWOULDBLOCK; |
| 1867 | } |
| 1868 | |
Vernon Mauery | a99e4e4 | 2006-07-01 04:35:42 -0700 | [diff] [blame] | 1869 | spin_lock(q.lock_ptr); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1870 | /* |
| 1871 | * Fixup the pi_state owner and possibly acquire the lock if we |
| 1872 | * haven't already. |
| 1873 | */ |
| 1874 | res = fixup_owner(uaddr, fshared, &q, !ret); |
| 1875 | /* |
| 1876 | * If fixup_owner() returned an error, proprogate that. If it acquired |
| 1877 | * the lock, clear our -ETIMEDOUT or -EINTR. |
| 1878 | */ |
| 1879 | if (res) |
| 1880 | ret = (res < 0) ? res : 0; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1881 | |
Darren Hart | e8f6386 | 2009-03-12 00:56:06 -0700 | [diff] [blame] | 1882 | /* |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1883 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
| 1884 | * it and return the fault to userspace. |
Darren Hart | e8f6386 | 2009-03-12 00:56:06 -0700 | [diff] [blame] | 1885 | */ |
| 1886 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) |
| 1887 | rt_mutex_unlock(&q.pi_state->pi_mutex); |
| 1888 | |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1889 | /* Unqueue and drop the lock */ |
| 1890 | unqueue_me_pi(&q); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1891 | |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1892 | goto out; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1893 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1894 | out_unlock_put_key: |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1895 | queue_unlock(&q, hb); |
| 1896 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1897 | out_put_key: |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1898 | put_futex_key(fshared, &q.key); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1899 | out: |
Thomas Gleixner | 237fc6e | 2008-04-30 00:55:04 -0700 | [diff] [blame] | 1900 | if (to) |
| 1901 | destroy_hrtimer_on_stack(&to->timer); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1902 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1903 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1904 | uaddr_faulted: |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1905 | /* |
Darren Hart | b568636 | 2008-12-18 15:06:34 -0800 | [diff] [blame] | 1906 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
| 1907 | * atomically. Therefore, if we continue to fault after get_user() |
| 1908 | * below, we need to handle the fault ourselves, while still holding |
| 1909 | * the mmap_sem. This can occur if the uaddr is under contention as |
| 1910 | * we have to drop the mmap_sem in order to call get_user(). |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1911 | */ |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1912 | queue_unlock(&q, hb); |
| 1913 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1914 | ret = get_user(uval, uaddr); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1915 | if (ret) |
| 1916 | goto out_put_key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1917 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1918 | if (!fshared) |
| 1919 | goto retry_private; |
| 1920 | |
| 1921 | put_futex_key(fshared, &q.key); |
| 1922 | goto retry; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1923 | } |
| 1924 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1925 | static long futex_lock_pi_restart(struct restart_block *restart) |
| 1926 | { |
| 1927 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
| 1928 | ktime_t t, *tp = NULL; |
| 1929 | int fshared = restart->futex.flags & FLAGS_SHARED; |
| 1930 | |
| 1931 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
| 1932 | t.tv64 = restart->futex.time; |
| 1933 | tp = &t; |
| 1934 | } |
| 1935 | restart->fn = do_no_restart_syscall; |
| 1936 | |
| 1937 | return (long)futex_lock_pi(uaddr, fshared, restart->futex.val, tp, 0); |
| 1938 | } |
Darren Hart | de87fcc | 2009-03-12 00:55:46 -0700 | [diff] [blame] | 1939 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1940 | /* |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1941 | * Userspace attempted a TID -> 0 atomic transition, and failed. |
| 1942 | * This is the in-kernel slowpath: we look up the PI state (if any), |
| 1943 | * and do the rt-mutex unlock. |
| 1944 | */ |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 1945 | static int futex_unlock_pi(u32 __user *uaddr, int fshared) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1946 | { |
| 1947 | struct futex_hash_bucket *hb; |
| 1948 | struct futex_q *this, *next; |
