Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 1 | #include <linux/types.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 2 | #include <linux/errno.h> |
Jiri Slaby | 8b3ffa1 | 2011-11-16 16:27:10 +0100 | [diff] [blame] | 3 | #include <linux/kmod.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 4 | #include <linux/sched.h> |
| 5 | #include <linux/interrupt.h> |
| 6 | #include <linux/tty.h> |
| 7 | #include <linux/tty_driver.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 8 | #include <linux/file.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 9 | #include <linux/mm.h> |
| 10 | #include <linux/string.h> |
| 11 | #include <linux/slab.h> |
| 12 | #include <linux/poll.h> |
| 13 | #include <linux/proc_fs.h> |
| 14 | #include <linux/init.h> |
| 15 | #include <linux/module.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 16 | #include <linux/device.h> |
| 17 | #include <linux/wait.h> |
| 18 | #include <linux/bitops.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 19 | #include <linux/seq_file.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 20 | #include <linux/uaccess.h> |
Jiri Slaby | 0c73c08 | 2011-11-16 16:27:09 +0100 | [diff] [blame] | 21 | #include <linux/ratelimit.h> |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 22 | |
| 23 | /* |
| 24 | * This guards the refcounted line discipline lists. The lock |
| 25 | * must be taken with irqs off because there are hangup path |
| 26 | * callers who will do ldisc lookups and cannot sleep. |
| 27 | */ |
| 28 | |
| 29 | static DEFINE_SPINLOCK(tty_ldisc_lock); |
| 30 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 31 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 32 | /* Line disc dispatch table */ |
| 33 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; |
| 34 | |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 35 | static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) |
| 36 | { |
| 37 | if (ld) |
| 38 | atomic_inc(&ld->users); |
| 39 | return ld; |
| 40 | } |
| 41 | |
Linus Torvalds | cbe9352 | 2009-08-03 14:54:56 -0700 | [diff] [blame] | 42 | static void put_ldisc(struct tty_ldisc *ld) |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 43 | { |
Linus Torvalds | cbe9352 | 2009-08-03 14:54:56 -0700 | [diff] [blame] | 44 | unsigned long flags; |
| 45 | |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 46 | if (WARN_ON_ONCE(!ld)) |
| 47 | return; |
| 48 | |
| 49 | /* |
| 50 | * If this is the last user, free the ldisc, and |
| 51 | * release the ldisc ops. |
Linus Torvalds | cbe9352 | 2009-08-03 14:54:56 -0700 | [diff] [blame] | 52 | * |
| 53 | * We really want an "atomic_dec_and_lock_irqsave()", |
| 54 | * but we don't have it, so this does it by hand. |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 55 | */ |
Linus Torvalds | cbe9352 | 2009-08-03 14:54:56 -0700 | [diff] [blame] | 56 | local_irq_save(flags); |
| 57 | if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 58 | struct tty_ldisc_ops *ldo = ld->ops; |
| 59 | |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 60 | ldo->refcount--; |
| 61 | module_put(ldo->owner); |
| 62 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
Linus Torvalds | cbe9352 | 2009-08-03 14:54:56 -0700 | [diff] [blame] | 63 | |
| 64 | kfree(ld); |
| 65 | return; |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 66 | } |
Linus Torvalds | cbe9352 | 2009-08-03 14:54:56 -0700 | [diff] [blame] | 67 | local_irq_restore(flags); |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 68 | wake_up(&tty_ldisc_idle); |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 69 | } |
| 70 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 71 | /** |
| 72 | * tty_register_ldisc - install a line discipline |
| 73 | * @disc: ldisc number |
| 74 | * @new_ldisc: pointer to the ldisc object |
| 75 | * |
| 76 | * Installs a new line discipline into the kernel. The discipline |
| 77 | * is set up as unreferenced and then made available to the kernel |
| 78 | * from this point onwards. |
| 79 | * |
| 80 | * Locking: |
| 81 | * takes tty_ldisc_lock to guard against ldisc races |
| 82 | */ |
| 83 | |
| 84 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) |
| 85 | { |
| 86 | unsigned long flags; |
| 87 | int ret = 0; |
| 88 | |
| 89 | if (disc < N_TTY || disc >= NR_LDISCS) |
| 90 | return -EINVAL; |
| 91 | |
| 92 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
| 93 | tty_ldiscs[disc] = new_ldisc; |
| 94 | new_ldisc->num = disc; |
| 95 | new_ldisc->refcount = 0; |
| 96 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
| 97 | |
| 98 | return ret; |
| 99 | } |
| 100 | EXPORT_SYMBOL(tty_register_ldisc); |
| 101 | |
| 102 | /** |
| 103 | * tty_unregister_ldisc - unload a line discipline |
| 104 | * @disc: ldisc number |
| 105 | * @new_ldisc: pointer to the ldisc object |
| 106 | * |
| 107 | * Remove a line discipline from the kernel providing it is not |
| 108 | * currently in use. |
| 109 | * |
| 110 | * Locking: |
| 111 | * takes tty_ldisc_lock to guard against ldisc races |
| 112 | */ |
| 113 | |
| 114 | int tty_unregister_ldisc(int disc) |
| 115 | { |
| 116 | unsigned long flags; |
| 117 | int ret = 0; |
| 118 | |
| 119 | if (disc < N_TTY || disc >= NR_LDISCS) |
| 120 | return -EINVAL; |
| 121 | |
| 122 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
| 123 | if (tty_ldiscs[disc]->refcount) |
| 124 | ret = -EBUSY; |
| 125 | else |
| 126 | tty_ldiscs[disc] = NULL; |
| 127 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
| 128 | |
| 129 | return ret; |
| 130 | } |
| 131 | EXPORT_SYMBOL(tty_unregister_ldisc); |
| 132 | |
Linus Torvalds | f0de0e8 | 2009-08-03 16:00:15 -0700 | [diff] [blame] | 133 | static struct tty_ldisc_ops *get_ldops(int disc) |
| 134 | { |
| 135 | unsigned long flags; |
| 136 | struct tty_ldisc_ops *ldops, *ret; |
| 137 | |
| 138 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
| 139 | ret = ERR_PTR(-EINVAL); |
