blob: 8e3c3ffe1b9a57ea0110b36c089a5131760d0314 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 Molnar0771dfe2006-03-27 01:16:22 -080011 * 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 Molnarc87e2832006-06-27 02:54:58 -070015 * 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 Dumazet34f01cc2007-05-09 02:35:04 -070019 * PRIVATE futexes by Eric Dumazet
20 * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
21 *
Darren Hart52400ba2009-04-03 13:40:49 -070022 * 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 Torvalds1da177e2005-04-16 15:20:36 -070026 * 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 Juhl7ed20e12005-05-01 08:59:14 -070057#include <linux/signal.h>
Rusty Russell9adef582007-05-08 00:26:42 -070058#include <linux/module.h>
Andrey Mirkinfd5eea42007-10-16 23:30:13 -070059#include <linux/magic.h>
Pavel Emelyanovb4888932007-10-18 23:40:14 -070060#include <linux/pid.h>
61#include <linux/nsproxy.h>
62
Jakub Jelinek4732efb2005-09-06 15:16:25 -070063#include <asm/futex.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070064
Ingo Molnarc87e2832006-06-27 02:54:58 -070065#include "rtmutex_common.h"
66
Thomas Gleixnera0c1e902008-02-23 15:23:57 -080067int __read_mostly futex_cmpxchg_enabled;
68
Linus Torvalds1da177e2005-04-16 15:20:36 -070069#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
70
71/*
Ingo Molnarc87e2832006-06-27 02:54:58 -070072 * Priority Inheritance state:
73 */
74struct 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
Darren Hartd8d88fb2009-09-21 22:30:30 -070092/**
93 * struct futex_q - The hashed futex queue entry, one per waiting task
94 * @task: the task waiting on the futex
95 * @lock_ptr: the hash bucket lock
96 * @key: the key the futex is hashed on
97 * @pi_state: optional priority inheritance state
98 * @rt_waiter: rt_waiter storage for use with requeue_pi
99 * @requeue_pi_key: the requeue_pi target futex key
100 * @bitset: bitset for the optional bitmasked wakeup
101 *
102 * We use this hashed waitqueue, instead of a normal wait_queue_t, so
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 * we can wake only the relevant ones (hashed queues may be shared).
104 *
105 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
Pierre Peifferec92d082007-05-09 02:35:00 -0700106 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 * The order of wakup is always to make the first condition true, then
Darren Hartd8d88fb2009-09-21 22:30:30 -0700108 * the second.
109 *
110 * PI futexes are typically woken before they are removed from the hash list via
111 * the rt_mutex code. See unqueue_me_pi().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 */
113struct futex_q {
Pierre Peifferec92d082007-05-09 02:35:00 -0700114 struct plist_node list;
Darren Hartd8d88fb2009-09-21 22:30:30 -0700115
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +0200116 struct task_struct *task;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117 spinlock_t *lock_ptr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 union futex_key key;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700119 struct futex_pi_state *pi_state;
Darren Hart52400ba2009-04-03 13:40:49 -0700120 struct rt_mutex_waiter *rt_waiter;
Darren Hart84bc4af2009-08-13 17:36:53 -0700121 union futex_key *requeue_pi_key;
Thomas Gleixnercd689982008-02-01 17:45:14 +0100122 u32 bitset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123};
124
125/*
Darren Hartb2d09942009-03-12 00:55:37 -0700126 * Hash buckets are shared by all the futex_keys that hash to the same
127 * location. Each key may have multiple futex_q structures, one for each task
128 * waiting on a futex.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129 */
130struct futex_hash_bucket {
Pierre Peifferec92d082007-05-09 02:35:00 -0700131 spinlock_t lock;
132 struct plist_head chain;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133};
134
135static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
136
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137/*
138 * We hash on the keys returned from get_futex_key (see below).
139 */
140static struct futex_hash_bucket *hash_futex(union futex_key *key)
141{
142 u32 hash = jhash2((u32*)&key->both.word,
143 (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
144 key->both.offset);
145 return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
146}
147
148/*
149 * Return 1 if two futex_keys are equal, 0 otherwise.
150 */
151static inline int match_futex(union futex_key *key1, union futex_key *key2)
152{
Darren Hart2bc87202009-10-14 10:12:39 -0700153 return (key1 && key2
154 && key1->both.word == key2->both.word
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 && key1->both.ptr == key2->both.ptr
156 && key1->both.offset == key2->both.offset);
157}
158
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200159/*
160 * Take a reference to the resource addressed by a key.
161 * Can be called while holding spinlocks.
162 *
163 */
164static void get_futex_key_refs(union futex_key *key)
165{
166 if (!key->both.ptr)
167 return;
168
169 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
170 case FUT_OFF_INODE:
171 atomic_inc(&key->shared.inode->i_count);
172 break;
173 case FUT_OFF_MMSHARED:
174 atomic_inc(&key->private.mm->mm_count);
175 break;
176 }
177}
178
179/*
180 * Drop a reference to the resource addressed by a key.
181 * The hash bucket spinlock must not be held.
182 */
183static void drop_futex_key_refs(union futex_key *key)
184{
Darren Hart90621c42008-12-29 19:43:21 -0800185 if (!key->both.ptr) {
186 /* If we're here then we tried to put a key we failed to get */
187 WARN_ON_ONCE(1);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200188 return;
Darren Hart90621c42008-12-29 19:43:21 -0800189 }
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200190
191 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
192 case FUT_OFF_INODE:
193 iput(key->shared.inode);
194 break;
195 case FUT_OFF_MMSHARED:
196 mmdrop(key->private.mm);
197 break;
198 }
199}
200
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700201/**
Darren Hartd96ee562009-09-21 22:30:22 -0700202 * get_futex_key() - Get parameters which are the keys for a futex
203 * @uaddr: virtual address of the futex
204 * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
205 * @key: address where result is stored.
206 * @rw: mapping needs to be read/write (values: VERIFY_READ,
207 * VERIFY_WRITE)
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700208 *
209 * Returns a negative error code or 0
210 * The key words are stored in *key on success.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211 *
Josef "Jeff" Sipekf3a43f32006-12-08 02:36:43 -0800212 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 * offset_within_page). For private mappings, it's (uaddr, current->mm).
214 * We can usually work out the index without swapping in the page.
215 *
Darren Hartb2d09942009-03-12 00:55:37 -0700216 * lock_page() might sleep, the caller should not hold a spinlock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 */
Thomas Gleixner64d13042009-05-18 21:20:10 +0200218static int
219get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220{
Ingo Molnare2970f22006-06-27 02:54:47 -0700221 unsigned long address = (unsigned long)uaddr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222 struct mm_struct *mm = current->mm;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223 struct page *page;
224 int err;
225
226 /*
227 * The futex address must be "naturally" aligned.
228 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700229 key->both.offset = address % PAGE_SIZE;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700230 if (unlikely((address % sizeof(u32)) != 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231 return -EINVAL;
Ingo Molnare2970f22006-06-27 02:54:47 -0700232 address -= key->both.offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233
234 /*
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700235 * PROCESS_PRIVATE futexes are fast.
236 * As the mm cannot disappear under us and the 'key' only needs
237 * virtual address, we dont even have to find the underlying vma.
238 * Note : We do have to check 'uaddr' is a valid user address,
239 * but access_ok() should be faster than find_vma()
240 */
241 if (!fshared) {
Thomas Gleixner64d13042009-05-18 21:20:10 +0200242 if (unlikely(!access_ok(rw, uaddr, sizeof(u32))))
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700243 return -EFAULT;
244 key->private.mm = mm;
245 key->private.address = address;
Peter Zijlstra42569c32008-09-30 12:33:07 +0200246 get_futex_key_refs(key);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700247 return 0;
248 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200250again:
Thomas Gleixner64d13042009-05-18 21:20:10 +0200251 err = get_user_pages_fast(address, 1, rw == VERIFY_WRITE, &page);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200252 if (err < 0)
253 return err;
254
Sonny Raoce2ae532009-07-10 18:13:13 -0500255 page = compound_head(page);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200256 lock_page(page);
257 if (!page->mapping) {
258 unlock_page(page);
259 put_page(page);
260 goto again;
261 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262
263 /*
264 * Private mappings are handled in a simple way.
265 *
266 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
267 * it's a read-only handle, it's expected that futexes attach to
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200268 * the object not the particular process.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 */
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200270 if (PageAnon(page)) {
271 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272 key->private.mm = mm;
Ingo Molnare2970f22006-06-27 02:54:47 -0700273 key->private.address = address;
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200274 } else {
275 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
276 key->shared.inode = page->mapping->host;
277 key->shared.pgoff = page->index;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700278 }
279
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200280 get_futex_key_refs(key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200282 unlock_page(page);
283 put_page(page);
284 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285}
286
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200287static inline
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200288void put_futex_key(int fshared, union futex_key *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289{
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200290 drop_futex_key_refs(key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291}
292
Darren Hartd96ee562009-09-21 22:30:22 -0700293/**
294 * fault_in_user_writeable() - Fault in user address and verify RW access
Thomas Gleixnerd0725992009-06-11 23:15:43 +0200295 * @uaddr: pointer to faulting user space address
296 *
297 * Slow path to fixup the fault we just took in the atomic write
298 * access to @uaddr.
299 *
300 * We have no generic implementation of a non destructive write to the
301 * user address. We know that we faulted in the atomic pagefault
302 * disabled section so we can as well avoid the #PF overhead by
303 * calling get_user_pages() right away.
304 */
305static int fault_in_user_writeable(u32 __user *uaddr)
306{
Andi Kleen722d0172009-12-08 13:19:42 +0100307 struct mm_struct *mm = current->mm;
308 int ret;
309
310 down_read(&mm->mmap_sem);
311 ret = get_user_pages(current, mm, (unsigned long)uaddr,
312 1, 1, 0, NULL, NULL);
313 up_read(&mm->mmap_sem);
314
Thomas Gleixnerd0725992009-06-11 23:15:43 +0200315 return ret < 0 ? ret : 0;
316}
317
Darren Hart4b1c4862009-04-03 13:39:42 -0700318/**
319 * futex_top_waiter() - Return the highest priority waiter on a futex
Darren Hartd96ee562009-09-21 22:30:22 -0700320 * @hb: the hash bucket the futex_q's reside in
321 * @key: the futex key (to distinguish it from other futex futex_q's)
Darren Hart4b1c4862009-04-03 13:39:42 -0700322 *
323 * Must be called with the hb lock held.
324 */
325static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb,
326 union futex_key *key)
327{
328 struct futex_q *this;
329
330 plist_for_each_entry(this, &hb->chain, list) {
331 if (match_futex(&this->key, key))
332 return this;
333 }
334 return NULL;
335}
336
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700337static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
338{
339 u32 curval;
340
341 pagefault_disable();
342 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
343 pagefault_enable();
344
345 return curval;
346}
347
348static int get_futex_value_locked(u32 *dest, u32 __user *from)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349{
350 int ret;
351
Peter Zijlstraa8663742006-12-06 20:32:20 -0800352 pagefault_disable();
Ingo Molnare2970f22006-06-27 02:54:47 -0700353 ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
Peter Zijlstraa8663742006-12-06 20:32:20 -0800354 pagefault_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700355
356 return ret ? -EFAULT : 0;
357}
358
Ingo Molnarc87e2832006-06-27 02:54:58 -0700359
360/*
361 * PI code:
362 */
363static int refill_pi_state_cache(void)
364{
365 struct futex_pi_state *pi_state;
366
367 if (likely(current->pi_state_cache))
368 return 0;
369
Burman Yan4668edc2006-12-06 20:38:51 -0800370 pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700371
372 if (!pi_state)
373 return -ENOMEM;
374
Ingo Molnarc87e2832006-06-27 02:54:58 -0700375 INIT_LIST_HEAD(&pi_state->list);
376 /* pi_mutex gets initialized later */
377 pi_state->owner = NULL;
378 atomic_set(&pi_state->refcount, 1);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200379 pi_state->key = FUTEX_KEY_INIT;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700380
381 current->pi_state_cache = pi_state;
382
383 return 0;
384}
385
386static struct futex_pi_state * alloc_pi_state(void)
387{
388 struct futex_pi_state *pi_state = current->pi_state_cache;
389
390 WARN_ON(!pi_state);
391 current->pi_state_cache = NULL;
392
393 return pi_state;
394}
395
396static void free_pi_state(struct futex_pi_state *pi_state)
397{
398 if (!atomic_dec_and_test(&pi_state->refcount))
399 return;
400
401 /*
402 * If pi_state->owner is NULL, the owner is most probably dying
403 * and has cleaned up the pi_state already
404 */
405 if (pi_state->owner) {
Thomas Gleixner1d615482009-11-17 14:54:03 +0100406 raw_spin_lock_irq(&pi_state->owner->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700407 list_del_init(&pi_state->list);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100408 raw_spin_unlock_irq(&pi_state->owner->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700409
410 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
411 }
412
413 if (current->pi_state_cache)
414 kfree(pi_state);
415 else {
416 /*
417 * pi_state->list is already empty.
418 * clear pi_state->owner.
419 * refcount is at 0 - put it back to 1.
420 */
421 pi_state->owner = NULL;
422 atomic_set(&pi_state->refcount, 1);
423 current->pi_state_cache = pi_state;
424 }
425}
426
427/*
428 * Look up the task based on what TID userspace gave us.
429 * We dont trust it.