| 1949 | u32 uval; |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1950 | struct plist_head *head; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1951 | union futex_key key = FUTEX_KEY_INIT; |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1952 | int ret; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1953 | |
| 1954 | retry: |
| 1955 | if (get_user(uval, uaddr)) |
| 1956 | return -EFAULT; |
| 1957 | /* |
| 1958 | * We release only a lock we actually own: |
| 1959 | */ |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 1960 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1961 | return -EPERM; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1962 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 1963 | ret = get_futex_key(uaddr, fshared, &key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1964 | if (unlikely(ret != 0)) |
| 1965 | goto out; |
| 1966 | |
| 1967 | hb = hash_futex(&key); |
| 1968 | spin_lock(&hb->lock); |
| 1969 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1970 | /* |
| 1971 | * To avoid races, try to do the TID -> 0 atomic transition |
| 1972 | * again. If it succeeds then we can return without waking |
| 1973 | * anyone else up: |
| 1974 | */ |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 1975 | if (!(uval & FUTEX_OWNER_DIED)) |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 1976 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 1977 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1978 | |
| 1979 | if (unlikely(uval == -EFAULT)) |
| 1980 | goto pi_faulted; |
| 1981 | /* |
| 1982 | * Rare case: we managed to release the lock atomically, |
| 1983 | * no need to wake anyone else up: |
| 1984 | */ |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 1985 | if (unlikely(uval == task_pid_vnr(current))) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1986 | goto out_unlock; |
| 1987 | |
| 1988 | /* |
| 1989 | * Ok, other tasks may need to be woken up - check waiters |
| 1990 | * and do the wakeup if necessary: |
| 1991 | */ |
| 1992 | head = &hb->chain; |
| 1993 | |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1994 | plist_for_each_entry_safe(this, next, head, list) { |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1995 | if (!match_futex (&this->key, &key)) |
| 1996 | continue; |
| 1997 | ret = wake_futex_pi(uaddr, uval, this); |
| 1998 | /* |
| 1999 | * The atomic access to the futex value |
| 2000 | * generated a pagefault, so retry the |
| 2001 | * user-access and the wakeup: |
| 2002 | */ |
| 2003 | if (ret == -EFAULT) |
| 2004 | goto pi_faulted; |
| 2005 | goto out_unlock; |
| 2006 | } |
| 2007 | /* |
| 2008 | * No waiters - kernel unlocks the futex: |
| 2009 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2010 | if (!(uval & FUTEX_OWNER_DIED)) { |
| 2011 | ret = unlock_futex_pi(uaddr, uval); |
| 2012 | if (ret == -EFAULT) |
| 2013 | goto pi_faulted; |
| 2014 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2015 | |
| 2016 | out_unlock: |
| 2017 | spin_unlock(&hb->lock); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 2018 | put_futex_key(fshared, &key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2019 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2020 | out: |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2021 | return ret; |
| 2022 | |
| 2023 | pi_faulted: |
| 2024 | /* |
Darren Hart | b568636 | 2008-12-18 15:06:34 -0800 | [diff] [blame] | 2025 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
| 2026 | * atomically. Therefore, if we continue to fault after get_user() |
| 2027 | * below, we need to handle the fault ourselves, while still holding |
| 2028 | * the mmap_sem. This can occur if the uaddr is under contention as |
| 2029 | * we have to drop the mmap_sem in order to call get_user(). |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2030 | */ |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2031 | spin_unlock(&hb->lock); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 2032 | put_futex_key(fshared, &key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2033 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2034 | ret = get_user(uval, uaddr); |
Darren Hart | b568636 | 2008-12-18 15:06:34 -0800 | [diff] [blame] | 2035 | if (!ret) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2036 | goto retry; |
| 2037 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2038 | return ret; |
| 2039 | } |
| 2040 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2041 | /** |
| 2042 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex |
| 2043 | * @hb: the hash_bucket futex_q was original enqueued on |
| 2044 | * @q: the futex_q woken while waiting to be requeued |
| 2045 | * @key2: the futex_key of the requeue target futex |