| 140 | ldops = tty_ldiscs[disc]; |
| 141 | if (ldops) { |
| 142 | ret = ERR_PTR(-EAGAIN); |
| 143 | if (try_module_get(ldops->owner)) { |
| 144 | ldops->refcount++; |
| 145 | ret = ldops; |
| 146 | } |
| 147 | } |
| 148 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
| 149 | return ret; |
| 150 | } |
| 151 | |
| 152 | static void put_ldops(struct tty_ldisc_ops *ldops) |
| 153 | { |
| 154 | unsigned long flags; |
| 155 | |
| 156 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
| 157 | ldops->refcount--; |
| 158 | module_put(ldops->owner); |
| 159 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
| 160 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 161 | |
| 162 | /** |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 163 | * tty_ldisc_get - take a reference to an ldisc |
| 164 | * @disc: ldisc number |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 165 | * |
| 166 | * Takes a reference to a line discipline. Deals with refcounts and |
| 167 | * module locking counts. Returns NULL if the discipline is not available. |
| 168 | * Returns a pointer to the discipline and bumps the ref count if it is |
| 169 | * available |
| 170 | * |
| 171 | * Locking: |
| 172 | * takes tty_ldisc_lock to guard against ldisc races |
| 173 | */ |
| 174 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 175 | static struct tty_ldisc *tty_ldisc_get(int disc) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 176 | { |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 177 | struct tty_ldisc *ld; |
Linus Torvalds | 182274f | 2009-08-03 16:01:28 -0700 | [diff] [blame] | 178 | struct tty_ldisc_ops *ldops; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 179 | |
| 180 | if (disc < N_TTY || disc >= NR_LDISCS) |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 181 | return ERR_PTR(-EINVAL); |
Linus Torvalds | 182274f | 2009-08-03 16:01:28 -0700 | [diff] [blame] | 182 | |
| 183 | /* |
| 184 | * Get the ldisc ops - we may need to request them to be loaded |
| 185 | * dynamically and try again. |
| 186 | */ |
| 187 | ldops = get_ldops(disc); |
| 188 | if (IS_ERR(ldops)) { |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 189 | request_module("tty-ldisc-%d", disc); |
Linus Torvalds | 182274f | 2009-08-03 16:01:28 -0700 | [diff] [blame] | 190 | ldops = get_ldops(disc); |
| 191 | if (IS_ERR(ldops)) |
| 192 | return ERR_CAST(ldops); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 193 | } |
Linus Torvalds | 182274f | 2009-08-03 16:01:28 -0700 | [diff] [blame] | 194 | |
| 195 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); |
| 196 | if (ld == NULL) { |
| 197 | put_ldops(ldops); |
| 198 | return ERR_PTR(-ENOMEM); |
| 199 | } |
| 200 | |
| 201 | ld->ops = ldops; |
| 202 | atomic_set(&ld->users, 1); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 203 | return ld; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 204 | } |
| 205 | |
Alan Cox | 852e99d | 2009-06-11 12:51:41 +0100 | [diff] [blame] | 206 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 207 | { |
| 208 | return (*pos < NR_LDISCS) ? pos : NULL; |
| 209 | } |
| 210 | |
Alan Cox | 852e99d | 2009-06-11 12:51:41 +0100 | [diff] [blame] | 211 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 212 | { |
| 213 | (*pos)++; |
| 214 | return (*pos < NR_LDISCS) ? pos : NULL; |
| 215 | } |
| 216 | |
| 217 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) |
| 218 | { |
| 219 | } |
| 220 | |
| 221 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) |
| 222 | { |
| 223 | int i = *(loff_t *)v; |
Linus Torvalds | f0de0e8 | 2009-08-03 16:00:15 -0700 | [diff] [blame] | 224 | struct tty_ldisc_ops *ldops; |
Alan Cox | 852e99d | 2009-06-11 12:51:41 +0100 | [diff] [blame] | 225 | |
Linus Torvalds | f0de0e8 | 2009-08-03 16:00:15 -0700 | [diff] [blame] | 226 | ldops = get_ldops(i); |
| 227 | if (IS_ERR(ldops)) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 228 | return 0; |
Linus Torvalds | f0de0e8 | 2009-08-03 16:00:15 -0700 | [diff] [blame] | 229 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
| 230 | put_ldops(ldops); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 231 | return 0; |
| 232 | } |
| 233 | |
| 234 | static const struct seq_operations tty_ldiscs_seq_ops = { |
| 235 | .start = tty_ldiscs_seq_start, |
| 236 | .next = tty_ldiscs_seq_next, |
| 237 | .stop = tty_ldiscs_seq_stop, |
| 238 | .show = tty_ldiscs_seq_show, |
| 239 | }; |
| 240 | |
| 241 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) |
| 242 | { |
| 243 | return seq_open(file, &tty_ldiscs_seq_ops); |
| 244 | } |
| 245 | |
| 246 | const struct file_operations tty_ldiscs_proc_fops = { |
| 247 | .owner = THIS_MODULE, |
| 248 | .open = proc_tty_ldiscs_open, |
| 249 | .read = seq_read, |
| 250 | .llseek = seq_lseek, |
| 251 | .release = seq_release, |
| 252 | }; |
| 253 | |
| 254 | /** |
| 255 | * tty_ldisc_assign - set ldisc on a tty |
| 256 | * @tty: tty to assign |
| 257 | * @ld: line discipline |
| 258 | * |
| 259 | * Install an instance of a line discipline into a tty structure. The |
Alan Cox | 8d2ead7 | 2009-06-16 17:00:26 +0100 | [diff] [blame] | 260 | * ldisc must have a reference count above zero to ensure it remains. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 261 | * The tty instance refcount starts at zero. |
| 262 | * |
| 263 | * Locking: |
| 264 | * Caller must hold references |
| 265 | */ |
| 266 | |
| 267 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) |
| 268 | { |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 269 | tty->ldisc = ld; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 270 | } |
| 271 | |
| 272 | /** |
| 273 | * tty_ldisc_try - internal helper |
| 274 | * @tty: the tty |
| 275 | * |
| 276 | * Make a single attempt to grab and bump the refcount on |
| 277 | * the tty ldisc. Return 0 on failure or 1 on success. This is |
| 278 | * used to implement both the waiting and non waiting versions |