430 */
431static struct task_struct * futex_find_get_task(pid_t pid)
432{
433 struct task_struct *p;
David Howellsc69e8d92008-11-14 10:39:19 +1100434 const struct cred *cred = current_cred(), *pcred;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700435
Oleg Nesterovd359b542006-09-29 02:00:55 -0700436 rcu_read_lock();
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -0700437 p = find_task_by_vpid(pid);
David Howellsc69e8d92008-11-14 10:39:19 +1100438 if (!p) {
Thomas Gleixnera06381f2007-06-23 11:48:40 +0200439 p = ERR_PTR(-ESRCH);
David Howellsc69e8d92008-11-14 10:39:19 +1100440 } else {
441 pcred = __task_cred(p);
442 if (cred->euid != pcred->euid &&
443 cred->euid != pcred->uid)
444 p = ERR_PTR(-ESRCH);
445 else
446 get_task_struct(p);
447 }
Thomas Gleixnera06381f2007-06-23 11:48:40 +0200448
Oleg Nesterovd359b542006-09-29 02:00:55 -0700449 rcu_read_unlock();
Ingo Molnarc87e2832006-06-27 02:54:58 -0700450
451 return p;
452}
453
454/*
455 * This task is holding PI mutexes at exit time => bad.
456 * Kernel cleans up PI-state, but userspace is likely hosed.
457 * (Robust-futex cleanup is separate and might save the day for userspace.)
458 */
459void exit_pi_state_list(struct task_struct *curr)
460{
Ingo Molnarc87e2832006-06-27 02:54:58 -0700461 struct list_head *next, *head = &curr->pi_state_list;
462 struct futex_pi_state *pi_state;
Ingo Molnar627371d2006-07-29 05:16:20 +0200463 struct futex_hash_bucket *hb;
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200464 union futex_key key = FUTEX_KEY_INIT;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700465
Thomas Gleixnera0c1e902008-02-23 15:23:57 -0800466 if (!futex_cmpxchg_enabled)
467 return;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700468 /*
469 * We are a ZOMBIE and nobody can enqueue itself on
470 * pi_state_list anymore, but we have to be careful
Ingo Molnar627371d2006-07-29 05:16:20 +0200471 * versus waiters unqueueing themselves:
Ingo Molnarc87e2832006-06-27 02:54:58 -0700472 */
Thomas Gleixner1d615482009-11-17 14:54:03 +0100473 raw_spin_lock_irq(&curr->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700474 while (!list_empty(head)) {
475
476 next = head->next;
477 pi_state = list_entry(next, struct futex_pi_state, list);
478 key = pi_state->key;
Ingo Molnar627371d2006-07-29 05:16:20 +0200479 hb = hash_futex(&key);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100480 raw_spin_unlock_irq(&curr->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700481
Ingo Molnarc87e2832006-06-27 02:54:58 -0700482 spin_lock(&hb->lock);
483
Thomas Gleixner1d615482009-11-17 14:54:03 +0100484 raw_spin_lock_irq(&curr->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200485 /*
486 * We dropped the pi-lock, so re-check whether this
487 * task still owns the PI-state:
488 */
Ingo Molnarc87e2832006-06-27 02:54:58 -0700489 if (head->next != next) {
490 spin_unlock(&hb->lock);
491 continue;
492 }
493
Ingo Molnarc87e2832006-06-27 02:54:58 -0700494 WARN_ON(pi_state->owner != curr);
Ingo Molnar627371d2006-07-29 05:16:20 +0200495 WARN_ON(list_empty(&pi_state->list));
496 list_del_init(&pi_state->list);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700497 pi_state->owner = NULL;
Thomas Gleixner1d615482009-11-17 14:54:03 +0100498 raw_spin_unlock_irq(&curr->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700499
500 rt_mutex_unlock(&pi_state->pi_mutex);
501
502 spin_unlock(&hb->lock);
503
Thomas Gleixner1d615482009-11-17 14:54:03 +0100504 raw_spin_lock_irq(&curr->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700505 }
Thomas Gleixner1d615482009-11-17 14:54:03 +0100506 raw_spin_unlock_irq(&curr->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700507}
508
509static int
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700510lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
511 union futex_key *key, struct futex_pi_state **ps)
Ingo Molnarc87e2832006-06-27 02:54:58 -0700512{
513 struct futex_pi_state *pi_state = NULL;
514 struct futex_q *this, *next;
Pierre Peifferec92d082007-05-09 02:35:00 -0700515 struct plist_head *head;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700516 struct task_struct *p;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700517 pid_t pid = uval & FUTEX_TID_MASK;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700518
519 head = &hb->chain;
520
Pierre Peifferec92d082007-05-09 02:35:00 -0700521 plist_for_each_entry_safe(this, next, head, list) {
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700522 if (match_futex(&this->key, key)) {
Ingo Molnarc87e2832006-06-27 02:54:58 -0700523 /*
524 * Another waiter already exists - bump up
525 * the refcount and return its pi_state:
526 */
527 pi_state = this->pi_state;
Thomas Gleixner06a9ec22006-07-10 04:44:30 -0700528 /*
529 * Userspace might have messed up non PI and PI futexes
530 */
531 if (unlikely(!pi_state))
532 return -EINVAL;
533
Ingo Molnar627371d2006-07-29 05:16:20 +0200534 WARN_ON(!atomic_read(&pi_state->refcount));
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700535 WARN_ON(pid && pi_state->owner &&
536 pi_state->owner->pid != pid);
Ingo Molnar627371d2006-07-29 05:16:20 +0200537
Ingo Molnarc87e2832006-06-27 02:54:58 -0700538 atomic_inc(&pi_state->refcount);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700539 *ps = pi_state;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700540
541 return 0;
542 }
543 }
544
545 /*
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200546 * We are the first waiter - try to look up the real owner and attach
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700547 * the new pi_state to it, but bail out when TID = 0
Ingo Molnarc87e2832006-06-27 02:54:58 -0700548 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700549 if (!pid)
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200550 return -ESRCH;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700551 p = futex_find_get_task(pid);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700552 if (IS_ERR(p))
553 return PTR_ERR(p);
554
555 /*
556 * We need to look at the task state flags to figure out,
557 * whether the task is exiting. To protect against the do_exit
558 * change of the task flags, we do this protected by
559 * p->pi_lock:
560 */
Thomas Gleixner1d615482009-11-17 14:54:03 +0100561 raw_spin_lock_irq(&p->pi_lock);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700562 if (unlikely(p->flags & PF_EXITING)) {
563 /*
564 * The task is on the way out. When PF_EXITPIDONE is
565 * set, we know that the task has finished the
566 * cleanup:
567 */
568 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
569
Thomas Gleixner1d615482009-11-17 14:54:03 +0100570 raw_spin_unlock_irq(&p->pi_lock);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700571 put_task_struct(p);
572 return ret;
573 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700574
575 pi_state = alloc_pi_state();
576
577 /*
578 * Initialize the pi_mutex in locked state and make 'p'
579 * the owner of it:
580 */
581 rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
582
583 /* Store the key for possible exit cleanups: */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700584 pi_state->key = *key;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700585
Ingo Molnar627371d2006-07-29 05:16:20 +0200586 WARN_ON(!list_empty(&pi_state->list));
Ingo Molnarc87e2832006-06-27 02:54:58 -0700587 list_add(&pi_state->list, &p->pi_state_list);
588 pi_state->owner = p;
Thomas Gleixner1d615482009-11-17 14:54:03 +0100589 raw_spin_unlock_irq(&p->pi_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700590
591 put_task_struct(p);
592
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700593 *ps = pi_state;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700594
595 return 0;
596}
597
Darren Hart1a520842009-04-03 13:39:52 -0700598/**
Darren Hartd96ee562009-09-21 22:30:22 -0700599 * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
Darren Hartbab5bc92009-04-07 23:23:50 -0700600 * @uaddr: the pi futex user address
601 * @hb: the pi futex hash bucket
602 * @key: the futex key associated with uaddr and hb
603 * @ps: the pi_state pointer where we store the result of the
604 * lookup
605 * @task: the task to perform the atomic lock work for. This will
606 * be "current" except in the case of requeue pi.
607 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
Darren Hart1a520842009-04-03 13:39:52 -0700608 *
609 * Returns:
610 * 0 - ready to wait
611 * 1 - acquired the lock
612 * <0 - error
613 *
614 * The hb->lock and futex_key refs shall be held by the caller.
615 */
616static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
617 union futex_key *key,
618 struct futex_pi_state **ps,
Darren Hartbab5bc92009-04-07 23:23:50 -0700619 struct task_struct *task, int set_waiters)
Darren Hart1a520842009-04-03 13:39:52 -0700620{
621 int lock_taken, ret, ownerdied = 0;
622 u32 uval, newval, curval;
623
624retry:
625 ret = lock_taken = 0;
626
627 /*
628 * To avoid races, we attempt to take the lock here again
629 * (by doing a 0 -> TID atomic cmpxchg), while holding all
630 * the locks. It will most likely not succeed.
631 */
632 newval = task_pid_vnr(task);
Darren Hartbab5bc92009-04-07 23:23:50 -0700633 if (set_waiters)
634 newval |= FUTEX_WAITERS;
Darren Hart1a520842009-04-03 13:39:52 -0700635
636 curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
637
638 if (unlikely(curval == -EFAULT))
639 return -EFAULT;
640
641 /*
642 * Detect deadlocks.
643 */
644 if ((unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(task))))
645 return -EDEADLK;
646
647 /*
648 * Surprise - we got the lock. Just return to userspace:
649 */
650 if (unlikely(!curval))
651 return 1;
652
653 uval = curval;
654
655 /*
656 * Set the FUTEX_WAITERS flag, so the owner will know it has someone
657 * to wake at the next unlock.
658 */
659 newval = curval | FUTEX_WAITERS;
660
661 /*
662 * There are two cases, where a futex might have no owner (the
663 * owner TID is 0): OWNER_DIED. We take over the futex in this
664 * case. We also do an unconditional take over, when the owner
665 * of the futex died.
666 *
667 * This is safe as we are protected by the hash bucket lock !
668 */
669 if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
670 /* Keep the OWNER_DIED bit */
671 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(task);
672 ownerdied = 0;
673 lock_taken = 1;
674 }
675
676 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
677
678 if (unlikely(curval == -EFAULT))
679 return -EFAULT;
680 if (unlikely(curval != uval))
681 goto retry;
682
683 /*
684 * We took the lock due to owner died take over.
685 */
686 if (unlikely(lock_taken))
687 return 1;
688
689 /*
690 * We dont have the lock. Look up the PI state (or create it if
691 * we are the first waiter):
692 */
693 ret = lookup_pi_state(uval, hb, key, ps);
694
695 if (unlikely(ret)) {
696 switch (ret) {
697 case -ESRCH:
698 /*
699 * No owner found for this futex. Check if the
700 * OWNER_DIED bit is set to figure out whether
701 * this is a robust futex or not.
702 */
703 if (get_futex_value_locked(&curval, uaddr))
704 return -EFAULT;
705
706 /*
707 * We simply start over in case of a robust
708 * futex. The code above will take the futex
709 * and return happy.
710 */
711 if (curval & FUTEX_OWNER_DIED) {
712 ownerdied = 1;
713 goto retry;
714 }
715 default:
716 break;
717 }
718 }
719
720 return ret;
721}
722
Ingo Molnarc87e2832006-06-27 02:54:58 -0700723/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 * The hash bucket lock must be held when this is called.
725 * Afterwards, the futex_q must not be accessed.
726 */
727static void wake_futex(struct futex_q *q)
728{
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +0200729 struct task_struct *p = q->task;
730
731 /*
732 * We set q->lock_ptr = NULL _before_ we wake up the task. If
733 * a non futex wake up happens on another CPU then the task
734 * might exit and p would dereference a non existing task
735 * struct. Prevent this by holding a reference on p across the
736 * wake up.
737 */
738 get_task_struct(p);
739
Pierre Peifferec92d082007-05-09 02:35:00 -0700740 plist_del(&q->list, &q->list.plist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700741 /*
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +0200742 * The waiting task can free the futex_q as soon as
743 * q->lock_ptr = NULL is written, without taking any locks. A
744 * memory barrier is required here to prevent the following
745 * store to lock_ptr from getting ahead of the plist_del.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746 */
Ralf Baechleccdea2f2006-12-06 20:40:26 -0800747 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 q->lock_ptr = NULL;
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +0200749
750 wake_up_state(p, TASK_NORMAL);
751 put_task_struct(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700752}
753
Ingo Molnarc87e2832006-06-27 02:54:58 -0700754static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
755{
756 struct task_struct *new_owner;
757 struct futex_pi_state *pi_state = this->pi_state;
758 u32 curval, newval;
759
760 if (!pi_state)
761 return -EINVAL;
762
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100763 raw_spin_lock(&pi_state->pi_mutex.wait_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700764 new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
765
766 /*
767 * This happens when we have stolen the lock and the original
768 * pending owner did not enqueue itself back on the rt_mutex.
769 * Thats not a tragedy. We know that way, that a lock waiter
770 * is on the fly. We make the futex_q waiter the pending owner.
771 */
772 if (!new_owner)
773 new_owner = this->task;
774
775 /*
776 * We pass it to the next owner. (The WAITERS bit is always
777 * kept enabled while there is PI state around. We must also
778 * preserve the owner died bit.)