| 2046 | * @timeout: the timeout associated with the wait (NULL if none) |
| 2047 | * |
| 2048 | * Detect if the task was woken on the initial futex as opposed to the requeue |
| 2049 | * target futex. If so, determine if it was a timeout or a signal that caused |
| 2050 | * the wakeup and return the appropriate error code to the caller. Must be |
| 2051 | * called with the hb lock held. |
| 2052 | * |
| 2053 | * Returns |
| 2054 | * 0 - no early wakeup detected |
| 2055 | * <0 - -ETIMEDOUT or -ERESTARTSYS (FIXME: or ERESTARTNOINTR?) |
| 2056 | */ |
| 2057 | static inline |
| 2058 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, |
| 2059 | struct futex_q *q, union futex_key *key2, |
| 2060 | struct hrtimer_sleeper *timeout) |
| 2061 | { |
| 2062 | int ret = 0; |
| 2063 | |
| 2064 | /* |
| 2065 | * With the hb lock held, we avoid races while we process the wakeup. |
| 2066 | * We only need to hold hb (and not hb2) to ensure atomicity as the |
| 2067 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. |
| 2068 | * It can't be requeued from uaddr2 to something else since we don't |
| 2069 | * support a PI aware source futex for requeue. |
| 2070 | */ |
| 2071 | if (!match_futex(&q->key, key2)) { |
| 2072 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); |
| 2073 | /* |
| 2074 | * We were woken prior to requeue by a timeout or a signal. |
| 2075 | * Unqueue the futex_q and determine which it was. |
| 2076 | */ |
| 2077 | plist_del(&q->list, &q->list.plist); |
| 2078 | drop_futex_key_refs(&q->key); |
| 2079 | |
| 2080 | if (timeout && !timeout->task) |
| 2081 | ret = -ETIMEDOUT; |
| 2082 | else { |
| 2083 | /* |
| 2084 | * We expect signal_pending(current), but another |
| 2085 | * thread may have handled it for us already. |
| 2086 | */ |
| 2087 | /* FIXME: ERESTARTSYS or ERESTARTNOINTR? Do we care if |
| 2088 | * the user specified SA_RESTART or not? */ |
| 2089 | ret = -ERESTARTSYS; |
| 2090 | } |
| 2091 | } |
| 2092 | return ret; |
| 2093 | } |
| 2094 | |
| 2095 | /** |
| 2096 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 |
| 2097 | * @uaddr: the futex we initialyl wait on (non-pi) |
| 2098 | * @fshared: whether the futexes are shared (1) or not (0). They must be |
| 2099 | * the same type, no requeueing from private to shared, etc. |
| 2100 | * @val: the expected value of uaddr |
| 2101 | * @abs_time: absolute timeout |
| 2102 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all. |
| 2103 | * @clockrt: whether to use CLOCK_REALTIME (1) or CLOCK_MONOTONIC (0) |
| 2104 | * @uaddr2: the pi futex we will take prior to returning to user-space |
| 2105 | * |
| 2106 | * The caller will wait on uaddr and will be requeued by futex_requeue() to |
| 2107 | * uaddr2 which must be PI aware. Normal wakeup will wake on uaddr2 and |
| 2108 | * complete the acquisition of the rt_mutex prior to returning to userspace. |
| 2109 | * This ensures the rt_mutex maintains an owner when it has waiters; without |
| 2110 | * one, the pi logic wouldn't know which task to boost/deboost, if there was a |
| 2111 | * need to. |
| 2112 | * |
| 2113 | * We call schedule in futex_wait_queue_me() when we enqueue and return there |
| 2114 | * via the following: |
| 2115 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() |
| 2116 | * 2) wakeup on uaddr2 after a requeue and subsequent unlock |
| 2117 | * 3) signal (before or after requeue) |
| 2118 | * 4) timeout (before or after requeue) |
| 2119 | * |
| 2120 | * If 3, we setup a restart_block with futex_wait_requeue_pi() as the function. |
| 2121 | * |
| 2122 | * If 2, we may then block on trying to take the rt_mutex and return via: |
| 2123 | * 5) successful lock |
| 2124 | * 6) signal |
| 2125 | * 7) timeout |
| 2126 | * 8) other lock acquisition failure |
| 2127 | * |
| 2128 | * If 6, we setup a restart_block with futex_lock_pi() as the function. |
| 2129 | * |
| 2130 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. |
| 2131 | * |
| 2132 | * Returns: |
| 2133 | * 0 - On success |
| 2134 | * <0 - On error |
| 2135 | */ |
| 2136 | static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared, |
| 2137 | u32 val, ktime_t *abs_time, u32 bitset, |
| 2138 | int clockrt, u32 __user *uaddr2) |
| 2139 | { |
| 2140 | struct hrtimer_sleeper timeout, *to = NULL; |
| 2141 | struct rt_mutex_waiter rt_waiter; |
| 2142 | struct rt_mutex *pi_mutex = NULL; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2143 | struct restart_block *restart; |
| 2144 | struct futex_hash_bucket *hb; |
| 2145 | union futex_key key2; |
| 2146 | struct futex_q q; |
| 2147 | int res, ret; |
| 2148 | u32 uval; |
| 2149 | |