| 279 | * of tty_ldisc_ref |
| 280 | * |
| 281 | * Locking: takes tty_ldisc_lock |
| 282 | */ |
| 283 | |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 284 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 285 | { |
| 286 | unsigned long flags; |
| 287 | struct tty_ldisc *ld; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 288 | |
| 289 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 290 | ld = NULL; |
| 291 | if (test_bit(TTY_LDISC, &tty->flags)) |
| 292 | ld = get_ldisc(tty->ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 293 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 294 | return ld; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 295 | } |
| 296 | |
| 297 | /** |
| 298 | * tty_ldisc_ref_wait - wait for the tty ldisc |
| 299 | * @tty: tty device |
| 300 | * |
| 301 | * Dereference the line discipline for the terminal and take a |
| 302 | * reference to it. If the line discipline is in flux then |
| 303 | * wait patiently until it changes. |
| 304 | * |
| 305 | * Note: Must not be called from an IRQ/timer context. The caller |
| 306 | * must also be careful not to hold other locks that will deadlock |
| 307 | * against a discipline change, such as an existing ldisc reference |
| 308 | * (which we check for) |
| 309 | * |
| 310 | * Locking: call functions take tty_ldisc_lock |
| 311 | */ |
| 312 | |
| 313 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) |
| 314 | { |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 315 | struct tty_ldisc *ld; |
| 316 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 317 | /* wait_event is a macro */ |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 318 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
| 319 | return ld; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 320 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 321 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
| 322 | |
| 323 | /** |
| 324 | * tty_ldisc_ref - get the tty ldisc |
| 325 | * @tty: tty device |
| 326 | * |
| 327 | * Dereference the line discipline for the terminal and take a |
| 328 | * reference to it. If the line discipline is in flux then |
| 329 | * return NULL. Can be called from IRQ and timer functions. |
| 330 | * |
| 331 | * Locking: called functions take tty_ldisc_lock |
| 332 | */ |
| 333 | |
| 334 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) |
| 335 | { |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 336 | return tty_ldisc_try(tty); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 337 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 338 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
| 339 | |
| 340 | /** |
| 341 | * tty_ldisc_deref - free a tty ldisc reference |
| 342 | * @ld: reference to free up |
| 343 | * |
| 344 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May |
| 345 | * be called in IRQ context. |
| 346 | * |
| 347 | * Locking: takes tty_ldisc_lock |
| 348 | */ |
| 349 | |
| 350 | void tty_ldisc_deref(struct tty_ldisc *ld) |
| 351 | { |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 352 | put_ldisc(ld); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 353 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 354 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
| 355 | |
Linus Torvalds | 65b7704 | 2009-08-03 11:11:19 -0700 | [diff] [blame] | 356 | static inline void tty_ldisc_put(struct tty_ldisc *ld) |
| 357 | { |
| 358 | put_ldisc(ld); |
| 359 | } |
| 360 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 361 | /** |
| 362 | * tty_ldisc_enable - allow ldisc use |
| 363 | * @tty: terminal to activate ldisc on |
| 364 | * |
| 365 | * Set the TTY_LDISC flag when the line discipline can be called |
Alan Cox | c9b3976 | 2009-01-02 13:44:56 +0000 | [diff] [blame] | 366 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
| 367 | * changing flag to indicate any ldisc change is now over. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 368 | * |
Alan Cox | c9b3976 | 2009-01-02 13:44:56 +0000 | [diff] [blame] | 369 | * Note: nobody should set the TTY_LDISC bit except via this function. |
| 370 | * Clearing directly is allowed. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 371 | */ |
| 372 | |
| 373 | void tty_ldisc_enable(struct tty_struct *tty) |
| 374 | { |
| 375 | set_bit(TTY_LDISC, &tty->flags); |
Alan Cox | c9b3976 | 2009-01-02 13:44:56 +0000 | [diff] [blame] | 376 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 377 | wake_up(&tty_ldisc_wait); |
| 378 | } |
| 379 | |
| 380 | /** |
Alan Cox | f2c4c65 | 2009-06-11 12:50:58 +0100 | [diff] [blame] | 381 | * tty_ldisc_flush - flush line discipline queue |
| 382 | * @tty: tty |
| 383 | * |
| 384 | * Flush the line discipline queue (if any) for this tty. If there |
| 385 | * is no line discipline active this is a no-op. |
| 386 | */ |
| 387 | |
| 388 | void tty_ldisc_flush(struct tty_struct *tty) |
| 389 | { |
| 390 | struct tty_ldisc *ld = tty_ldisc_ref(tty); |
| 391 | if (ld) { |
| 392 | if (ld->ops->flush_buffer) |
| 393 | ld->ops->flush_buffer(tty); |
| 394 | tty_ldisc_deref(ld); |
| 395 | } |
| 396 | tty_buffer_flush(tty); |
| 397 | } |
Alan Cox | f2c4c65 | 2009-06-11 12:50:58 +0100 | [diff] [blame] | 398 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
| 399 | |
| 400 | /** |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 401 | * tty_set_termios_ldisc - set ldisc field |
| 402 | * @tty: tty structure |
| 403 | * @num: line discipline number |
| 404 | * |
| 405 | * This is probably overkill for real world processors but |
| 406 | * they are not on hot paths so a little discipline won't do |
| 407 | * any harm. |
| 408 | * |
Jeron Susan | 279b700 | 2016-10-18 11:10:24 +0800 | [diff] [blame] | 409 | * The line discipline-related tty_struct fields are reset to |
| 410 | * prevent the ldisc driver from re-using stale information for |
| 411 | * the new ldisc instance. |