779 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200780 if (!(uval & FUTEX_OWNER_DIED)) {
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700781 int ret = 0;
782
Pavel Emelyanovb4888932007-10-18 23:40:14 -0700783 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700784
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700785 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700786
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200787 if (curval == -EFAULT)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700788 ret = -EFAULT;
Thomas Gleixnercde898f2007-12-05 15:46:09 +0100789 else if (curval != uval)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700790 ret = -EINVAL;
791 if (ret) {
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100792 raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700793 return ret;
794 }
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200795 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700796
Thomas Gleixner1d615482009-11-17 14:54:03 +0100797 raw_spin_lock_irq(&pi_state->owner->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200798 WARN_ON(list_empty(&pi_state->list));
799 list_del_init(&pi_state->list);
Thomas Gleixner1d615482009-11-17 14:54:03 +0100800 raw_spin_unlock_irq(&pi_state->owner->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200801
Thomas Gleixner1d615482009-11-17 14:54:03 +0100802 raw_spin_lock_irq(&new_owner->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200803 WARN_ON(!list_empty(&pi_state->list));
Ingo Molnarc87e2832006-06-27 02:54:58 -0700804 list_add(&pi_state->list, &new_owner->pi_state_list);
805 pi_state->owner = new_owner;
Thomas Gleixner1d615482009-11-17 14:54:03 +0100806 raw_spin_unlock_irq(&new_owner->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200807
Thomas Gleixnerd209d742009-11-17 18:22:11 +0100808 raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700809 rt_mutex_unlock(&pi_state->pi_mutex);
810
811 return 0;
812}
813
814static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
815{
816 u32 oldval;
817
818 /*
819 * There is no waiter, so we unlock the futex. The owner died
820 * bit has not to be preserved here. We are the owner:
821 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700822 oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700823
824 if (oldval == -EFAULT)
825 return oldval;
826 if (oldval != uval)
827 return -EAGAIN;
828
829 return 0;
830}
831
Linus Torvalds1da177e2005-04-16 15:20:36 -0700832/*
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700833 * Express the locking dependencies for lockdep:
834 */
835static inline void
836double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
837{
838 if (hb1 <= hb2) {
839 spin_lock(&hb1->lock);
840 if (hb1 < hb2)
841 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
842 } else { /* hb1 > hb2 */
843 spin_lock(&hb2->lock);
844 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
845 }
846}
847
Darren Hart5eb3dc62009-03-12 00:55:52 -0700848static inline void
849double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
850{
Darren Hartf061d352009-03-12 15:11:18 -0700851 spin_unlock(&hb1->lock);
Ingo Molnar88f502f2009-03-13 10:32:07 +0100852 if (hb1 != hb2)
853 spin_unlock(&hb2->lock);
Darren Hart5eb3dc62009-03-12 00:55:52 -0700854}
855
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700856/*
Darren Hartb2d09942009-03-12 00:55:37 -0700857 * Wake up waiters matching bitset queued on this futex (uaddr).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200859static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860{
Ingo Molnare2970f22006-06-27 02:54:47 -0700861 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700862 struct futex_q *this, *next;
Pierre Peifferec92d082007-05-09 02:35:00 -0700863 struct plist_head *head;
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200864 union futex_key key = FUTEX_KEY_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865 int ret;
866
Thomas Gleixnercd689982008-02-01 17:45:14 +0100867 if (!bitset)
868 return -EINVAL;
869
Thomas Gleixner64d13042009-05-18 21:20:10 +0200870 ret = get_futex_key(uaddr, fshared, &key, VERIFY_READ);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 if (unlikely(ret != 0))
872 goto out;
873
Ingo Molnare2970f22006-06-27 02:54:47 -0700874 hb = hash_futex(&key);
875 spin_lock(&hb->lock);
876 head = &hb->chain;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877
Pierre Peifferec92d082007-05-09 02:35:00 -0700878 plist_for_each_entry_safe(this, next, head, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 if (match_futex (&this->key, &key)) {
Darren Hart52400ba2009-04-03 13:40:49 -0700880 if (this->pi_state || this->rt_waiter) {
Ingo Molnared6f7b12006-07-01 04:35:46 -0700881 ret = -EINVAL;
882 break;
883 }
Thomas Gleixnercd689982008-02-01 17:45:14 +0100884
885 /* Check if one of the bits is set in both bitsets */
886 if (!(this->bitset & bitset))
887 continue;
888
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 wake_futex(this);
890 if (++ret >= nr_wake)
891 break;
892 }
893 }
894
Ingo Molnare2970f22006-06-27 02:54:47 -0700895 spin_unlock(&hb->lock);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200896 put_futex_key(fshared, &key);
Darren Hart42d35d42008-12-29 15:49:53 -0800897out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 return ret;
899}
900
901/*
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700902 * Wake up all waiters hashed on the physical page that is mapped
903 * to this virtual address:
904 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700905static int
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200906futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
Ingo Molnare2970f22006-06-27 02:54:47 -0700907 int nr_wake, int nr_wake2, int op)
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700908{
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200909 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
Ingo Molnare2970f22006-06-27 02:54:47 -0700910 struct futex_hash_bucket *hb1, *hb2;
Pierre Peifferec92d082007-05-09 02:35:00 -0700911 struct plist_head *head;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700912 struct futex_q *this, *next;
Darren Harte4dc5b72009-03-12 00:56:13 -0700913 int ret, op_ret;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700914
Darren Harte4dc5b72009-03-12 00:56:13 -0700915retry:
Thomas Gleixner64d13042009-05-18 21:20:10 +0200916 ret = get_futex_key(uaddr1, fshared, &key1, VERIFY_READ);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700917 if (unlikely(ret != 0))
918 goto out;
Thomas Gleixner64d13042009-05-18 21:20:10 +0200919 ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_WRITE);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700920 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -0800921 goto out_put_key1;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700922
Ingo Molnare2970f22006-06-27 02:54:47 -0700923 hb1 = hash_futex(&key1);
924 hb2 = hash_futex(&key2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700925
Darren Harte4dc5b72009-03-12 00:56:13 -0700926retry_private:
Thomas Gleixnereaaea802009-10-04 09:34:17 +0200927 double_lock_hb(hb1, hb2);
Ingo Molnare2970f22006-06-27 02:54:47 -0700928 op_ret = futex_atomic_op_inuser(op, uaddr2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700929 if (unlikely(op_ret < 0)) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700930
Darren Hart5eb3dc62009-03-12 00:55:52 -0700931 double_unlock_hb(hb1, hb2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700932
David Howells7ee1dd32006-01-06 00:11:44 -0800933#ifndef CONFIG_MMU
Ingo Molnare2970f22006-06-27 02:54:47 -0700934 /*
935 * we don't get EFAULT from MMU faults if we don't have an MMU,
936 * but we might get them from range checking
937 */
David Howells7ee1dd32006-01-06 00:11:44 -0800938 ret = op_ret;
Darren Hart42d35d42008-12-29 15:49:53 -0800939 goto out_put_keys;
David Howells7ee1dd32006-01-06 00:11:44 -0800940#endif
941
David Gibson796f8d92005-11-07 00:59:33 -0800942 if (unlikely(op_ret != -EFAULT)) {
943 ret = op_ret;
Darren Hart42d35d42008-12-29 15:49:53 -0800944 goto out_put_keys;
David Gibson796f8d92005-11-07 00:59:33 -0800945 }
946
Thomas Gleixnerd0725992009-06-11 23:15:43 +0200947 ret = fault_in_user_writeable(uaddr2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700948 if (ret)
Darren Hartde87fcc2009-03-12 00:55:46 -0700949 goto out_put_keys;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700950
Darren Harte4dc5b72009-03-12 00:56:13 -0700951 if (!fshared)
952 goto retry_private;
953
Darren Hartde87fcc2009-03-12 00:55:46 -0700954 put_futex_key(fshared, &key2);
955 put_futex_key(fshared, &key1);
Darren Harte4dc5b72009-03-12 00:56:13 -0700956 goto retry;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700957 }
958
Ingo Molnare2970f22006-06-27 02:54:47 -0700959 head = &hb1->chain;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700960
Pierre Peifferec92d082007-05-09 02:35:00 -0700961 plist_for_each_entry_safe(this, next, head, list) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700962 if (match_futex (&this->key, &key1)) {
963 wake_futex(this);
964 if (++ret >= nr_wake)
965 break;
966 }
967 }
968
969 if (op_ret > 0) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700970 head = &hb2->chain;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700971
972 op_ret = 0;
Pierre Peifferec92d082007-05-09 02:35:00 -0700973 plist_for_each_entry_safe(this, next, head, list) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700974 if (match_futex (&this->key, &key2)) {
975 wake_futex(this);
976 if (++op_ret >= nr_wake2)
977 break;
978 }
979 }
980 ret += op_ret;
981 }
982
Darren Hart5eb3dc62009-03-12 00:55:52 -0700983 double_unlock_hb(hb1, hb2);
Darren Hart42d35d42008-12-29 15:49:53 -0800984out_put_keys:
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200985 put_futex_key(fshared, &key2);
Darren Hart42d35d42008-12-29 15:49:53 -0800986out_put_key1:
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200987 put_futex_key(fshared, &key1);
Darren Hart42d35d42008-12-29 15:49:53 -0800988out:
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700989 return ret;
990}
991
Darren Hart9121e472009-04-03 13:40:31 -0700992/**
993 * requeue_futex() - Requeue a futex_q from one hb to another
994 * @q: the futex_q to requeue
995 * @hb1: the source hash_bucket
996 * @hb2: the target hash_bucket
997 * @key2: the new key for the requeued futex_q
998 */
999static inline
1000void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
1001 struct futex_hash_bucket *hb2, union futex_key *key2)
1002{
1003
1004 /*
1005 * If key1 and key2 hash to the same bucket, no need to
1006 * requeue.
1007 */
1008 if (likely(&hb1->chain != &hb2->chain)) {
1009 plist_del(&q->list, &hb1->chain);
1010 plist_add(&q->list, &hb2->chain);
1011 q->lock_ptr = &hb2->lock;
1012#ifdef CONFIG_DEBUG_PI_LIST
Thomas Gleixnera2672452009-11-17 14:46:14 +01001013 q->list.plist.spinlock = &hb2->lock;
Darren Hart9121e472009-04-03 13:40:31 -07001014#endif
1015 }
1016 get_futex_key_refs(key2);
1017 q->key = *key2;
1018}
1019
Darren Hart52400ba2009-04-03 13:40:49 -07001020/**
1021 * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue
Darren Hartd96ee562009-09-21 22:30:22 -07001022 * @q: the futex_q
1023 * @key: the key of the requeue target futex
1024 * @hb: the hash_bucket of the requeue target futex
Darren Hart52400ba2009-04-03 13:40:49 -07001025 *
1026 * During futex_requeue, with requeue_pi=1, it is possible to acquire the
1027 * target futex if it is uncontended or via a lock steal. Set the futex_q key
1028 * to the requeue target futex so the waiter can detect the wakeup on the right
1029 * futex, but remove it from the hb and NULL the rt_waiter so it can detect
Darren Hartbeda2c72009-08-09 15:34:39 -07001030 * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock
1031 * to protect access to the pi_state to fixup the owner later. Must be called
1032 * with both q->lock_ptr and hb->lock held.
Darren Hart52400ba2009-04-03 13:40:49 -07001033 */
1034static inline
Darren Hartbeda2c72009-08-09 15:34:39 -07001035void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
1036 struct futex_hash_bucket *hb)
Darren Hart52400ba2009-04-03 13:40:49 -07001037{
Darren Hart52400ba2009-04-03 13:40:49 -07001038 get_futex_key_refs(key);
1039 q->key = *key;
1040
1041 WARN_ON(plist_node_empty(&q->list));
1042 plist_del(&q->list, &q->list.plist);
1043
1044 WARN_ON(!q->rt_waiter);
1045 q->rt_waiter = NULL;
1046
Darren Hartbeda2c72009-08-09 15:34:39 -07001047 q->lock_ptr = &hb->lock;
1048#ifdef CONFIG_DEBUG_PI_LIST
Thomas Gleixnera2672452009-11-17 14:46:14 +01001049 q->list.plist.spinlock = &hb->lock;
Darren Hartbeda2c72009-08-09 15:34:39 -07001050#endif
1051
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +02001052 wake_up_state(q->task, TASK_NORMAL);
Darren Hart52400ba2009-04-03 13:40:49 -07001053}
1054
1055/**
1056 * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
Darren Hartbab5bc92009-04-07 23:23:50 -07001057 * @pifutex: the user address of the to futex
1058 * @hb1: the from futex hash bucket, must be locked by the caller
1059 * @hb2: the to futex hash bucket, must be locked by the caller
1060 * @key1: the from futex key
1061 * @key2: the to futex key
1062 * @ps: address to store the pi_state pointer
1063 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
Darren Hart52400ba2009-04-03 13:40:49 -07001064 *
1065 * Try and get the lock on behalf of the top waiter if we can do it atomically.
Darren Hartbab5bc92009-04-07 23:23:50 -07001066 * Wake the top waiter if we succeed. If the caller specified set_waiters,
1067 * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
1068 * hb1 and hb2 must be held by the caller.
Darren Hart52400ba2009-04-03 13:40:49 -07001069 *
1070 * Returns:
1071 * 0 - failed to acquire the lock atomicly
1072 * 1 - acquired the lock
1073 * <0 - error
1074 */
1075static int futex_proxy_trylock_atomic(u32 __user *pifutex,
1076 struct futex_hash_bucket *hb1,
1077 struct futex_hash_bucket *hb2,
1078 union futex_key *key1, union futex_key *key2,
Darren Hartbab5bc92009-04-07 23:23:50 -07001079 struct futex_pi_state **ps, int set_waiters)
Darren Hart52400ba2009-04-03 13:40:49 -07001080{
Darren Hartbab5bc92009-04-07 23:23:50 -07001081 struct futex_q *top_waiter = NULL;
Darren Hart52400ba2009-04-03 13:40:49 -07001082 u32 curval;
1083 int ret;
1084
1085 if (get_futex_value_locked(&curval, pifutex))
1086 return -EFAULT;
1087
Darren Hartbab5bc92009-04-07 23:23:50 -07001088 /*
1089 * Find the top_waiter and determine if there are additional waiters.
1090 * If the caller intends to requeue more than 1 waiter to pifutex,
1091 * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
1092 * as we have means to handle the possible fault. If not, don't set
1093 * the bit unecessarily as it will force the subsequent unlock to enter
1094 * the kernel.