| 2150 | if (!bitset) |
| 2151 | return -EINVAL; |
| 2152 | |
| 2153 | if (abs_time) { |
| 2154 | to = &timeout; |
| 2155 | hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME : |
| 2156 | CLOCK_MONOTONIC, HRTIMER_MODE_ABS); |
| 2157 | hrtimer_init_sleeper(to, current); |
| 2158 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, |
| 2159 | current->timer_slack_ns); |
| 2160 | } |
| 2161 | |
| 2162 | /* |
| 2163 | * The waiter is allocated on our stack, manipulated by the requeue |
| 2164 | * code while we sleep on uaddr. |
| 2165 | */ |
| 2166 | debug_rt_mutex_init_waiter(&rt_waiter); |
| 2167 | rt_waiter.task = NULL; |
| 2168 | |
| 2169 | q.pi_state = NULL; |
| 2170 | q.bitset = bitset; |
| 2171 | q.rt_waiter = &rt_waiter; |
| 2172 | |
| 2173 | key2 = FUTEX_KEY_INIT; |
| 2174 | ret = get_futex_key(uaddr2, fshared, &key2); |
| 2175 | if (unlikely(ret != 0)) |
| 2176 | goto out; |
| 2177 | |
| 2178 | /* Prepare to wait on uaddr. */ |
| 2179 | ret = futex_wait_setup(uaddr, val, fshared, &q, &hb); |
| 2180 | if (ret) { |
| 2181 | put_futex_key(fshared, &key2); |
| 2182 | goto out; |
| 2183 | } |
| 2184 | |
| 2185 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame^] | 2186 | futex_wait_queue_me(hb, &q, to); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2187 | |
| 2188 | spin_lock(&hb->lock); |
| 2189 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); |
| 2190 | spin_unlock(&hb->lock); |
| 2191 | if (ret) |
| 2192 | goto out_put_keys; |
| 2193 | |
| 2194 | /* |
| 2195 | * In order for us to be here, we know our q.key == key2, and since |
| 2196 | * we took the hb->lock above, we also know that futex_requeue() has |
| 2197 | * completed and we no longer have to concern ourselves with a wakeup |
| 2198 | * race with the atomic proxy lock acquition by the requeue code. |
| 2199 | */ |
| 2200 | |
| 2201 | /* Check if the requeue code acquired the second futex for us. */ |
| 2202 | if (!q.rt_waiter) { |
| 2203 | /* |
| 2204 | * Got the lock. We might not be the anticipated owner if we |
| 2205 | * did a lock-steal - fix up the PI-state in that case. |
| 2206 | */ |
| 2207 | if (q.pi_state && (q.pi_state->owner != current)) { |
| 2208 | spin_lock(q.lock_ptr); |
| 2209 | ret = fixup_pi_state_owner(uaddr2, &q, current, |
| 2210 | fshared); |
| 2211 | spin_unlock(q.lock_ptr); |
| 2212 | } |
| 2213 | } else { |
| 2214 | /* |
| 2215 | * We have been woken up by futex_unlock_pi(), a timeout, or a |
| 2216 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor |
| 2217 | * the pi_state. |
| 2218 | */ |
| 2219 | WARN_ON(!&q.pi_state); |
| 2220 | pi_mutex = &q.pi_state->pi_mutex; |
| 2221 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); |
| 2222 | debug_rt_mutex_free_waiter(&rt_waiter); |
| 2223 | |
| 2224 | spin_lock(q.lock_ptr); |
| 2225 | /* |
| 2226 | * Fixup the pi_state owner and possibly acquire the lock if we |
| 2227 | * haven't already. |
| 2228 | */ |
| 2229 | res = fixup_owner(uaddr2, fshared, &q, !ret); |
| 2230 | /* |
| 2231 | * If fixup_owner() returned an error, proprogate that. If it |
| 2232 | * acquired the lock, clear our -ETIMEDOUT or -EINTR. |
| 2233 | */ |
| 2234 | if (res) |
| 2235 | ret = (res < 0) ? res : 0; |
| 2236 | |
| 2237 | /* Unqueue and drop the lock. */ |
| 2238 | unqueue_me_pi(&q); |
| 2239 | } |
| 2240 | |
| 2241 | /* |
| 2242 | * If fixup_pi_state_owner() faulted and was unable to handle the |
| 2243 | * fault, unlock the rt_mutex and return the fault to userspace. |
| 2244 | */ |
| 2245 | if (ret == -EFAULT) { |
| 2246 | if (rt_mutex_owner(pi_mutex) == current) |
| 2247 | rt_mutex_unlock(pi_mutex); |
| 2248 | } else if (ret == -EINTR) { |
| 2249 | ret = -EFAULT; |
| 2250 | if (get_user(uval, uaddr2)) |
| 2251 | goto out_put_keys; |
| 2252 | |
| 2253 | /* |
| 2254 | * We've already been requeued, so restart by calling |
| 2255 | * futex_lock_pi() directly, rather then returning to this |
| 2256 | * function. |
| 2257 | */ |
| 2258 | ret = -ERESTART_RESTARTBLOCK; |
| 2259 | restart = ¤t_thread_info()->restart_block; |
| 2260 | restart->fn = futex_lock_pi_restart; |
| 2261 | restart->futex.uaddr = (u32 *)uaddr2; |
| 2262 | restart->futex.val = uval; |
| 2263 | restart->futex.flags = 0; |
| 2264 | if (abs_time) { |
| 2265 | restart->futex.flags |= FLAGS_HAS_TIMEOUT; |
| 2266 | restart->futex.time = abs_time->tv64; |
| 2267 | } |
| 2268 | |
| 2269 | if (fshared) |
| 2270 | restart->futex.flags |= FLAGS_SHARED; |
| 2271 | if (clockrt) |
| 2272 | restart->futex.flags |= FLAGS_CLOCKRT; |
| 2273 | } |
| 2274 | |
| 2275 | out_put_keys: |
| 2276 | put_futex_key(fshared, &q.key); |
| 2277 | put_futex_key(fshared, &key2); |