| 412 | * |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 413 | * Locking: takes termios_mutex |
| 414 | */ |
| 415 | |
| 416 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) |
| 417 | { |
| 418 | mutex_lock(&tty->termios_mutex); |
| 419 | tty->termios->c_line = num; |
| 420 | mutex_unlock(&tty->termios_mutex); |
Jeron Susan | 279b700 | 2016-10-18 11:10:24 +0800 | [diff] [blame] | 421 | |
| 422 | tty->disc_data = NULL; |
| 423 | tty->receive_room = 0; |
| 424 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 425 | } |
| 426 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 427 | /** |
| 428 | * tty_ldisc_open - open a line discipline |
| 429 | * @tty: tty we are opening the ldisc on |
| 430 | * @ld: discipline to open |
| 431 | * |
| 432 | * A helper opening method. Also a convenient debugging and check |
| 433 | * point. |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 434 | * |
| 435 | * Locking: always called with BTM already held. |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 436 | */ |
| 437 | |
| 438 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) |
| 439 | { |
| 440 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); |
Alan Cox | f18f949 | 2009-11-30 13:18:35 +0000 | [diff] [blame] | 441 | if (ld->ops->open) { |
| 442 | int ret; |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 443 | /* BTM here locks versus a hangup event */ |
Alan Cox | f18f949 | 2009-11-30 13:18:35 +0000 | [diff] [blame] | 444 | ret = ld->ops->open(tty); |
Jiri Slaby | 7f90cfc | 2010-11-25 00:27:54 +0100 | [diff] [blame] | 445 | if (ret) |
| 446 | clear_bit(TTY_LDISC_OPEN, &tty->flags); |
Alan Cox | f18f949 | 2009-11-30 13:18:35 +0000 | [diff] [blame] | 447 | return ret; |
| 448 | } |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 449 | return 0; |
| 450 | } |
| 451 | |
| 452 | /** |
| 453 | * tty_ldisc_close - close a line discipline |
| 454 | * @tty: tty we are opening the ldisc on |
| 455 | * @ld: discipline to close |
| 456 | * |
| 457 | * A helper close method. Also a convenient debugging and check |
| 458 | * point. |
| 459 | */ |
| 460 | |
| 461 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) |
| 462 | { |
| 463 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
| 464 | clear_bit(TTY_LDISC_OPEN, &tty->flags); |
| 465 | if (ld->ops->close) |
| 466 | ld->ops->close(tty); |
| 467 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 468 | |
| 469 | /** |
| 470 | * tty_ldisc_restore - helper for tty ldisc change |
| 471 | * @tty: tty to recover |
| 472 | * @old: previous ldisc |
| 473 | * |
| 474 | * Restore the previous line discipline or N_TTY when a line discipline |
| 475 | * change fails due to an open error |
| 476 | */ |
| 477 | |
| 478 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) |
| 479 | { |
| 480 | char buf[64]; |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 481 | struct tty_ldisc *new_ldisc; |
| 482 | int r; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 483 | |
| 484 | /* There is an outstanding reference here so this is safe */ |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 485 | old = tty_ldisc_get(old->ops->num); |
| 486 | WARN_ON(IS_ERR(old)); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 487 | tty_ldisc_assign(tty, old); |
| 488 | tty_set_termios_ldisc(tty, old->ops->num); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 489 | if (tty_ldisc_open(tty, old) < 0) { |
| 490 | tty_ldisc_put(old); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 491 | /* This driver is always present */ |
Alan Cox | 852e99d | 2009-06-11 12:51:41 +0100 | [diff] [blame] | 492 | new_ldisc = tty_ldisc_get(N_TTY); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 493 | if (IS_ERR(new_ldisc)) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 494 | panic("n_tty: get"); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 495 | tty_ldisc_assign(tty, new_ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 496 | tty_set_termios_ldisc(tty, N_TTY); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 497 | r = tty_ldisc_open(tty, new_ldisc); |
| 498 | if (r < 0) |
| 499 | panic("Couldn't open N_TTY ldisc for " |
| 500 | "%s --- error %d.", |
| 501 | tty_name(tty, buf), r); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 502 | } |
| 503 | } |
| 504 | |
| 505 | /** |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 506 | * tty_ldisc_halt - shut down the line discipline |
Alan Cox | e8b70e7 | 2009-06-11 12:48:02 +0100 | [diff] [blame] | 507 | * @tty: tty device |
| 508 | * |
| 509 | * Shut down the line discipline and work queue for this tty device. |
| 510 | * The TTY_LDISC flag being cleared ensures no further references can |
| 511 | * be obtained while the delayed work queue halt ensures that no more |
| 512 | * data is fed to the ldisc. |
| 513 | * |
Linus Torvalds | 5c58cef | 2009-08-25 09:12:43 -0700 | [diff] [blame] | 514 | * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) |
| 515 | * in order to make sure any currently executing ldisc work is also |
| 516 | * flushed. |
Alan Cox | e8b70e7 | 2009-06-11 12:48:02 +0100 | [diff] [blame] | 517 | */ |
| 518 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 519 | static int tty_ldisc_halt(struct tty_struct *tty) |
Alan Cox | e8b70e7 | 2009-06-11 12:48:02 +0100 | [diff] [blame] | 520 | { |
| 521 | clear_bit(TTY_LDISC, &tty->flags); |
Linus Torvalds | f23eb2b | 2011-03-22 16:17:32 -0700 | [diff] [blame] | 522 | return cancel_work_sync(&tty->buf.work); |
Alan Cox | e8b70e7 | 2009-06-11 12:48:02 +0100 | [diff] [blame] | 523 | } |
| 524 | |
| 525 | /** |
Tejun Heo | 0a1f1a0 | 2011-01-24 17:54:12 +0100 | [diff] [blame] | 526 | * tty_ldisc_flush_works - flush all works of a tty |
| 527 | * @tty: tty device to flush works for |
| 528 | * |
| 529 | * Sync flush all works belonging to @tty. |
| 530 | */ |
| 531 | static void tty_ldisc_flush_works(struct tty_struct *tty) |
| 532 | { |