1095 */
Darren Hart52400ba2009-04-03 13:40:49 -07001096 top_waiter = futex_top_waiter(hb1, key1);
1097
1098 /* There are no waiters, nothing for us to do. */
1099 if (!top_waiter)
1100 return 0;
1101
Darren Hart84bc4af2009-08-13 17:36:53 -07001102 /* Ensure we requeue to the expected futex. */
1103 if (!match_futex(top_waiter->requeue_pi_key, key2))
1104 return -EINVAL;
1105
Darren Hart52400ba2009-04-03 13:40:49 -07001106 /*
Darren Hartbab5bc92009-04-07 23:23:50 -07001107 * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in
1108 * the contended case or if set_waiters is 1. The pi_state is returned
1109 * in ps in contended cases.
Darren Hart52400ba2009-04-03 13:40:49 -07001110 */
Darren Hartbab5bc92009-04-07 23:23:50 -07001111 ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
1112 set_waiters);
Darren Hart52400ba2009-04-03 13:40:49 -07001113 if (ret == 1)
Darren Hartbeda2c72009-08-09 15:34:39 -07001114 requeue_pi_wake_futex(top_waiter, key2, hb2);
Darren Hart52400ba2009-04-03 13:40:49 -07001115
1116 return ret;
1117}
1118
1119/**
1120 * futex_requeue() - Requeue waiters from uaddr1 to uaddr2
1121 * uaddr1: source futex user address
1122 * uaddr2: target futex user address
1123 * nr_wake: number of waiters to wake (must be 1 for requeue_pi)
1124 * nr_requeue: number of waiters to requeue (0-INT_MAX)
1125 * requeue_pi: if we are attempting to requeue from a non-pi futex to a
1126 * pi futex (pi to pi requeue is not supported)
1127 *
1128 * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
1129 * uaddr2 atomically on behalf of the top waiter.
1130 *
1131 * Returns:
1132 * >=0 - on success, the number of tasks requeued or woken
1133 * <0 - on error
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001135static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
Darren Hart52400ba2009-04-03 13:40:49 -07001136 int nr_wake, int nr_requeue, u32 *cmpval,
1137 int requeue_pi)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001138{
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001139 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
Darren Hart52400ba2009-04-03 13:40:49 -07001140 int drop_count = 0, task_count = 0, ret;
1141 struct futex_pi_state *pi_state = NULL;
Ingo Molnare2970f22006-06-27 02:54:47 -07001142 struct futex_hash_bucket *hb1, *hb2;
Pierre Peifferec92d082007-05-09 02:35:00 -07001143 struct plist_head *head1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001144 struct futex_q *this, *next;
Darren Hart52400ba2009-04-03 13:40:49 -07001145 u32 curval2;
1146
1147 if (requeue_pi) {
1148 /*
1149 * requeue_pi requires a pi_state, try to allocate it now
1150 * without any locks in case it fails.
1151 */
1152 if (refill_pi_state_cache())
1153 return -ENOMEM;
1154 /*
1155 * requeue_pi must wake as many tasks as it can, up to nr_wake
1156 * + nr_requeue, since it acquires the rt_mutex prior to
1157 * returning to userspace, so as to not leave the rt_mutex with
1158 * waiters and no owner. However, second and third wake-ups
1159 * cannot be predicted as they involve race conditions with the
1160 * first wake and a fault while looking up the pi_state. Both
1161 * pthread_cond_signal() and pthread_cond_broadcast() should
1162 * use nr_wake=1.
1163 */
1164 if (nr_wake != 1)
1165 return -EINVAL;
1166 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167
Darren Hart42d35d42008-12-29 15:49:53 -08001168retry:
Darren Hart52400ba2009-04-03 13:40:49 -07001169 if (pi_state != NULL) {
1170 /*
1171 * We will have to lookup the pi_state again, so free this one
1172 * to keep the accounting correct.
1173 */
1174 free_pi_state(pi_state);
1175 pi_state = NULL;
1176 }
1177
Thomas Gleixner64d13042009-05-18 21:20:10 +02001178 ret = get_futex_key(uaddr1, fshared, &key1, VERIFY_READ);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179 if (unlikely(ret != 0))
1180 goto out;
Thomas Gleixner521c1802009-05-20 09:02:28 +02001181 ret = get_futex_key(uaddr2, fshared, &key2,
1182 requeue_pi ? VERIFY_WRITE : VERIFY_READ);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -08001184 goto out_put_key1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185
Ingo Molnare2970f22006-06-27 02:54:47 -07001186 hb1 = hash_futex(&key1);
1187 hb2 = hash_futex(&key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188
Darren Harte4dc5b72009-03-12 00:56:13 -07001189retry_private:
Ingo Molnar8b8f3192006-07-03 00:25:05 -07001190 double_lock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191
Ingo Molnare2970f22006-06-27 02:54:47 -07001192 if (likely(cmpval != NULL)) {
1193 u32 curval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194
Ingo Molnare2970f22006-06-27 02:54:47 -07001195 ret = get_futex_value_locked(&curval, uaddr1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196
1197 if (unlikely(ret)) {
Darren Hart5eb3dc62009-03-12 00:55:52 -07001198 double_unlock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199
Darren Harte4dc5b72009-03-12 00:56:13 -07001200 ret = get_user(curval, uaddr1);
1201 if (ret)
1202 goto out_put_keys;
1203
1204 if (!fshared)
1205 goto retry_private;
1206
Darren Hartde87fcc2009-03-12 00:55:46 -07001207 put_futex_key(fshared, &key2);
1208 put_futex_key(fshared, &key1);
Darren Harte4dc5b72009-03-12 00:56:13 -07001209 goto retry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210 }
Ingo Molnare2970f22006-06-27 02:54:47 -07001211 if (curval != *cmpval) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001212 ret = -EAGAIN;
1213 goto out_unlock;
1214 }
1215 }
1216
Darren Hart52400ba2009-04-03 13:40:49 -07001217 if (requeue_pi && (task_count - nr_wake < nr_requeue)) {
Darren Hartbab5bc92009-04-07 23:23:50 -07001218 /*
1219 * Attempt to acquire uaddr2 and wake the top waiter. If we
1220 * intend to requeue waiters, force setting the FUTEX_WAITERS
1221 * bit. We force this here where we are able to easily handle
1222 * faults rather in the requeue loop below.
1223 */
Darren Hart52400ba2009-04-03 13:40:49 -07001224 ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1,
Darren Hartbab5bc92009-04-07 23:23:50 -07001225 &key2, &pi_state, nr_requeue);
Darren Hart52400ba2009-04-03 13:40:49 -07001226
1227 /*
1228 * At this point the top_waiter has either taken uaddr2 or is
1229 * waiting on it. If the former, then the pi_state will not
1230 * exist yet, look it up one more time to ensure we have a
1231 * reference to it.
1232 */
1233 if (ret == 1) {
1234 WARN_ON(pi_state);
Darren Hart89061d32009-10-15 15:30:48 -07001235 drop_count++;
Darren Hart52400ba2009-04-03 13:40:49 -07001236 task_count++;
1237 ret = get_futex_value_locked(&curval2, uaddr2);
1238 if (!ret)
1239 ret = lookup_pi_state(curval2, hb2, &key2,
1240 &pi_state);
1241 }
1242
1243 switch (ret) {
1244 case 0:
1245 break;
1246 case -EFAULT:
1247 double_unlock_hb(hb1, hb2);
1248 put_futex_key(fshared, &key2);
1249 put_futex_key(fshared, &key1);
Thomas Gleixnerd0725992009-06-11 23:15:43 +02001250 ret = fault_in_user_writeable(uaddr2);
Darren Hart52400ba2009-04-03 13:40:49 -07001251 if (!ret)
1252 goto retry;
1253 goto out;
1254 case -EAGAIN:
1255 /* The owner was exiting, try again. */
1256 double_unlock_hb(hb1, hb2);
1257 put_futex_key(fshared, &key2);
1258 put_futex_key(fshared, &key1);
1259 cond_resched();
1260 goto retry;
1261 default:
1262 goto out_unlock;
1263 }
1264 }
1265
Ingo Molnare2970f22006-06-27 02:54:47 -07001266 head1 = &hb1->chain;
Pierre Peifferec92d082007-05-09 02:35:00 -07001267 plist_for_each_entry_safe(this, next, head1, list) {
Darren Hart52400ba2009-04-03 13:40:49 -07001268 if (task_count - nr_wake >= nr_requeue)
1269 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001270
Darren Hart52400ba2009-04-03 13:40:49 -07001271 if (!match_futex(&this->key, &key1))
1272 continue;
1273
Darren Hart392741e2009-08-07 15:20:48 -07001274 /*
1275 * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
1276 * be paired with each other and no other futex ops.
1277 */
1278 if ((requeue_pi && !this->rt_waiter) ||
1279 (!requeue_pi && this->rt_waiter)) {
1280 ret = -EINVAL;
1281 break;
1282 }
Darren Hart52400ba2009-04-03 13:40:49 -07001283
1284 /*
1285 * Wake nr_wake waiters. For requeue_pi, if we acquired the
1286 * lock, we already woke the top_waiter. If not, it will be
1287 * woken by futex_unlock_pi().
1288 */
1289 if (++task_count <= nr_wake && !requeue_pi) {
1290 wake_futex(this);
1291 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 }
Darren Hart52400ba2009-04-03 13:40:49 -07001293
Darren Hart84bc4af2009-08-13 17:36:53 -07001294 /* Ensure we requeue to the expected futex for requeue_pi. */
1295 if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) {
1296 ret = -EINVAL;
1297 break;
1298 }
1299
Darren Hart52400ba2009-04-03 13:40:49 -07001300 /*
1301 * Requeue nr_requeue waiters and possibly one more in the case
1302 * of requeue_pi if we couldn't acquire the lock atomically.
1303 */
1304 if (requeue_pi) {
1305 /* Prepare the waiter to take the rt_mutex. */
1306 atomic_inc(&pi_state->refcount);
1307 this->pi_state = pi_state;
1308 ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
1309 this->rt_waiter,
1310 this->task, 1);
1311 if (ret == 1) {
1312 /* We got the lock. */
Darren Hartbeda2c72009-08-09 15:34:39 -07001313 requeue_pi_wake_futex(this, &key2, hb2);
Darren Hart89061d32009-10-15 15:30:48 -07001314 drop_count++;
Darren Hart52400ba2009-04-03 13:40:49 -07001315 continue;
1316 } else if (ret) {
1317 /* -EDEADLK */
1318 this->pi_state = NULL;
1319 free_pi_state(pi_state);
1320 goto out_unlock;
1321 }
1322 }
1323 requeue_futex(this, hb1, hb2, &key2);
1324 drop_count++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325 }
1326
1327out_unlock:
Darren Hart5eb3dc62009-03-12 00:55:52 -07001328 double_unlock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329
Darren Hartcd84a422009-04-02 14:19:38 -07001330 /*
1331 * drop_futex_key_refs() must be called outside the spinlocks. During
1332 * the requeue we moved futex_q's from the hash bucket at key1 to the
1333 * one at key2 and updated their key pointer. We no longer need to
1334 * hold the references to key1.
1335 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 while (--drop_count >= 0)
Rusty Russell9adef582007-05-08 00:26:42 -07001337 drop_futex_key_refs(&key1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338
Darren Hart42d35d42008-12-29 15:49:53 -08001339out_put_keys:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001340 put_futex_key(fshared, &key2);
Darren Hart42d35d42008-12-29 15:49:53 -08001341out_put_key1:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001342 put_futex_key(fshared, &key1);
Darren Hart42d35d42008-12-29 15:49:53 -08001343out:
Darren Hart52400ba2009-04-03 13:40:49 -07001344 if (pi_state != NULL)
1345 free_pi_state(pi_state);
1346 return ret ? ret : task_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347}
1348
1349/* The key must be already stored in q->key. */
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001350static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351{
Ingo Molnare2970f22006-06-27 02:54:47 -07001352 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353
Rusty Russell9adef582007-05-08 00:26:42 -07001354 get_futex_key_refs(&q->key);
Ingo Molnare2970f22006-06-27 02:54:47 -07001355 hb = hash_futex(&q->key);
1356 q->lock_ptr = &hb->lock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357
Ingo Molnare2970f22006-06-27 02:54:47 -07001358 spin_lock(&hb->lock);
1359 return hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360}
1361
Darren Hartd40d65c2009-09-21 22:30:15 -07001362static inline void
1363queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
1364{
1365 spin_unlock(&hb->lock);
1366 drop_futex_key_refs(&q->key);
1367}
1368
1369/**
1370 * queue_me() - Enqueue the futex_q on the futex_hash_bucket
1371 * @q: The futex_q to enqueue
1372 * @hb: The destination hash bucket
1373 *
1374 * The hb->lock must be held by the caller, and is released here. A call to
1375 * queue_me() is typically paired with exactly one call to unqueue_me(). The
1376 * exceptions involve the PI related operations, which may use unqueue_me_pi()
1377 * or nothing if the unqueue is done as part of the wake process and the unqueue
1378 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
1379 * an example).
1380 */
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001381static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382{
Pierre Peifferec92d082007-05-09 02:35:00 -07001383 int prio;
1384
1385 /*
1386 * The priority used to register this element is
1387 * - either the real thread-priority for the real-time threads
1388 * (i.e. threads with a priority lower than MAX_RT_PRIO)
1389 * - or MAX_RT_PRIO for non-RT threads.
1390 * Thus, all RT-threads are woken first in priority order, and
1391 * the others are woken last, in FIFO order.