| 2278 | |
| 2279 | out: |
| 2280 | if (to) { |
| 2281 | hrtimer_cancel(&to->timer); |
| 2282 | destroy_hrtimer_on_stack(&to->timer); |
| 2283 | } |
| 2284 | return ret; |
| 2285 | } |
| 2286 | |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2287 | /* |
| 2288 | * Support for robust futexes: the kernel cleans up held futexes at |
| 2289 | * thread exit time. |
| 2290 | * |
| 2291 | * Implementation: user-space maintains a per-thread list of locks it |
| 2292 | * is holding. Upon do_exit(), the kernel carefully walks this list, |
| 2293 | * and marks all locks that are owned by this thread with the |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2294 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2295 | * always manipulated with the lock held, so the list is private and |
| 2296 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' |
| 2297 | * field, to allow the kernel to clean up if the thread dies after |
| 2298 | * acquiring the lock, but just before it could have added itself to |
| 2299 | * the list. There can only be one such pending lock. |
| 2300 | */ |
| 2301 | |
| 2302 | /** |
| 2303 | * sys_set_robust_list - set the robust-futex list head of a task |
| 2304 | * @head: pointer to the list-head |
| 2305 | * @len: length of the list-head, as userspace expects |
| 2306 | */ |
Heiko Carstens | 836f92a | 2009-01-14 14:14:33 +0100 | [diff] [blame] | 2307 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
| 2308 | size_t, len) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2309 | { |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2310 | if (!futex_cmpxchg_enabled) |
| 2311 | return -ENOSYS; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2312 | /* |
| 2313 | * The kernel knows only one size for now: |
| 2314 | */ |
| 2315 | if (unlikely(len != sizeof(*head))) |
| 2316 | return -EINVAL; |
| 2317 | |
| 2318 | current->robust_list = head; |
| 2319 | |
| 2320 | return 0; |
| 2321 | } |
| 2322 | |
| 2323 | /** |
| 2324 | * sys_get_robust_list - get the robust-futex list head of a task |
| 2325 | * @pid: pid of the process [zero for current task] |
| 2326 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in |
| 2327 | * @len_ptr: pointer to a length field, the kernel fills in the header size |
| 2328 | */ |
Heiko Carstens | 836f92a | 2009-01-14 14:14:33 +0100 | [diff] [blame] | 2329 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
| 2330 | struct robust_list_head __user * __user *, head_ptr, |
| 2331 | size_t __user *, len_ptr) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2332 | { |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2333 | struct robust_list_head __user *head; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2334 | unsigned long ret; |
David Howells | c69e8d9 | 2008-11-14 10:39:19 +1100 | [diff] [blame] | 2335 | const struct cred *cred = current_cred(), *pcred; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2336 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2337 | if (!futex_cmpxchg_enabled) |
| 2338 | return -ENOSYS; |
| 2339 | |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2340 | if (!pid) |
| 2341 | head = current->robust_list; |
| 2342 | else { |
| 2343 | struct task_struct *p; |
| 2344 | |
| 2345 | ret = -ESRCH; |
Oleg Nesterov | aaa2a97 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 2346 | rcu_read_lock(); |
Pavel Emelyanov | 228ebcb | 2007-10-18 23:40:16 -0700 | [diff] [blame] | 2347 | p = find_task_by_vpid(pid); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2348 | if (!p) |
| 2349 | goto err_unlock; |
| 2350 | ret = -EPERM; |
David Howells | c69e8d9 | 2008-11-14 10:39:19 +1100 | [diff] [blame] | 2351 | pcred = __task_cred(p); |
| 2352 | if (cred->euid != pcred->euid && |
| 2353 | cred->euid != pcred->uid && |
David Howells | 76aac0e | 2008-11-14 10:39:12 +1100 | [diff] [blame] | 2354 | !capable(CAP_SYS_PTRACE)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2355 | goto err_unlock; |
| 2356 | head = p->robust_list; |
Oleg Nesterov | aaa2a97 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 2357 | rcu_read_unlock(); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2358 | } |
| 2359 | |
| 2360 | if (put_user(sizeof(*head), len_ptr)) |
| 2361 | return -EFAULT; |
| 2362 | return put_user(head, head_ptr); |
| 2363 | |
| 2364 | err_unlock: |
Oleg Nesterov | aaa2a97 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 2365 | rcu_read_unlock(); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2366 | |
| 2367 | return ret; |
| 2368 | } |
| 2369 | |
| 2370 | /* |
| 2371 | * Process a futex-list entry, check whether it's owned by the |