| 533 | flush_work_sync(&tty->hangup_work); |
| 534 | flush_work_sync(&tty->SAK_work); |
Linus Torvalds | f23eb2b | 2011-03-22 16:17:32 -0700 | [diff] [blame] | 535 | flush_work_sync(&tty->buf.work); |
Tejun Heo | 0a1f1a0 | 2011-01-24 17:54:12 +0100 | [diff] [blame] | 536 | } |
| 537 | |
| 538 | /** |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 539 | * tty_ldisc_wait_idle - wait for the ldisc to become idle |
| 540 | * @tty: tty to wait for |
Jiri Slaby | df92d05 | 2011-11-16 16:27:07 +0100 | [diff] [blame] | 541 | * @timeout: for how long to wait at most |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 542 | * |
| 543 | * Wait for the line discipline to become idle. The discipline must |
| 544 | * have been halted for this to guarantee it remains idle. |
| 545 | */ |
Jiri Slaby | df92d05 | 2011-11-16 16:27:07 +0100 | [diff] [blame] | 546 | static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 547 | { |
Jiri Slaby | df92d05 | 2011-11-16 16:27:07 +0100 | [diff] [blame] | 548 | long ret; |
Jiri Slaby | 92f6fa0 | 2011-06-05 14:16:16 +0200 | [diff] [blame] | 549 | ret = wait_event_timeout(tty_ldisc_idle, |
Jiri Slaby | df92d05 | 2011-11-16 16:27:07 +0100 | [diff] [blame] | 550 | atomic_read(&tty->ldisc->users) == 1, timeout); |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 551 | return ret > 0 ? 0 : -EBUSY; |
| 552 | } |
| 553 | |
| 554 | /** |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 555 | * tty_set_ldisc - set line discipline |
| 556 | * @tty: the terminal to set |
| 557 | * @ldisc: the line discipline |
| 558 | * |
| 559 | * Set the discipline of a tty line. Must be called from a process |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 560 | * context. The ldisc change logic has to protect itself against any |
| 561 | * overlapping ldisc change (including on the other end of pty pairs), |
| 562 | * the close of one side of a tty/pty pair, and eventually hangup. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 563 | * |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 564 | * Locking: takes tty_ldisc_lock, termios_mutex |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 565 | */ |
| 566 | |
| 567 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) |
| 568 | { |
| 569 | int retval; |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 570 | struct tty_ldisc *o_ldisc, *new_ldisc; |
| 571 | int work, o_work = 0; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 572 | struct tty_struct *o_tty; |
| 573 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 574 | new_ldisc = tty_ldisc_get(ldisc); |
| 575 | if (IS_ERR(new_ldisc)) |
| 576 | return PTR_ERR(new_ldisc); |
| 577 | |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 578 | tty_lock(); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 579 | /* |
| 580 | * We need to look at the tty locking here for pty/tty pairs |
| 581 | * when both sides try to change in parallel. |
| 582 | */ |
| 583 | |
| 584 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
| 585 | |
| 586 | |
| 587 | /* |
| 588 | * Check the no-op case |
| 589 | */ |
| 590 | |
| 591 | if (tty->ldisc->ops->num == ldisc) { |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 592 | tty_unlock(); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 593 | tty_ldisc_put(new_ldisc); |
| 594 | return 0; |
| 595 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 596 | |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 597 | tty_unlock(); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 598 | /* |
| 599 | * Problem: What do we do if this blocks ? |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 600 | * We could deadlock here |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 601 | */ |
| 602 | |
| 603 | tty_wait_until_sent(tty, 0); |
| 604 | |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 605 | tty_lock(); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 606 | mutex_lock(&tty->ldisc_mutex); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 607 | |
| 608 | /* |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 609 | * We could be midstream of another ldisc change which has |
| 610 | * dropped the lock during processing. If so we need to wait. |
| 611 | */ |
| 612 | |
| 613 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { |
| 614 | mutex_unlock(&tty->ldisc_mutex); |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 615 | tty_unlock(); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 616 | wait_event(tty_ldisc_wait, |
| 617 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 618 | tty_lock(); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 619 | mutex_lock(&tty->ldisc_mutex); |
| 620 | } |
Alan Cox | eeb89d9 | 2009-11-30 13:18:29 +0000 | [diff] [blame] | 621 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 622 | set_bit(TTY_LDISC_CHANGING, &tty->flags); |
Alan Cox | 852e99d | 2009-06-11 12:51:41 +0100 | [diff] [blame] | 623 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 624 | /* |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 625 | * No more input please, we are switching. The new ldisc |
| 626 | * will update this value in the ldisc open function |
| 627 | */ |
| 628 | |
| 629 | tty->receive_room = 0; |
| 630 | |
| 631 | o_ldisc = tty->ldisc; |
Alan Cox | eeb89d9 | 2009-11-30 13:18:29 +0000 | [diff] [blame] | 632 | |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 633 | tty_unlock(); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 634 | /* |
| 635 | * Make sure we don't change while someone holds a |
| 636 | * reference to the line discipline. The TTY_LDISC bit |
| 637 | * prevents anyone taking a reference once it is clear. |
| 638 | * We need the lock to avoid racing reference takers. |
Alan Cox | c9b3976 | 2009-01-02 13:44:56 +0000 | [diff] [blame] | 639 | * |
| 640 | * We must clear the TTY_LDISC bit here to avoid a livelock |