1392 */
1393 prio = min(current->normal_prio, MAX_RT_PRIO);
1394
1395 plist_node_init(&q->list, prio);
1396#ifdef CONFIG_DEBUG_PI_LIST
Thomas Gleixnera2672452009-11-17 14:46:14 +01001397 q->list.plist.spinlock = &hb->lock;
Pierre Peifferec92d082007-05-09 02:35:00 -07001398#endif
1399 plist_add(&q->list, &hb->chain);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001400 q->task = current;
Ingo Molnare2970f22006-06-27 02:54:47 -07001401 spin_unlock(&hb->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001402}
1403
Darren Hartd40d65c2009-09-21 22:30:15 -07001404/**
1405 * unqueue_me() - Remove the futex_q from its futex_hash_bucket
1406 * @q: The futex_q to unqueue
1407 *
1408 * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must
1409 * be paired with exactly one earlier call to queue_me().
1410 *
1411 * Returns:
1412 * 1 - if the futex_q was still queued (and we removed unqueued it)
1413 * 0 - if the futex_q was already removed by the waking thread
Linus Torvalds1da177e2005-04-16 15:20:36 -07001414 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001415static int unqueue_me(struct futex_q *q)
1416{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417 spinlock_t *lock_ptr;
Ingo Molnare2970f22006-06-27 02:54:47 -07001418 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001419
1420 /* In the common case we don't take the spinlock, which is nice. */
Darren Hart42d35d42008-12-29 15:49:53 -08001421retry:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422 lock_ptr = q->lock_ptr;
Christian Borntraegere91467e2006-08-05 12:13:52 -07001423 barrier();
Stephen Hemmingerc80544d2007-10-18 03:07:05 -07001424 if (lock_ptr != NULL) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425 spin_lock(lock_ptr);
1426 /*
1427 * q->lock_ptr can change between reading it and
1428 * spin_lock(), causing us to take the wrong lock. This
1429 * corrects the race condition.
1430 *
1431 * Reasoning goes like this: if we have the wrong lock,
1432 * q->lock_ptr must have changed (maybe several times)
1433 * between reading it and the spin_lock(). It can
1434 * change again after the spin_lock() but only if it was
1435 * already changed before the spin_lock(). It cannot,
1436 * however, change back to the original value. Therefore
1437 * we can detect whether we acquired the correct lock.
1438 */
1439 if (unlikely(lock_ptr != q->lock_ptr)) {
1440 spin_unlock(lock_ptr);
1441 goto retry;
1442 }
Pierre Peifferec92d082007-05-09 02:35:00 -07001443 WARN_ON(plist_node_empty(&q->list));
1444 plist_del(&q->list, &q->list.plist);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001445
1446 BUG_ON(q->pi_state);
1447
Linus Torvalds1da177e2005-04-16 15:20:36 -07001448 spin_unlock(lock_ptr);
1449 ret = 1;
1450 }
1451
Rusty Russell9adef582007-05-08 00:26:42 -07001452 drop_futex_key_refs(&q->key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001453 return ret;
1454}
1455
Ingo Molnarc87e2832006-06-27 02:54:58 -07001456/*
1457 * PI futexes can not be requeued and must remove themself from the
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001458 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1459 * and dropped here.
Ingo Molnarc87e2832006-06-27 02:54:58 -07001460 */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001461static void unqueue_me_pi(struct futex_q *q)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001462{
Pierre Peifferec92d082007-05-09 02:35:00 -07001463 WARN_ON(plist_node_empty(&q->list));
1464 plist_del(&q->list, &q->list.plist);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001465
1466 BUG_ON(!q->pi_state);
1467 free_pi_state(q->pi_state);
1468 q->pi_state = NULL;
1469
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001470 spin_unlock(q->lock_ptr);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001471
Rusty Russell9adef582007-05-08 00:26:42 -07001472 drop_futex_key_refs(&q->key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001473}
1474
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001475/*
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001476 * Fixup the pi_state owner with the new owner.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001477 *
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001478 * Must be called with hash bucket lock held and mm->sem held for non
1479 * private futexes.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001480 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001481static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001482 struct task_struct *newowner, int fshared)
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001483{
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001484 u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001485 struct futex_pi_state *pi_state = q->pi_state;
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001486 struct task_struct *oldowner = pi_state->owner;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001487 u32 uval, curval, newval;
Darren Harte4dc5b72009-03-12 00:56:13 -07001488 int ret;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001489
1490 /* Owner died? */
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001491 if (!pi_state->owner)
1492 newtid |= FUTEX_OWNER_DIED;
1493
1494 /*
1495 * We are here either because we stole the rtmutex from the
1496 * pending owner or we are the pending owner which failed to
1497 * get the rtmutex. We have to replace the pending owner TID
1498 * in the user space variable. This must be atomic as we have
1499 * to preserve the owner died bit here.
1500 *
Darren Hartb2d09942009-03-12 00:55:37 -07001501 * Note: We write the user space value _before_ changing the pi_state
1502 * because we can fault here. Imagine swapped out pages or a fork
1503 * that marked all the anonymous memory readonly for cow.
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001504 *
1505 * Modifying pi_state _before_ the user space value would
1506 * leave the pi_state in an inconsistent state when we fault
1507 * here, because we need to drop the hash bucket lock to
1508 * handle the fault. This might be observed in the PID check
1509 * in lookup_pi_state.
1510 */
1511retry:
1512 if (get_futex_value_locked(&uval, uaddr))
1513 goto handle_fault;
1514
1515 while (1) {
1516 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1517
1518 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1519
1520 if (curval == -EFAULT)
1521 goto handle_fault;
1522 if (curval == uval)
1523 break;
1524 uval = curval;
1525 }
1526
1527 /*
1528 * We fixed up user space. Now we need to fix the pi_state
1529 * itself.
1530 */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001531 if (pi_state->owner != NULL) {
Thomas Gleixner1d615482009-11-17 14:54:03 +01001532 raw_spin_lock_irq(&pi_state->owner->pi_lock);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001533 WARN_ON(list_empty(&pi_state->list));
1534 list_del_init(&pi_state->list);
Thomas Gleixner1d615482009-11-17 14:54:03 +01001535 raw_spin_unlock_irq(&pi_state->owner->pi_lock);
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001536 }
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001537
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001538 pi_state->owner = newowner;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001539
Thomas Gleixner1d615482009-11-17 14:54:03 +01001540 raw_spin_lock_irq(&newowner->pi_lock);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001541 WARN_ON(!list_empty(&pi_state->list));
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001542 list_add(&pi_state->list, &newowner->pi_state_list);
Thomas Gleixner1d615482009-11-17 14:54:03 +01001543 raw_spin_unlock_irq(&newowner->pi_lock);
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001544 return 0;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001545
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001546 /*
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001547 * To handle the page fault we need to drop the hash bucket
1548 * lock here. That gives the other task (either the pending
1549 * owner itself or the task which stole the rtmutex) the
1550 * chance to try the fixup of the pi_state. So once we are
1551 * back from handling the fault we need to check the pi_state
1552 * after reacquiring the hash bucket lock and before trying to
1553 * do another fixup. When the fixup has been done already we
1554 * simply return.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001555 */
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001556handle_fault:
1557 spin_unlock(q->lock_ptr);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001558
Thomas Gleixnerd0725992009-06-11 23:15:43 +02001559 ret = fault_in_user_writeable(uaddr);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001560
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001561 spin_lock(q->lock_ptr);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001562
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001563 /*
1564 * Check if someone else fixed it for us:
1565 */
1566 if (pi_state->owner != oldowner)
1567 return 0;
1568
1569 if (ret)
1570 return ret;
1571
1572 goto retry;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001573}
1574
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001575/*
1576 * In case we must use restart_block to restart a futex_wait,
Steven Rostedtce6bd422007-12-05 15:46:09 +01001577 * we encode in the 'flags' shared capability
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001578 */
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001579#define FLAGS_SHARED 0x01
1580#define FLAGS_CLOCKRT 0x02
Darren Harta72188d2009-04-03 13:40:22 -07001581#define FLAGS_HAS_TIMEOUT 0x04
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001582
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001583static long futex_wait_restart(struct restart_block *restart);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001584
Darren Hartca5f9522009-04-03 13:39:33 -07001585/**
Darren Hartdd973992009-04-03 13:40:02 -07001586 * fixup_owner() - Post lock pi_state and corner case management
1587 * @uaddr: user address of the futex
1588 * @fshared: whether the futex is shared (1) or not (0)
1589 * @q: futex_q (contains pi_state and access to the rt_mutex)
1590 * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
1591 *
1592 * After attempting to lock an rt_mutex, this function is called to cleanup
1593 * the pi_state owner as well as handle race conditions that may allow us to
1594 * acquire the lock. Must be called with the hb lock held.
1595 *
1596 * Returns:
1597 * 1 - success, lock taken
1598 * 0 - success, lock not taken
1599 * <0 - on error (-EFAULT)
1600 */
1601static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
1602 int locked)
1603{
1604 struct task_struct *owner;
1605 int ret = 0;
1606
1607 if (locked) {
1608 /*
1609 * Got the lock. We might not be the anticipated owner if we
1610 * did a lock-steal - fix up the PI-state in that case:
1611 */
1612 if (q->pi_state->owner != current)
1613 ret = fixup_pi_state_owner(uaddr, q, current, fshared);
1614 goto out;
1615 }
1616
1617 /*
1618 * Catch the rare case, where the lock was released when we were on the
1619 * way back before we locked the hash bucket.
1620 */
1621 if (q->pi_state->owner == current) {
1622 /*
1623 * Try to get the rt_mutex now. This might fail as some other
1624 * task acquired the rt_mutex after we removed ourself from the
1625 * rt_mutex waiters list.
1626 */
1627 if (rt_mutex_trylock(&q->pi_state->pi_mutex)) {
1628 locked = 1;
1629 goto out;
1630 }
1631
1632 /*
1633 * pi_state is incorrect, some other task did a lock steal and
1634 * we returned due to timeout or signal without taking the
1635 * rt_mutex. Too late. We can access the rt_mutex_owner without
1636 * locking, as the other task is now blocked on the hash bucket
1637 * lock. Fix the state up.
1638 */
1639 owner = rt_mutex_owner(&q->pi_state->pi_mutex);
1640 ret = fixup_pi_state_owner(uaddr, q, owner, fshared);
1641 goto out;
1642 }
1643
1644 /*
1645 * Paranoia check. If we did not take the lock, then we should not be
1646 * the owner, nor the pending owner, of the rt_mutex.
1647 */
1648 if (rt_mutex_owner(&q->pi_state->pi_mutex) == current)
1649 printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p "
1650 "pi-state %p\n", ret,
1651 q->pi_state->pi_mutex.owner,
1652 q->pi_state->owner);
1653
1654out:
1655 return ret ? ret : locked;
1656}
1657
1658/**
Darren Hartca5f9522009-04-03 13:39:33 -07001659 * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
1660 * @hb: the futex hash bucket, must be locked by the caller
1661 * @q: the futex_q to queue up on
1662 * @timeout: the prepared hrtimer_sleeper, or null for no timeout
Darren Hartca5f9522009-04-03 13:39:33 -07001663 */
1664static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +02001665 struct hrtimer_sleeper *timeout)
Darren Hartca5f9522009-04-03 13:39:33 -07001666{
Darren Hart9beba3c2009-09-24 11:54:47 -07001667 /*
1668 * The task state is guaranteed to be set before another task can
1669 * wake it. set_current_state() is implemented using set_mb() and
1670 * queue_me() calls spin_unlock() upon completion, both serializing
1671 * access to the hash list and forcing another memory barrier.
1672 */
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +02001673 set_current_state(TASK_INTERRUPTIBLE);
Darren Hart0729e192009-09-21 22:30:38 -07001674 queue_me(q, hb);
Darren Hartca5f9522009-04-03 13:39:33 -07001675
1676 /* Arm the timer */
1677 if (timeout) {
1678 hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
1679 if (!hrtimer_active(&timeout->timer))
1680 timeout->task = NULL;
1681 }
1682
1683 /*
Darren Hart0729e192009-09-21 22:30:38 -07001684 * If we have been removed from the hash list, then another task
1685 * has tried to wake us, and we can skip the call to schedule().
Darren Hartca5f9522009-04-03 13:39:33 -07001686 */
1687 if (likely(!plist_node_empty(&q->list))) {
1688 /*
1689 * If the timer has already expired, current will already be
1690 * flagged for rescheduling. Only call schedule if there
1691 * is no timeout, or if it has yet to expire.
1692 */
1693 if (!timeout || timeout->task)
1694 schedule();
1695 }
1696 __set_current_state(TASK_RUNNING);
1697}
1698
Darren Hartf8010732009-04-03 13:40:40 -07001699/**
1700 * futex_wait_setup() - Prepare to wait on a futex
1701 * @uaddr: the futex userspace address
1702 * @val: the expected value
1703 * @fshared: whether the futex is shared (1) or not (0)
1704 * @q: the associated futex_q
1705 * @hb: storage for hash_bucket pointer to be returned to caller
1706 *
1707 * Setup the futex_q and locate the hash_bucket. Get the futex value and
1708 * compare it with the expected value. Handle atomic faults internally.
1709 * Return with the hb lock held and a q.key reference on success, and unlocked
1710 * with no q.key reference on failure.
1711 *
1712 * Returns:
1713 * 0 - uaddr contains val and hb has been locked
1714 * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
1715 */
1716static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,
1717 struct futex_q *q, struct futex_hash_bucket **hb)
1718{
1719 u32 uval;
1720 int ret;
1721
1722 /*
1723 * Access the page AFTER the hash-bucket is locked.
1724 * Order is important:
1725 *
1726 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1727 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1728 *
1729 * The basic logical guarantee of a futex is that it blocks ONLY
1730 * if cond(var) is known to be true at the time of blocking, for
1731 * any cond. If we queued after testing *uaddr, that would open
1732 * a race condition where we could block indefinitely with
1733 * cond(var) false, which would violate the guarantee.