| 2372 | * dying task, and do notification if so: |
| 2373 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2374 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2375 | { |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2376 | u32 uval, nval, mval; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2377 | |
Ingo Molnar | 8f17d3a | 2006-03-27 01:16:27 -0800 | [diff] [blame] | 2378 | retry: |
| 2379 | if (get_user(uval, uaddr)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2380 | return -1; |
| 2381 | |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 2382 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2383 | /* |
| 2384 | * Ok, this dying thread is truly holding a futex |
| 2385 | * of interest. Set the OWNER_DIED bit atomically |
| 2386 | * via cmpxchg, and if the value had FUTEX_WAITERS |
| 2387 | * set, wake up a waiter (if any). (We have to do a |
| 2388 | * futex_wake() even if OWNER_DIED is already set - |
| 2389 | * to handle the rare but possible case of recursive |
| 2390 | * thread-death.) The rest of the cleanup is done in |
| 2391 | * userspace. |
| 2392 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2393 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
| 2394 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); |
| 2395 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2396 | if (nval == -EFAULT) |
| 2397 | return -1; |
| 2398 | |
| 2399 | if (nval != uval) |
Ingo Molnar | 8f17d3a | 2006-03-27 01:16:27 -0800 | [diff] [blame] | 2400 | goto retry; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2401 | |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2402 | /* |
| 2403 | * Wake robust non-PI futexes here. The wakeup of |
| 2404 | * PI futexes happens in exit_pi_state(): |
| 2405 | */ |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 2406 | if (!pi && (uval & FUTEX_WAITERS)) |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 2407 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2408 | } |
| 2409 | return 0; |
| 2410 | } |
| 2411 | |
| 2412 | /* |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2413 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: |
| 2414 | */ |
| 2415 | static inline int fetch_robust_entry(struct robust_list __user **entry, |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2416 | struct robust_list __user * __user *head, |
| 2417 | int *pi) |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2418 | { |
| 2419 | unsigned long uentry; |
| 2420 | |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2421 | if (get_user(uentry, (unsigned long __user *)head)) |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2422 | return -EFAULT; |
| 2423 | |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2424 | *entry = (void __user *)(uentry & ~1UL); |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2425 | *pi = uentry & 1; |
| 2426 | |
| 2427 | return 0; |
| 2428 | } |
| 2429 | |
| 2430 | /* |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2431 | * Walk curr->robust_list (very carefully, it's a userspace list!) |
| 2432 | * and mark any locks found there dead, and notify any waiters. |
| 2433 | * |
| 2434 | * We silently return on any sign of list-walking problem. |
| 2435 | */ |
| 2436 | void exit_robust_list(struct task_struct *curr) |
| 2437 | { |
| 2438 | struct robust_list_head __user *head = curr->robust_list; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2439 | struct robust_list __user *entry, *next_entry, *pending; |
| 2440 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2441 | unsigned long futex_offset; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2442 | int rc; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2443 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2444 | if (!futex_cmpxchg_enabled) |
| 2445 | return; |
| 2446 | |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2447 | /* |
| 2448 | * Fetch the list head (which was registered earlier, via |
| 2449 | * sys_set_robust_list()): |
| 2450 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2451 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2452 | return; |
| 2453 | /* |
| 2454 | * Fetch the relative futex offset: |
| 2455 | */ |
| 2456 | if (get_user(futex_offset, &head->futex_offset)) |
| 2457 | return; |
| 2458 | /* |
| 2459 | * Fetch any possibly pending lock-add first, and handle it |
| 2460 | * if it exists: |
| 2461 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2462 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2463 | return; |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2464 | |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2465 | next_entry = NULL; /* avoid warning with gcc */ |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2466 | while (entry != &head->list) { |