| 641 | * with a userspace app continually trying to use the tty in |
| 642 | * parallel to the change and re-referencing the tty. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 643 | */ |
| 644 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 645 | work = tty_ldisc_halt(tty); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 646 | if (o_tty) |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 647 | o_work = tty_ldisc_halt(o_tty); |
| 648 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 649 | /* |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 650 | * Wait for ->hangup_work and ->buf.work handlers to terminate. |
| 651 | * We must drop the mutex here in case a hangup is also in process. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 652 | */ |
| 653 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 654 | mutex_unlock(&tty->ldisc_mutex); |
| 655 | |
Tejun Heo | 0a1f1a0 | 2011-01-24 17:54:12 +0100 | [diff] [blame] | 656 | tty_ldisc_flush_works(tty); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 657 | |
Jiri Slaby | df92d05 | 2011-11-16 16:27:07 +0100 | [diff] [blame] | 658 | retval = tty_ldisc_wait_idle(tty, 5 * HZ); |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 659 | |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 660 | tty_lock(); |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 661 | mutex_lock(&tty->ldisc_mutex); |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 662 | |
| 663 | /* handle wait idle failure locked */ |
| 664 | if (retval) { |
| 665 | tty_ldisc_put(new_ldisc); |
| 666 | goto enable; |
| 667 | } |
| 668 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 669 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
| 670 | /* We were raced by the hangup method. It will have stomped |
| 671 | the ldisc data and closed the ldisc down */ |
| 672 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
| 673 | mutex_unlock(&tty->ldisc_mutex); |
| 674 | tty_ldisc_put(new_ldisc); |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 675 | tty_unlock(); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 676 | return -EIO; |
| 677 | } |
| 678 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 679 | /* Shutdown the current discipline. */ |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 680 | tty_ldisc_close(tty, o_ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 681 | |
| 682 | /* Now set up the new line discipline. */ |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 683 | tty_ldisc_assign(tty, new_ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 684 | tty_set_termios_ldisc(tty, ldisc); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 685 | |
| 686 | retval = tty_ldisc_open(tty, new_ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 687 | if (retval < 0) { |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 688 | /* Back to the old one or N_TTY if we can't */ |
| 689 | tty_ldisc_put(new_ldisc); |
| 690 | tty_ldisc_restore(tty, o_ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 691 | } |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 692 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 693 | /* At this point we hold a reference to the new ldisc and a |
| 694 | a reference to the old ldisc. If we ended up flipping back |
| 695 | to the existing ldisc we have two references to it */ |
| 696 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 697 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 698 | tty->ops->set_ldisc(tty); |
| 699 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 700 | tty_ldisc_put(o_ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 701 | |
Jiri Slaby | 100eeae | 2010-10-31 23:17:51 +0100 | [diff] [blame] | 702 | enable: |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 703 | /* |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 704 | * Allow ldisc referencing to occur again |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 705 | */ |
| 706 | |
| 707 | tty_ldisc_enable(tty); |
| 708 | if (o_tty) |
| 709 | tty_ldisc_enable(o_tty); |
| 710 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 711 | /* Restart the work queue in case no characters kick it off. Safe if |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 712 | already running */ |
| 713 | if (work) |
Linus Torvalds | f23eb2b | 2011-03-22 16:17:32 -0700 | [diff] [blame] | 714 | schedule_work(&tty->buf.work); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 715 | if (o_work) |
Linus Torvalds | f23eb2b | 2011-03-22 16:17:32 -0700 | [diff] [blame] | 716 | schedule_work(&o_tty->buf.work); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 717 | mutex_unlock(&tty->ldisc_mutex); |
Arnd Bergmann | ec79d60 | 2010-06-01 22:53:01 +0200 | [diff] [blame] | 718 | tty_unlock(); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 719 | return retval; |
| 720 | } |
| 721 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 722 | /** |
| 723 | * tty_reset_termios - reset terminal state |
| 724 | * @tty: tty to reset |
| 725 | * |
| 726 | * Restore a terminal to the driver default state. |
| 727 | */ |
| 728 | |
| 729 | static void tty_reset_termios(struct tty_struct *tty) |
| 730 | { |
| 731 | mutex_lock(&tty->termios_mutex); |
| 732 | *tty->termios = tty->driver->init_termios; |
| 733 | tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); |
| 734 | tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); |
| 735 | mutex_unlock(&tty->termios_mutex); |
| 736 | } |
| 737 | |
| 738 | |
| 739 | /** |
| 740 | * tty_ldisc_reinit - reinitialise the tty ldisc |
| 741 | * @tty: tty to reinit |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 742 | * @ldisc: line discipline to reinitialize |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 743 | * |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 744 | * Switch the tty to a line discipline and leave the ldisc |