1734 *
1735 * A consequence is that futex_wait() can return zero and absorb
1736 * a wakeup when *uaddr != val on entry to the syscall. This is
1737 * rare, but normal.
1738 */
1739retry:
1740 q->key = FUTEX_KEY_INIT;
Thomas Gleixner521c1802009-05-20 09:02:28 +02001741 ret = get_futex_key(uaddr, fshared, &q->key, VERIFY_READ);
Darren Hartf8010732009-04-03 13:40:40 -07001742 if (unlikely(ret != 0))
Darren Harta5a2a0c2009-04-10 09:50:05 -07001743 return ret;
Darren Hartf8010732009-04-03 13:40:40 -07001744
1745retry_private:
1746 *hb = queue_lock(q);
1747
1748 ret = get_futex_value_locked(&uval, uaddr);
1749
1750 if (ret) {
1751 queue_unlock(q, *hb);
1752
1753 ret = get_user(uval, uaddr);
1754 if (ret)
1755 goto out;
1756
1757 if (!fshared)
1758 goto retry_private;
1759
1760 put_futex_key(fshared, &q->key);
1761 goto retry;
1762 }
1763
1764 if (uval != val) {
1765 queue_unlock(q, *hb);
1766 ret = -EWOULDBLOCK;
1767 }
1768
1769out:
1770 if (ret)
1771 put_futex_key(fshared, &q->key);
1772 return ret;
1773}
1774
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001775static int futex_wait(u32 __user *uaddr, int fshared,
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001776 u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777{
Darren Hartca5f9522009-04-03 13:39:33 -07001778 struct hrtimer_sleeper timeout, *to = NULL;
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001779 struct restart_block *restart;
Ingo Molnare2970f22006-06-27 02:54:47 -07001780 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781 struct futex_q q;
Ingo Molnare2970f22006-06-27 02:54:47 -07001782 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783
Thomas Gleixnercd689982008-02-01 17:45:14 +01001784 if (!bitset)
1785 return -EINVAL;
1786
Ingo Molnarc87e2832006-06-27 02:54:58 -07001787 q.pi_state = NULL;
Thomas Gleixnercd689982008-02-01 17:45:14 +01001788 q.bitset = bitset;
Darren Hart52400ba2009-04-03 13:40:49 -07001789 q.rt_waiter = NULL;
Darren Hart84bc4af2009-08-13 17:36:53 -07001790 q.requeue_pi_key = NULL;
Darren Hartca5f9522009-04-03 13:39:33 -07001791
1792 if (abs_time) {
1793 to = &timeout;
1794
1795 hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
1796 CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1797 hrtimer_init_sleeper(to, current);
1798 hrtimer_set_expires_range_ns(&to->timer, *abs_time,
1799 current->timer_slack_ns);
1800 }
1801
Thomas Gleixnerd58e6572009-10-13 20:40:43 +02001802retry:
Darren Hartf8010732009-04-03 13:40:40 -07001803 /* Prepare to wait on uaddr. */
1804 ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
1805 if (ret)
Darren Hart42d35d42008-12-29 15:49:53 -08001806 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807
Darren Hartca5f9522009-04-03 13:39:33 -07001808 /* queue_me and wait for wakeup, timeout, or a signal. */
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +02001809 futex_wait_queue_me(hb, &q, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001810
1811 /* If we were woken (and unqueued), we succeeded, whatever. */
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001812 ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001813 if (!unqueue_me(&q))
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001814 goto out_put_key;
1815 ret = -ETIMEDOUT;
Darren Hartca5f9522009-04-03 13:39:33 -07001816 if (to && !to->task)
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001817 goto out_put_key;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001818
Ingo Molnare2970f22006-06-27 02:54:47 -07001819 /*
Thomas Gleixnerd58e6572009-10-13 20:40:43 +02001820 * We expect signal_pending(current), but we might be the
1821 * victim of a spurious wakeup as well.
Ingo Molnare2970f22006-06-27 02:54:47 -07001822 */
Thomas Gleixnerd58e6572009-10-13 20:40:43 +02001823 if (!signal_pending(current)) {
1824 put_futex_key(fshared, &q.key);
1825 goto retry;
1826 }
1827
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001828 ret = -ERESTARTSYS;
Pierre Peifferc19384b2007-05-09 02:35:02 -07001829 if (!abs_time)
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001830 goto out_put_key;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001831
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001832 restart = &current_thread_info()->restart_block;
1833 restart->fn = futex_wait_restart;
1834 restart->futex.uaddr = (u32 *)uaddr;
1835 restart->futex.val = val;
1836 restart->futex.time = abs_time->tv64;
1837 restart->futex.bitset = bitset;
Darren Harta72188d2009-04-03 13:40:22 -07001838 restart->futex.flags = FLAGS_HAS_TIMEOUT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001840 if (fshared)
1841 restart->futex.flags |= FLAGS_SHARED;
1842 if (clockrt)
1843 restart->futex.flags |= FLAGS_CLOCKRT;
1844
1845 ret = -ERESTART_RESTARTBLOCK;
1846
1847out_put_key:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001848 put_futex_key(fshared, &q.key);
Darren Hart42d35d42008-12-29 15:49:53 -08001849out:
Darren Hartca5f9522009-04-03 13:39:33 -07001850 if (to) {
1851 hrtimer_cancel(&to->timer);
1852 destroy_hrtimer_on_stack(&to->timer);
1853 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001854 return ret;
1855}
1856
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001857
1858static long futex_wait_restart(struct restart_block *restart)
1859{
Steven Rostedtce6bd422007-12-05 15:46:09 +01001860 u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001861 int fshared = 0;
Darren Harta72188d2009-04-03 13:40:22 -07001862 ktime_t t, *tp = NULL;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001863
Darren Harta72188d2009-04-03 13:40:22 -07001864 if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
1865 t.tv64 = restart->futex.time;
1866 tp = &t;
1867 }
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001868 restart->fn = do_no_restart_syscall;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001869 if (restart->futex.flags & FLAGS_SHARED)
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001870 fshared = 1;
Darren Harta72188d2009-04-03 13:40:22 -07001871 return (long)futex_wait(uaddr, fshared, restart->futex.val, tp,
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001872 restart->futex.bitset,
1873 restart->futex.flags & FLAGS_CLOCKRT);
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001874}
1875
1876
Ingo Molnarc87e2832006-06-27 02:54:58 -07001877/*
1878 * Userspace tried a 0 -> TID atomic transition of the futex value
1879 * and failed. The kernel side here does the whole locking operation:
1880 * if there are waiters then it will block, it does PI, etc. (Due to
1881 * races the kernel might see a 0 value of the futex too.)
1882 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001883static int futex_lock_pi(u32 __user *uaddr, int fshared,
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001884 int detect, ktime_t *time, int trylock)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001885{
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001886 struct hrtimer_sleeper timeout, *to = NULL;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001887 struct futex_hash_bucket *hb;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001888 struct futex_q q;
Darren Hartdd973992009-04-03 13:40:02 -07001889 int res, ret;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001890
1891 if (refill_pi_state_cache())
1892 return -ENOMEM;
1893
Pierre Peifferc19384b2007-05-09 02:35:02 -07001894 if (time) {
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001895 to = &timeout;
Thomas Gleixner237fc6e2008-04-30 00:55:04 -07001896 hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
1897 HRTIMER_MODE_ABS);
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001898 hrtimer_init_sleeper(to, current);
Arjan van de Vencc584b22008-09-01 15:02:30 -07001899 hrtimer_set_expires(&to->timer, *time);
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001900 }
1901
Ingo Molnarc87e2832006-06-27 02:54:58 -07001902 q.pi_state = NULL;
Darren Hart52400ba2009-04-03 13:40:49 -07001903 q.rt_waiter = NULL;
Darren Hart84bc4af2009-08-13 17:36:53 -07001904 q.requeue_pi_key = NULL;
Darren Hart42d35d42008-12-29 15:49:53 -08001905retry:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001906 q.key = FUTEX_KEY_INIT;
Thomas Gleixner64d13042009-05-18 21:20:10 +02001907 ret = get_futex_key(uaddr, fshared, &q.key, VERIFY_WRITE);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001908 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -08001909 goto out;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001910
Darren Harte4dc5b72009-03-12 00:56:13 -07001911retry_private:
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001912 hb = queue_lock(&q);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001913
Darren Hartbab5bc92009-04-07 23:23:50 -07001914 ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001915 if (unlikely(ret)) {
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001916 switch (ret) {
Darren Hart1a520842009-04-03 13:39:52 -07001917 case 1:
1918 /* We got the lock. */
1919 ret = 0;
1920 goto out_unlock_put_key;
1921 case -EFAULT:
1922 goto uaddr_faulted;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001923 case -EAGAIN:
1924 /*
1925 * Task is exiting and we just wait for the
1926 * exit to complete.
1927 */
1928 queue_unlock(&q, hb);
Darren Hartde87fcc2009-03-12 00:55:46 -07001929 put_futex_key(fshared, &q.key);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001930 cond_resched();
1931 goto retry;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001932 default:
Darren Hart42d35d42008-12-29 15:49:53 -08001933 goto out_unlock_put_key;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001934 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001935 }
1936
1937 /*
1938 * Only actually queue now that the atomic ops are done:
1939 */
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001940 queue_me(&q, hb);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001941
Ingo Molnarc87e2832006-06-27 02:54:58 -07001942 WARN_ON(!q.pi_state);
1943 /*
1944 * Block on the PI mutex:
1945 */
1946 if (!trylock)
1947 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1948 else {
1949 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1950 /* Fixup the trylock return value: */
1951 ret = ret ? 0 : -EWOULDBLOCK;
1952 }
1953
Vernon Mauerya99e4e42006-07-01 04:35:42 -07001954 spin_lock(q.lock_ptr);
Darren Hartdd973992009-04-03 13:40:02 -07001955 /*
1956 * Fixup the pi_state owner and possibly acquire the lock if we
1957 * haven't already.
1958 */
1959 res = fixup_owner(uaddr, fshared, &q, !ret);
1960 /*
1961 * If fixup_owner() returned an error, proprogate that. If it acquired
1962 * the lock, clear our -ETIMEDOUT or -EINTR.
1963 */
1964 if (res)
1965 ret = (res < 0) ? res : 0;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001966
Darren Harte8f63862009-03-12 00:56:06 -07001967 /*
Darren Hartdd973992009-04-03 13:40:02 -07001968 * If fixup_owner() faulted and was unable to handle the fault, unlock
1969 * it and return the fault to userspace.
Darren Harte8f63862009-03-12 00:56:06 -07001970 */
1971 if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current))
1972 rt_mutex_unlock(&q.pi_state->pi_mutex);
1973
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001974 /* Unqueue and drop the lock */
1975 unqueue_me_pi(&q);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001976
Darren Hartdd973992009-04-03 13:40:02 -07001977 goto out;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001978
Darren Hart42d35d42008-12-29 15:49:53 -08001979out_unlock_put_key:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001980 queue_unlock(&q, hb);
1981
Darren Hart42d35d42008-12-29 15:49:53 -08001982out_put_key:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001983 put_futex_key(fshared, &q.key);
Darren Hart42d35d42008-12-29 15:49:53 -08001984out:
Thomas Gleixner237fc6e2008-04-30 00:55:04 -07001985 if (to)
1986 destroy_hrtimer_on_stack(&to->timer);
Darren Hartdd973992009-04-03 13:40:02 -07001987 return ret != -EINTR ? ret : -ERESTARTNOINTR;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001988
Darren Hart42d35d42008-12-29 15:49:53 -08001989uaddr_faulted:
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001990 queue_unlock(&q, hb);
1991
Thomas Gleixnerd0725992009-06-11 23:15:43 +02001992 ret = fault_in_user_writeable(uaddr);
Darren Harte4dc5b72009-03-12 00:56:13 -07001993 if (ret)
1994 goto out_put_key;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001995
Darren Harte4dc5b72009-03-12 00:56:13 -07001996 if (!fshared)
1997 goto retry_private;
1998
1999 put_futex_key(fshared, &q.key);
2000 goto retry;
Ingo Molnarc87e2832006-06-27 02:54:58 -07002001}
2002
2003/*
Ingo Molnarc87e2832006-06-27 02:54:58 -07002004 * Userspace attempted a TID -> 0 atomic transition, and failed.
2005 * This is the in-kernel slowpath: we look up the PI state (if any),
2006 * and do the rt-mutex unlock.