| 2467 | /* |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2468 | * Fetch the next entry in the list before calling |
| 2469 | * handle_futex_death: |
| 2470 | */ |
| 2471 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); |
| 2472 | /* |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2473 | * A pending lock might already be on the list, so |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2474 | * don't process it twice: |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2475 | */ |
| 2476 | if (entry != pending) |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2477 | if (handle_futex_death((void __user *)entry + futex_offset, |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2478 | curr, pi)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2479 | return; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2480 | if (rc) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2481 | return; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2482 | entry = next_entry; |
| 2483 | pi = next_pi; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2484 | /* |
| 2485 | * Avoid excessively long or circular lists: |
| 2486 | */ |
| 2487 | if (!--limit) |
| 2488 | break; |
| 2489 | |
| 2490 | cond_resched(); |
| 2491 | } |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2492 | |
| 2493 | if (pending) |
| 2494 | handle_futex_death((void __user *)pending + futex_offset, |
| 2495 | curr, pip); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2496 | } |
| 2497 | |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2498 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2499 | u32 __user *uaddr2, u32 val2, u32 val3) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2500 | { |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 2501 | int clockrt, ret = -ENOSYS; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2502 | int cmd = op & FUTEX_CMD_MASK; |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 2503 | int fshared = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2504 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2505 | if (!(op & FUTEX_PRIVATE_FLAG)) |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 2506 | fshared = 1; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2507 | |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 2508 | clockrt = op & FUTEX_CLOCK_REALTIME; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2509 | if (clockrt && cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 2510 | return -ENOSYS; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2511 | |
| 2512 | switch (cmd) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2513 | case FUTEX_WAIT: |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2514 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2515 | case FUTEX_WAIT_BITSET: |
Thomas Gleixner | 1acdac1 | 2008-11-20 10:02:53 -0800 | [diff] [blame] | 2516 | ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2517 | break; |
| 2518 | case FUTEX_WAKE: |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2519 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2520 | case FUTEX_WAKE_BITSET: |
| 2521 | ret = futex_wake(uaddr, fshared, val, val3); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2522 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2523 | case FUTEX_REQUEUE: |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2524 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL, 0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2525 | break; |
| 2526 | case FUTEX_CMP_REQUEUE: |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2527 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3, |
| 2528 | 0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2529 | break; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 2530 | case FUTEX_WAKE_OP: |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2531 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 2532 | break; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2533 | case FUTEX_LOCK_PI: |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2534 | if (futex_cmpxchg_enabled) |
| 2535 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2536 | break; |
| 2537 | case FUTEX_UNLOCK_PI: |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2538 | if (futex_cmpxchg_enabled) |
| 2539 | ret = futex_unlock_pi(uaddr, fshared); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2540 | break; |