| 745 | * state closed |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 746 | */ |
| 747 | |
Philippe Rétornaz | 1c95ba1 | 2010-10-27 17:13:21 +0200 | [diff] [blame] | 748 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 749 | { |
Philippe Rétornaz | 1c95ba1 | 2010-10-27 17:13:21 +0200 | [diff] [blame] | 750 | struct tty_ldisc *ld = tty_ldisc_get(ldisc); |
| 751 | |
| 752 | if (IS_ERR(ld)) |
| 753 | return -1; |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 754 | |
| 755 | tty_ldisc_close(tty, tty->ldisc); |
| 756 | tty_ldisc_put(tty->ldisc); |
| 757 | tty->ldisc = NULL; |
| 758 | /* |
| 759 | * Switch the line discipline back |
| 760 | */ |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 761 | tty_ldisc_assign(tty, ld); |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 762 | tty_set_termios_ldisc(tty, ldisc); |
Philippe Rétornaz | 1c95ba1 | 2010-10-27 17:13:21 +0200 | [diff] [blame] | 763 | |
| 764 | return 0; |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 765 | } |
| 766 | |
| 767 | /** |
| 768 | * tty_ldisc_hangup - hangup ldisc reset |
| 769 | * @tty: tty being hung up |
| 770 | * |
| 771 | * Some tty devices reset their termios when they receive a hangup |
| 772 | * event. In that situation we must also switch back to N_TTY properly |
| 773 | * before we reset the termios data. |
| 774 | * |
| 775 | * Locking: We can take the ldisc mutex as the rest of the code is |
| 776 | * careful to allow for this. |
| 777 | * |
| 778 | * In the pty pair case this occurs in the close() path of the |
| 779 | * tty itself so we must be careful about locking rules. |
| 780 | */ |
| 781 | |
| 782 | void tty_ldisc_hangup(struct tty_struct *tty) |
| 783 | { |
| 784 | struct tty_ldisc *ld; |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 785 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
| 786 | int err = 0; |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 787 | |
| 788 | /* |
| 789 | * FIXME! What are the locking issues here? This may me overdoing |
| 790 | * things... This question is especially important now that we've |
| 791 | * removed the irqlock. |
| 792 | */ |
| 793 | ld = tty_ldisc_ref(tty); |
| 794 | if (ld != NULL) { |
| 795 | /* We may have no line discipline at this point */ |
| 796 | if (ld->ops->flush_buffer) |
| 797 | ld->ops->flush_buffer(tty); |
| 798 | tty_driver_flush_buffer(tty); |
| 799 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && |
| 800 | ld->ops->write_wakeup) |
| 801 | ld->ops->write_wakeup(tty); |
| 802 | if (ld->ops->hangup) |
| 803 | ld->ops->hangup(tty); |
| 804 | tty_ldisc_deref(ld); |
| 805 | } |
| 806 | /* |
| 807 | * FIXME: Once we trust the LDISC code better we can wait here for |
| 808 | * ldisc completion and fix the driver call race |
| 809 | */ |
| 810 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
| 811 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); |
| 812 | /* |
| 813 | * Shutdown the current line discipline, and reset it to |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 814 | * N_TTY if need be. |
| 815 | * |
| 816 | * Avoid racing set_ldisc or tty_ldisc_release |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 817 | */ |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 818 | mutex_lock(&tty->ldisc_mutex); |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 819 | |
| 820 | /* |
| 821 | * this is like tty_ldisc_halt, but we need to give up |
Linus Torvalds | f23eb2b | 2011-03-22 16:17:32 -0700 | [diff] [blame] | 822 | * the BTM before calling cancel_work_sync, which may |
| 823 | * need to wait for another function taking the BTM |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 824 | */ |
| 825 | clear_bit(TTY_LDISC, &tty->flags); |
| 826 | tty_unlock(); |
Linus Torvalds | f23eb2b | 2011-03-22 16:17:32 -0700 | [diff] [blame] | 827 | cancel_work_sync(&tty->buf.work); |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 828 | mutex_unlock(&tty->ldisc_mutex); |
Jiri Slaby | 0c73c08 | 2011-11-16 16:27:09 +0100 | [diff] [blame] | 829 | retry: |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 830 | tty_lock(); |
| 831 | mutex_lock(&tty->ldisc_mutex); |
| 832 | |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 833 | /* At this point we have a closed ldisc and we want to |
| 834 | reopen it. We could defer this to the next open but |
| 835 | it means auditing a lot of other paths so this is |
| 836 | a FIXME */ |
| 837 | if (tty->ldisc) { /* Not yet closed */ |
Jiri Slaby | 0c73c08 | 2011-11-16 16:27:09 +0100 | [diff] [blame] | 838 | if (atomic_read(&tty->ldisc->users) != 1) { |
| 839 | char cur_n[TASK_COMM_LEN], tty_n[64]; |
| 840 | long timeout = 3 * HZ; |
| 841 | tty_unlock(); |
| 842 | |
| 843 | while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) { |
| 844 | timeout = MAX_SCHEDULE_TIMEOUT; |
| 845 | printk_ratelimited(KERN_WARNING |
| 846 | "%s: waiting (%s) for %s took too long, but we keep waiting...\n", |
| 847 | __func__, get_task_comm(cur_n, current), |
| 848 | tty_name(tty, tty_n)); |
| 849 | } |
| 850 | mutex_unlock(&tty->ldisc_mutex); |
| 851 | goto retry; |
| 852 | } |
Jiri Slaby | 3004207 | 2011-11-16 16:27:08 +0100 | [diff] [blame] | 853 | |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 854 | if (reset == 0) { |
Philippe Rétornaz | 1c95ba1 | 2010-10-27 17:13:21 +0200 | [diff] [blame] | 855 | |
| 856 | if (!tty_ldisc_reinit(tty, tty->termios->c_line)) |
| 857 | err = tty_ldisc_open(tty, tty->ldisc); |
| 858 | else |
| 859 | err = 1; |
Alan Cox | c8d5004 | 2009-07-16 16:05:08 +0100 | [diff] [blame] | 860 | } |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 861 | /* If the re-open fails or we reset then go to N_TTY. The |
| 862 | N_TTY open cannot fail */ |
| 863 | if (reset || err) { |
Philippe Rétornaz | 1c95ba1 | 2010-10-27 17:13:21 +0200 | [diff] [blame] | 864 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 865 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
| 866 | } |