2007 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02002008static int futex_unlock_pi(u32 __user *uaddr, int fshared)
Ingo Molnarc87e2832006-06-27 02:54:58 -07002009{
2010 struct futex_hash_bucket *hb;
2011 struct futex_q *this, *next;
2012 u32 uval;
Pierre Peifferec92d082007-05-09 02:35:00 -07002013 struct plist_head *head;
Peter Zijlstra38d47c12008-09-26 19:32:20 +02002014 union futex_key key = FUTEX_KEY_INIT;
Darren Harte4dc5b72009-03-12 00:56:13 -07002015 int ret;
Ingo Molnarc87e2832006-06-27 02:54:58 -07002016
2017retry:
2018 if (get_user(uval, uaddr))
2019 return -EFAULT;
2020 /*
2021 * We release only a lock we actually own:
2022 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07002023 if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
Ingo Molnarc87e2832006-06-27 02:54:58 -07002024 return -EPERM;
Ingo Molnarc87e2832006-06-27 02:54:58 -07002025
Thomas Gleixner64d13042009-05-18 21:20:10 +02002026 ret = get_futex_key(uaddr, fshared, &key, VERIFY_WRITE);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002027 if (unlikely(ret != 0))
2028 goto out;
2029
2030 hb = hash_futex(&key);
2031 spin_lock(&hb->lock);
2032
Ingo Molnarc87e2832006-06-27 02:54:58 -07002033 /*
2034 * To avoid races, try to do the TID -> 0 atomic transition
2035 * again. If it succeeds then we can return without waking
2036 * anyone else up:
2037 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07002038 if (!(uval & FUTEX_OWNER_DIED))
Pavel Emelyanovb4888932007-10-18 23:40:14 -07002039 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07002040
Ingo Molnarc87e2832006-06-27 02:54:58 -07002041
2042 if (unlikely(uval == -EFAULT))
2043 goto pi_faulted;
2044 /*
2045 * Rare case: we managed to release the lock atomically,
2046 * no need to wake anyone else up:
2047 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07002048 if (unlikely(uval == task_pid_vnr(current)))
Ingo Molnarc87e2832006-06-27 02:54:58 -07002049 goto out_unlock;
2050
2051 /*
2052 * Ok, other tasks may need to be woken up - check waiters
2053 * and do the wakeup if necessary:
2054 */
2055 head = &hb->chain;
2056
Pierre Peifferec92d082007-05-09 02:35:00 -07002057 plist_for_each_entry_safe(this, next, head, list) {
Ingo Molnarc87e2832006-06-27 02:54:58 -07002058 if (!match_futex (&this->key, &key))
2059 continue;
2060 ret = wake_futex_pi(uaddr, uval, this);
2061 /*
2062 * The atomic access to the futex value
2063 * generated a pagefault, so retry the
2064 * user-access and the wakeup:
2065 */
2066 if (ret == -EFAULT)
2067 goto pi_faulted;
2068 goto out_unlock;
2069 }
2070 /*
2071 * No waiters - kernel unlocks the futex:
2072 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002073 if (!(uval & FUTEX_OWNER_DIED)) {
2074 ret = unlock_futex_pi(uaddr, uval);
2075 if (ret == -EFAULT)
2076 goto pi_faulted;
2077 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07002078
2079out_unlock:
2080 spin_unlock(&hb->lock);
Peter Zijlstra38d47c12008-09-26 19:32:20 +02002081 put_futex_key(fshared, &key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002082
Darren Hart42d35d42008-12-29 15:49:53 -08002083out:
Ingo Molnarc87e2832006-06-27 02:54:58 -07002084 return ret;
2085
2086pi_faulted:
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07002087 spin_unlock(&hb->lock);
Darren Harte4dc5b72009-03-12 00:56:13 -07002088 put_futex_key(fshared, &key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002089
Thomas Gleixnerd0725992009-06-11 23:15:43 +02002090 ret = fault_in_user_writeable(uaddr);
Darren Hartb5686362008-12-18 15:06:34 -08002091 if (!ret)
Ingo Molnarc87e2832006-06-27 02:54:58 -07002092 goto retry;
2093
Linus Torvalds1da177e2005-04-16 15:20:36 -07002094 return ret;
2095}
2096
Darren Hart52400ba2009-04-03 13:40:49 -07002097/**
2098 * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex
2099 * @hb: the hash_bucket futex_q was original enqueued on
2100 * @q: the futex_q woken while waiting to be requeued
2101 * @key2: the futex_key of the requeue target futex
2102 * @timeout: the timeout associated with the wait (NULL if none)
2103 *
2104 * Detect if the task was woken on the initial futex as opposed to the requeue
2105 * target futex. If so, determine if it was a timeout or a signal that caused
2106 * the wakeup and return the appropriate error code to the caller. Must be
2107 * called with the hb lock held.
2108 *
2109 * Returns
2110 * 0 - no early wakeup detected
Thomas Gleixner1c840c12009-05-20 09:22:40 +02002111 * <0 - -ETIMEDOUT or -ERESTARTNOINTR
Darren Hart52400ba2009-04-03 13:40:49 -07002112 */
2113static inline
2114int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
2115 struct futex_q *q, union futex_key *key2,
2116 struct hrtimer_sleeper *timeout)
2117{
2118 int ret = 0;
2119
2120 /*
2121 * With the hb lock held, we avoid races while we process the wakeup.
2122 * We only need to hold hb (and not hb2) to ensure atomicity as the
2123 * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb.
2124 * It can't be requeued from uaddr2 to something else since we don't
2125 * support a PI aware source futex for requeue.
2126 */
2127 if (!match_futex(&q->key, key2)) {
2128 WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr));
2129 /*
2130 * We were woken prior to requeue by a timeout or a signal.
2131 * Unqueue the futex_q and determine which it was.
2132 */
2133 plist_del(&q->list, &q->list.plist);
Darren Hart52400ba2009-04-03 13:40:49 -07002134
Thomas Gleixnerd58e6572009-10-13 20:40:43 +02002135 /* Handle spurious wakeups gracefully */
Thomas Gleixner11df6dd2009-10-28 20:26:48 +01002136 ret = -EWOULDBLOCK;
Darren Hart52400ba2009-04-03 13:40:49 -07002137 if (timeout && !timeout->task)
2138 ret = -ETIMEDOUT;
Thomas Gleixnerd58e6572009-10-13 20:40:43 +02002139 else if (signal_pending(current))
Thomas Gleixner1c840c12009-05-20 09:22:40 +02002140 ret = -ERESTARTNOINTR;
Darren Hart52400ba2009-04-03 13:40:49 -07002141 }
2142 return ret;
2143}
2144
2145/**
2146 * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
Darren Hart56ec1602009-09-21 22:29:59 -07002147 * @uaddr: the futex we initially wait on (non-pi)
Darren Hart52400ba2009-04-03 13:40:49 -07002148 * @fshared: whether the futexes are shared (1) or not (0). They must be
2149 * the same type, no requeueing from private to shared, etc.
2150 * @val: the expected value of uaddr
2151 * @abs_time: absolute timeout
Darren Hart56ec1602009-09-21 22:29:59 -07002152 * @bitset: 32 bit wakeup bitset set by userspace, defaults to all
Darren Hart52400ba2009-04-03 13:40:49 -07002153 * @clockrt: whether to use CLOCK_REALTIME (1) or CLOCK_MONOTONIC (0)
2154 * @uaddr2: the pi futex we will take prior to returning to user-space
2155 *
2156 * The caller will wait on uaddr and will be requeued by futex_requeue() to
2157 * uaddr2 which must be PI aware. Normal wakeup will wake on uaddr2 and
2158 * complete the acquisition of the rt_mutex prior to returning to userspace.
2159 * This ensures the rt_mutex maintains an owner when it has waiters; without
2160 * one, the pi logic wouldn't know which task to boost/deboost, if there was a
2161 * need to.
2162 *
2163 * We call schedule in futex_wait_queue_me() when we enqueue and return there
2164 * via the following:
2165 * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue()
Darren Hartcc6db4e2009-07-31 16:20:10 -07002166 * 2) wakeup on uaddr2 after a requeue
2167 * 3) signal
2168 * 4) timeout
Darren Hart52400ba2009-04-03 13:40:49 -07002169 *
Darren Hartcc6db4e2009-07-31 16:20:10 -07002170 * If 3, cleanup and return -ERESTARTNOINTR.
Darren Hart52400ba2009-04-03 13:40:49 -07002171 *
2172 * If 2, we may then block on trying to take the rt_mutex and return via:
2173 * 5) successful lock
2174 * 6) signal
2175 * 7) timeout
2176 * 8) other lock acquisition failure
2177 *
Darren Hartcc6db4e2009-07-31 16:20:10 -07002178 * If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
Darren Hart52400ba2009-04-03 13:40:49 -07002179 *
2180 * If 4 or 7, we cleanup and return with -ETIMEDOUT.
2181 *
2182 * Returns:
2183 * 0 - On success
2184 * <0 - On error
2185 */
2186static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
2187 u32 val, ktime_t *abs_time, u32 bitset,
2188 int clockrt, u32 __user *uaddr2)
2189{
2190 struct hrtimer_sleeper timeout, *to = NULL;
2191 struct rt_mutex_waiter rt_waiter;
2192 struct rt_mutex *pi_mutex = NULL;
Darren Hart52400ba2009-04-03 13:40:49 -07002193 struct futex_hash_bucket *hb;
2194 union futex_key key2;
2195 struct futex_q q;
2196 int res, ret;
Darren Hart52400ba2009-04-03 13:40:49 -07002197
2198 if (!bitset)
2199 return -EINVAL;
2200
2201 if (abs_time) {
2202 to = &timeout;
2203 hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
2204 CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
2205 hrtimer_init_sleeper(to, current);
2206 hrtimer_set_expires_range_ns(&to->timer, *abs_time,
2207 current->timer_slack_ns);
2208 }
2209
2210 /*
2211 * The waiter is allocated on our stack, manipulated by the requeue
2212 * code while we sleep on uaddr.
2213 */
2214 debug_rt_mutex_init_waiter(&rt_waiter);
2215 rt_waiter.task = NULL;
2216
Darren Hart52400ba2009-04-03 13:40:49 -07002217 key2 = FUTEX_KEY_INIT;
Thomas Gleixner521c1802009-05-20 09:02:28 +02002218 ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_WRITE);
Darren Hart52400ba2009-04-03 13:40:49 -07002219 if (unlikely(ret != 0))
2220 goto out;
2221
Darren Hart84bc4af2009-08-13 17:36:53 -07002222 q.pi_state = NULL;
2223 q.bitset = bitset;
2224 q.rt_waiter = &rt_waiter;
2225 q.requeue_pi_key = &key2;
2226
Darren Hart52400ba2009-04-03 13:40:49 -07002227 /* Prepare to wait on uaddr. */
2228 ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
Thomas Gleixnerc8b15a72009-05-20 09:18:50 +02002229 if (ret)
2230 goto out_key2;
Darren Hart52400ba2009-04-03 13:40:49 -07002231
2232 /* Queue the futex_q, drop the hb lock, wait for wakeup. */
Thomas Gleixnerf1a11e02009-05-05 19:21:40 +02002233 futex_wait_queue_me(hb, &q, to);
Darren Hart52400ba2009-04-03 13:40:49 -07002234
2235 spin_lock(&hb->lock);
2236 ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to);
2237 spin_unlock(&hb->lock);
2238 if (ret)
2239 goto out_put_keys;
2240
2241 /*
2242 * In order for us to be here, we know our q.key == key2, and since
2243 * we took the hb->lock above, we also know that futex_requeue() has
2244 * completed and we no longer have to concern ourselves with a wakeup
2245 * race with the atomic proxy lock acquition by the requeue code.
2246 */
2247
2248 /* Check if the requeue code acquired the second futex for us. */
2249 if (!q.rt_waiter) {
2250 /*
2251 * Got the lock. We might not be the anticipated owner if we
2252 * did a lock-steal - fix up the PI-state in that case.
2253 */
2254 if (q.pi_state && (q.pi_state->owner != current)) {
2255 spin_lock(q.lock_ptr);
2256 ret = fixup_pi_state_owner(uaddr2, &q, current,
2257 fshared);
2258 spin_unlock(q.lock_ptr);
2259 }
2260 } else {
2261 /*
2262 * We have been woken up by futex_unlock_pi(), a timeout, or a
2263 * signal. futex_unlock_pi() will not destroy the lock_ptr nor
2264 * the pi_state.
2265 */
2266 WARN_ON(!&q.pi_state);
2267 pi_mutex = &q.pi_state->pi_mutex;
2268 ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1);
2269 debug_rt_mutex_free_waiter(&rt_waiter);
2270
2271 spin_lock(q.lock_ptr);
2272 /*
2273 * Fixup the pi_state owner and possibly acquire the lock if we
2274 * haven't already.
2275 */
2276 res = fixup_owner(uaddr2, fshared, &q, !ret);
2277 /*
2278 * If fixup_owner() returned an error, proprogate that. If it
Darren Hart56ec1602009-09-21 22:29:59 -07002279 * acquired the lock, clear -ETIMEDOUT or -EINTR.
Darren Hart52400ba2009-04-03 13:40:49 -07002280 */
2281 if (res)
2282 ret = (res < 0) ? res : 0;
2283
2284 /* Unqueue and drop the lock. */
2285 unqueue_me_pi(&q);
2286 }
2287
2288 /*
2289 * If fixup_pi_state_owner() faulted and was unable to handle the
2290 * fault, unlock the rt_mutex and return the fault to userspace.
2291 */
2292 if (ret == -EFAULT) {
2293 if (rt_mutex_owner(pi_mutex) == current)
2294 rt_mutex_unlock(pi_mutex);
2295 } else if (ret == -EINTR) {
Darren Hart52400ba2009-04-03 13:40:49 -07002296 /*
Darren Hartcc6db4e2009-07-31 16:20:10 -07002297 * We've already been requeued, but cannot restart by calling
2298 * futex_lock_pi() directly. We could restart this syscall, but
2299 * it would detect that the user space "val" changed and return
2300 * -EWOULDBLOCK. Save the overhead of the restart and return
2301 * -EWOULDBLOCK directly.
Darren Hart52400ba2009-04-03 13:40:49 -07002302 */
Thomas Gleixner20708872009-05-19 23:04:59 +02002303 ret = -EWOULDBLOCK;
Darren Hart52400ba2009-04-03 13:40:49 -07002304 }
2305
2306out_put_keys:
2307 put_futex_key(fshared, &q.key);
Thomas Gleixnerc8b15a72009-05-20 09:18:50 +02002308out_key2:
Darren Hart52400ba2009-04-03 13:40:49 -07002309 put_futex_key(fshared, &key2);
2310
2311out:
2312 if (to) {
2313 hrtimer_cancel(&to->timer);
2314 destroy_hrtimer_on_stack(&to->timer);
2315 }
2316 return ret;
2317}
2318
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002319/*
2320 * Support for robust futexes: the kernel cleans up held futexes at
2321 * thread exit time.