| 2541 | case FUTEX_TRYLOCK_PI: |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2542 | if (futex_cmpxchg_enabled) |
| 2543 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2544 | break; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2545 | case FUTEX_WAIT_REQUEUE_PI: |
| 2546 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2547 | ret = futex_wait_requeue_pi(uaddr, fshared, val, timeout, val3, |
| 2548 | clockrt, uaddr2); |
| 2549 | break; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2550 | case FUTEX_CMP_REQUEUE_PI: |
| 2551 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3, |
| 2552 | 1); |
| 2553 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2554 | default: |
| 2555 | ret = -ENOSYS; |
| 2556 | } |
| 2557 | return ret; |
| 2558 | } |
| 2559 | |
| 2560 | |
Heiko Carstens | 17da2bd | 2009-01-14 14:14:10 +0100 | [diff] [blame] | 2561 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
| 2562 | struct timespec __user *, utime, u32 __user *, uaddr2, |
| 2563 | u32, val3) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2564 | { |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2565 | struct timespec ts; |
| 2566 | ktime_t t, *tp = NULL; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2567 | u32 val2 = 0; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2568 | int cmd = op & FUTEX_CMD_MASK; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2569 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2570 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2571 | cmd == FUTEX_WAIT_BITSET || |
| 2572 | cmd == FUTEX_WAIT_REQUEUE_PI)) { |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2573 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2574 | return -EFAULT; |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2575 | if (!timespec_valid(&ts)) |
Thomas Gleixner | 9741ef96 | 2006-03-31 02:31:32 -0800 | [diff] [blame] | 2576 | return -EINVAL; |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2577 | |
| 2578 | t = timespec_to_ktime(ts); |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2579 | if (cmd == FUTEX_WAIT) |
Thomas Gleixner | 5a7780e | 2008-02-13 09:20:43 +0100 | [diff] [blame] | 2580 | t = ktime_add_safe(ktime_get(), t); |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2581 | tp = &t; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2582 | } |
| 2583 | /* |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2584 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
Andreas Schwab | f54f098 | 2007-07-31 00:38:51 -0700 | [diff] [blame] | 2585 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2586 | */ |
Andreas Schwab | f54f098 | 2007-07-31 00:38:51 -0700 | [diff] [blame] | 2587 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
Darren Hart | ba9c22f | 2009-04-20 22:22:22 -0700 | [diff] [blame] | 2588 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2589 | val2 = (u32) (unsigned long) utime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2590 | |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2591 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2592 | } |
| 2593 | |
Benjamin Herrenschmidt | f6d107f | 2008-03-27 14:52:15 +1100 | [diff] [blame] | 2594 | static int __init futex_init(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2595 | { |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2596 | u32 curval; |
Thomas Gleixner | 3e4ab74 | 2008-02-23 15:23:55 -0800 | [diff] [blame] | 2597 | int i; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2598 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2599 | /* |
| 2600 | * This will fail and we want it. Some arch implementations do |
| 2601 | * runtime detection of the futex_atomic_cmpxchg_inatomic() |
| 2602 | * functionality. We want to know that before we call in any |
| 2603 | * of the complex code paths. Also we want to prevent |
| 2604 | * registration of robust lists in that case. NULL is |
| 2605 | * guaranteed to fault and we get -EFAULT on functional |
| 2606 | * implementation, the non functional ones will return |
| 2607 | * -ENOSYS. |
| 2608 | */ |
| 2609 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); |
| 2610 | if (curval == -EFAULT) |
| 2611 | futex_cmpxchg_enabled = 1; |
| 2612 | |
Thomas Gleixner | 3e4ab74 | 2008-02-23 15:23:55 -0800 | [diff] [blame] | 2613 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
| 2614 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); |
| 2615 | spin_lock_init(&futex_queues[i].lock); |
| 2616 | } |
| 2617 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2618 | return 0; |
| 2619 | } |
Benjamin Herrenschmidt | f6d107f | 2008-03-27 14:52:15 +1100 | [diff] [blame] | 2620 | __initcall(futex_init); |