2322 *
2323 * Implementation: user-space maintains a per-thread list of locks it
2324 * is holding. Upon do_exit(), the kernel carefully walks this list,
2325 * and marks all locks that are owned by this thread with the
Ingo Molnarc87e2832006-06-27 02:54:58 -07002326 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002327 * always manipulated with the lock held, so the list is private and
2328 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
2329 * field, to allow the kernel to clean up if the thread dies after
2330 * acquiring the lock, but just before it could have added itself to
2331 * the list. There can only be one such pending lock.
2332 */
2333
2334/**
Darren Hartd96ee562009-09-21 22:30:22 -07002335 * sys_set_robust_list() - Set the robust-futex list head of a task
2336 * @head: pointer to the list-head
2337 * @len: length of the list-head, as userspace expects
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002338 */
Heiko Carstens836f92a2009-01-14 14:14:33 +01002339SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
2340 size_t, len)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002341{
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002342 if (!futex_cmpxchg_enabled)
2343 return -ENOSYS;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002344 /*
2345 * The kernel knows only one size for now:
2346 */
2347 if (unlikely(len != sizeof(*head)))
2348 return -EINVAL;
2349
2350 current->robust_list = head;
2351
2352 return 0;
2353}
2354
2355/**
Darren Hartd96ee562009-09-21 22:30:22 -07002356 * sys_get_robust_list() - Get the robust-futex list head of a task
2357 * @pid: pid of the process [zero for current task]
2358 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
2359 * @len_ptr: pointer to a length field, the kernel fills in the header size
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002360 */
Heiko Carstens836f92a2009-01-14 14:14:33 +01002361SYSCALL_DEFINE3(get_robust_list, int, pid,
2362 struct robust_list_head __user * __user *, head_ptr,
2363 size_t __user *, len_ptr)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002364{
Al Viroba46df92006-10-10 22:46:07 +01002365 struct robust_list_head __user *head;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002366 unsigned long ret;
David Howellsc69e8d92008-11-14 10:39:19 +11002367 const struct cred *cred = current_cred(), *pcred;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002368
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002369 if (!futex_cmpxchg_enabled)
2370 return -ENOSYS;
2371
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002372 if (!pid)
2373 head = current->robust_list;
2374 else {
2375 struct task_struct *p;
2376
2377 ret = -ESRCH;
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07002378 rcu_read_lock();
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -07002379 p = find_task_by_vpid(pid);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002380 if (!p)
2381 goto err_unlock;
2382 ret = -EPERM;
David Howellsc69e8d92008-11-14 10:39:19 +11002383 pcred = __task_cred(p);
2384 if (cred->euid != pcred->euid &&
2385 cred->euid != pcred->uid &&
David Howells76aac0e2008-11-14 10:39:12 +11002386 !capable(CAP_SYS_PTRACE))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002387 goto err_unlock;
2388 head = p->robust_list;
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07002389 rcu_read_unlock();
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002390 }
2391
2392 if (put_user(sizeof(*head), len_ptr))
2393 return -EFAULT;
2394 return put_user(head, head_ptr);
2395
2396err_unlock:
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07002397 rcu_read_unlock();
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002398
2399 return ret;
2400}
2401
2402/*
2403 * Process a futex-list entry, check whether it's owned by the
2404 * dying task, and do notification if so:
2405 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002406int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002407{
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002408 u32 uval, nval, mval;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002409
Ingo Molnar8f17d3a2006-03-27 01:16:27 -08002410retry:
2411 if (get_user(uval, uaddr))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002412 return -1;
2413
Pavel Emelyanovb4888932007-10-18 23:40:14 -07002414 if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002415 /*
2416 * Ok, this dying thread is truly holding a futex
2417 * of interest. Set the OWNER_DIED bit atomically
2418 * via cmpxchg, and if the value had FUTEX_WAITERS
2419 * set, wake up a waiter (if any). (We have to do a
2420 * futex_wake() even if OWNER_DIED is already set -
2421 * to handle the rare but possible case of recursive
2422 * thread-death.) The rest of the cleanup is done in
2423 * userspace.
2424 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002425 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
2426 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
2427
Ingo Molnarc87e2832006-06-27 02:54:58 -07002428 if (nval == -EFAULT)
2429 return -1;
2430
2431 if (nval != uval)
Ingo Molnar8f17d3a2006-03-27 01:16:27 -08002432 goto retry;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002433
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002434 /*
2435 * Wake robust non-PI futexes here. The wakeup of
2436 * PI futexes happens in exit_pi_state():
2437 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07002438 if (!pi && (uval & FUTEX_WAITERS))
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02002439 futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002440 }
2441 return 0;
2442}
2443
2444/*
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002445 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
2446 */
2447static inline int fetch_robust_entry(struct robust_list __user **entry,
Al Viroba46df92006-10-10 22:46:07 +01002448 struct robust_list __user * __user *head,
2449 int *pi)
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002450{
2451 unsigned long uentry;
2452
Al Viroba46df92006-10-10 22:46:07 +01002453 if (get_user(uentry, (unsigned long __user *)head))
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002454 return -EFAULT;
2455
Al Viroba46df92006-10-10 22:46:07 +01002456 *entry = (void __user *)(uentry & ~1UL);
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002457 *pi = uentry & 1;
2458
2459 return 0;
2460}
2461
2462/*
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002463 * Walk curr->robust_list (very carefully, it's a userspace list!)
2464 * and mark any locks found there dead, and notify any waiters.
2465 *
2466 * We silently return on any sign of list-walking problem.
2467 */
2468void exit_robust_list(struct task_struct *curr)
2469{
2470 struct robust_list_head __user *head = curr->robust_list;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002471 struct robust_list __user *entry, *next_entry, *pending;
2472 unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002473 unsigned long futex_offset;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002474 int rc;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002475
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002476 if (!futex_cmpxchg_enabled)
2477 return;
2478
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002479 /*
2480 * Fetch the list head (which was registered earlier, via
2481 * sys_set_robust_list()):
2482 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002483 if (fetch_robust_entry(&entry, &head->list.next, &pi))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002484 return;
2485 /*
2486 * Fetch the relative futex offset:
2487 */
2488 if (get_user(futex_offset, &head->futex_offset))
2489 return;
2490 /*
2491 * Fetch any possibly pending lock-add first, and handle it
2492 * if it exists:
2493 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002494 if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002495 return;
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002496
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002497 next_entry = NULL; /* avoid warning with gcc */
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002498 while (entry != &head->list) {
2499 /*
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002500 * Fetch the next entry in the list before calling
2501 * handle_futex_death:
2502 */
2503 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
2504 /*
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002505 * A pending lock might already be on the list, so
Ingo Molnarc87e2832006-06-27 02:54:58 -07002506 * don't process it twice:
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002507 */
2508 if (entry != pending)
Al Viroba46df92006-10-10 22:46:07 +01002509 if (handle_futex_death((void __user *)entry + futex_offset,
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002510 curr, pi))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002511 return;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002512 if (rc)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002513 return;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002514 entry = next_entry;
2515 pi = next_pi;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002516 /*
2517 * Avoid excessively long or circular lists:
2518 */
2519 if (!--limit)
2520 break;
2521
2522 cond_resched();
2523 }
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002524
2525 if (pending)
2526 handle_futex_death((void __user *)pending + futex_offset,
2527 curr, pip);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002528}
2529
Pierre Peifferc19384b2007-05-09 02:35:02 -07002530long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
Ingo Molnare2970f22006-06-27 02:54:47 -07002531 u32 __user *uaddr2, u32 val2, u32 val3)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002532{
Thomas Gleixner1acdac12008-11-20 10:02:53 -08002533 int clockrt, ret = -ENOSYS;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002534 int cmd = op & FUTEX_CMD_MASK;
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02002535 int fshared = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002536
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002537 if (!(op & FUTEX_PRIVATE_FLAG))
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02002538 fshared = 1;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002539
Thomas Gleixner1acdac12008-11-20 10:02:53 -08002540 clockrt = op & FUTEX_CLOCK_REALTIME;
Darren Hart52400ba2009-04-03 13:40:49 -07002541 if (clockrt && cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
Thomas Gleixner1acdac12008-11-20 10:02:53 -08002542 return -ENOSYS;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002543
2544 switch (cmd) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002545 case FUTEX_WAIT:
Thomas Gleixnercd689982008-02-01 17:45:14 +01002546 val3 = FUTEX_BITSET_MATCH_ANY;
2547 case FUTEX_WAIT_BITSET:
Thomas Gleixner1acdac12008-11-20 10:02:53 -08002548 ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002549 break;
2550 case FUTEX_WAKE:
Thomas Gleixnercd689982008-02-01 17:45:14 +01002551 val3 = FUTEX_BITSET_MATCH_ANY;
2552 case FUTEX_WAKE_BITSET:
2553 ret = futex_wake(uaddr, fshared, val, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002554 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002555 case FUTEX_REQUEUE:
Darren Hart52400ba2009-04-03 13:40:49 -07002556 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 break;
2558 case FUTEX_CMP_REQUEUE:
Darren Hart52400ba2009-04-03 13:40:49 -07002559 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
2560 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002561 break;
Jakub Jelinek4732efb2005-09-06 15:16:25 -07002562 case FUTEX_WAKE_OP:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002563 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
Jakub Jelinek4732efb2005-09-06 15:16:25 -07002564 break;
Ingo Molnarc87e2832006-06-27 02:54:58 -07002565 case FUTEX_LOCK_PI:
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002566 if (futex_cmpxchg_enabled)
2567 ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002568 break;
2569 case FUTEX_UNLOCK_PI:
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002570 if (futex_cmpxchg_enabled)
2571 ret = futex_unlock_pi(uaddr, fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002572 break;
2573 case FUTEX_TRYLOCK_PI:
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002574 if (futex_cmpxchg_enabled)
2575 ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002576 break;
Darren Hart52400ba2009-04-03 13:40:49 -07002577 case FUTEX_WAIT_REQUEUE_PI:
2578 val3 = FUTEX_BITSET_MATCH_ANY;
2579 ret = futex_wait_requeue_pi(uaddr, fshared, val, timeout, val3,
2580 clockrt, uaddr2);
2581 break;
Darren Hart52400ba2009-04-03 13:40:49 -07002582 case FUTEX_CMP_REQUEUE_PI:
2583 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
2584 1);
2585 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002586 default:
2587 ret = -ENOSYS;
2588 }
2589 return ret;
2590}
2591
2592
Heiko Carstens17da2bd2009-01-14 14:14:10 +01002593SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
2594 struct timespec __user *, utime, u32 __user *, uaddr2,
2595 u32, val3)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596{
Pierre Peifferc19384b2007-05-09 02:35:02 -07002597 struct timespec ts;
2598 ktime_t t, *tp = NULL;
Ingo Molnare2970f22006-06-27 02:54:47 -07002599 u32 val2 = 0;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002600 int cmd = op & FUTEX_CMD_MASK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002601
Thomas Gleixnercd689982008-02-01 17:45:14 +01002602 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
Darren Hart52400ba2009-04-03 13:40:49 -07002603 cmd == FUTEX_WAIT_BITSET ||
2604 cmd == FUTEX_WAIT_REQUEUE_PI)) {
Pierre Peifferc19384b2007-05-09 02:35:02 -07002605 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002606 return -EFAULT;
Pierre Peifferc19384b2007-05-09 02:35:02 -07002607 if (!timespec_valid(&ts))
Thomas Gleixner9741ef962006-03-31 02:31:32 -08002608 return -EINVAL;
Pierre Peifferc19384b2007-05-09 02:35:02 -07002609
2610 t = timespec_to_ktime(ts);
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002611 if (cmd == FUTEX_WAIT)
Thomas Gleixner5a7780e2008-02-13 09:20:43 +01002612 t = ktime_add_safe(ktime_get(), t);
Pierre Peifferc19384b2007-05-09 02:35:02 -07002613 tp = &t;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002614 }
2615 /*
Darren Hart52400ba2009-04-03 13:40:49 -07002616 * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*.
Andreas Schwabf54f0982007-07-31 00:38:51 -07002617 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002618 */
Andreas Schwabf54f0982007-07-31 00:38:51 -07002619 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
Darren Hartba9c22f2009-04-20 22:22:22 -07002620 cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
Ingo Molnare2970f22006-06-27 02:54:47 -07002621 val2 = (u32) (unsigned long) utime;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622
Pierre Peifferc19384b2007-05-09 02:35:02 -07002623 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002624}
2625
Benjamin Herrenschmidtf6d107f2008-03-27 14:52:15 +11002626static int __init futex_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627{
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002628 u32 curval;
Thomas Gleixner3e4ab742008-02-23 15:23:55 -08002629 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002631 /*
2632 * This will fail and we want it. Some arch implementations do
2633 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2634 * functionality. We want to know that before we call in any
2635 * of the complex code paths. Also we want to prevent
2636 * registration of robust lists in that case. NULL is
2637 * guaranteed to fault and we get -EFAULT on functional
2638 * implementation, the non functional ones will return
2639 * -ENOSYS.
2640 */
2641 curval = cmpxchg_futex_value_locked(NULL, 0, 0);
2642 if (curval == -EFAULT)
2643 futex_cmpxchg_enabled = 1;
2644
Thomas Gleixner3e4ab742008-02-23 15:23:55 -08002645 for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
2646 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
2647 spin_lock_init(&futex_queues[i].lock);
2648 }
2649
Linus Torvalds1da177e2005-04-16 15:20:36 -07002650 return 0;
2651}
Benjamin Herrenschmidtf6d107f2008-03-27 14:52:15 +11002652__initcall(futex_init);