| 867 | tty_ldisc_enable(tty); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 868 | } |
Alan Cox | 638b964 | 2010-02-08 10:09:26 +0000 | [diff] [blame] | 869 | mutex_unlock(&tty->ldisc_mutex); |
| 870 | if (reset) |
| 871 | tty_reset_termios(tty); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 872 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 873 | |
| 874 | /** |
| 875 | * tty_ldisc_setup - open line discipline |
| 876 | * @tty: tty being shut down |
| 877 | * @o_tty: pair tty for pty/tty pairs |
| 878 | * |
| 879 | * Called during the initial open of a tty/pty pair in order to set up the |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 880 | * line disciplines and bind them to the tty. This has no locking issues |
| 881 | * as the device isn't yet active. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 882 | */ |
| 883 | |
| 884 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) |
| 885 | { |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 886 | struct tty_ldisc *ld = tty->ldisc; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 887 | int retval; |
| 888 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 889 | retval = tty_ldisc_open(tty, ld); |
| 890 | if (retval) |
| 891 | return retval; |
| 892 | |
| 893 | if (o_tty) { |
| 894 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 895 | if (retval) { |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 896 | tty_ldisc_close(tty, ld); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 897 | return retval; |
| 898 | } |
| 899 | tty_ldisc_enable(o_tty); |
| 900 | } |
| 901 | tty_ldisc_enable(tty); |
| 902 | return 0; |
| 903 | } |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 904 | /** |
| 905 | * tty_ldisc_release - release line discipline |
| 906 | * @tty: tty being shut down |
| 907 | * @o_tty: pair tty for pty/tty pairs |
| 908 | * |
Alan Cox | 852e99d | 2009-06-11 12:51:41 +0100 | [diff] [blame] | 909 | * Called during the final close of a tty/pty pair in order to shut down |
| 910 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 911 | * ldisc has not been opened. |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 912 | */ |
| 913 | |
| 914 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) |
| 915 | { |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 916 | /* |
| 917 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then |
| 918 | * kill any delayed work. As this is the final close it does not |
| 919 | * race with the set_ldisc code path. |
| 920 | */ |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 921 | |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 922 | tty_unlock(); |
Alan Cox | e8b70e7 | 2009-06-11 12:48:02 +0100 | [diff] [blame] | 923 | tty_ldisc_halt(tty); |
Tejun Heo | 0a1f1a0 | 2011-01-24 17:54:12 +0100 | [diff] [blame] | 924 | tty_ldisc_flush_works(tty); |
Arnd Bergmann | 60af22d | 2010-06-01 22:53:06 +0200 | [diff] [blame] | 925 | tty_lock(); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 926 | |
Alan Cox | c8d5004 | 2009-07-16 16:05:08 +0100 | [diff] [blame] | 927 | mutex_lock(&tty->ldisc_mutex); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 928 | /* |
Alan Cox | aef29bc | 2009-06-29 15:21:47 +0100 | [diff] [blame] | 929 | * Now kill off the ldisc |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 930 | */ |
Alan Cox | aef29bc | 2009-06-29 15:21:47 +0100 | [diff] [blame] | 931 | tty_ldisc_close(tty, tty->ldisc); |
| 932 | tty_ldisc_put(tty->ldisc); |
| 933 | /* Force an oops if we mess this up */ |
| 934 | tty->ldisc = NULL; |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 935 | |
Alan Cox | aef29bc | 2009-06-29 15:21:47 +0100 | [diff] [blame] | 936 | /* Ensure the next open requests the N_TTY ldisc */ |
| 937 | tty_set_termios_ldisc(tty, N_TTY); |
Alan Cox | c8d5004 | 2009-07-16 16:05:08 +0100 | [diff] [blame] | 938 | mutex_unlock(&tty->ldisc_mutex); |
Alan Cox | aef29bc | 2009-06-29 15:21:47 +0100 | [diff] [blame] | 939 | |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 940 | /* This will need doing differently if we need to lock */ |
| 941 | if (o_tty) |
| 942 | tty_ldisc_release(o_tty, NULL); |
Alan Cox | aef29bc | 2009-06-29 15:21:47 +0100 | [diff] [blame] | 943 | |
| 944 | /* And the memory resources remaining (buffers, termios) will be |
| 945 | disposed of when the kref hits zero */ |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 946 | } |
| 947 | |
| 948 | /** |
| 949 | * tty_ldisc_init - ldisc setup for new tty |
| 950 | * @tty: tty being allocated |
| 951 | * |
| 952 | * Set up the line discipline objects for a newly allocated tty. Note that |
| 953 | * the tty structure is not completely set up when this call is made. |
| 954 | */ |
| 955 | |
| 956 | void tty_ldisc_init(struct tty_struct *tty) |
| 957 | { |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 958 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
| 959 | if (IS_ERR(ld)) |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 960 | panic("n_tty: init_tty"); |
Alan Cox | c65c9bc | 2009-06-11 12:50:12 +0100 | [diff] [blame] | 961 | tty_ldisc_assign(tty, ld); |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 962 | } |
| 963 | |
Jiri Slaby | 6716671 | 2011-03-23 10:48:35 +0100 | [diff] [blame] | 964 | /** |
| 965 | * tty_ldisc_init - ldisc cleanup for new tty |
| 966 | * @tty: tty that was allocated recently |
| 967 | * |
| 968 | * The tty structure must not becompletely set up (tty_ldisc_setup) when |
| 969 | * this call is made. |
| 970 | */ |
| 971 | void tty_ldisc_deinit(struct tty_struct *tty) |
| 972 | { |
| 973 | put_ldisc(tty->ldisc); |
| 974 | tty_ldisc_assign(tty, NULL); |
| 975 | } |
| 976 | |
Alan Cox | 01e1abb | 2008-07-22 11:16:55 +0100 | [diff] [blame] | 977 | void tty_ldisc_begin(void) |
| 978 | { |
| 979 | /* Setup the default TTY line discipline. */ |
| 980 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); |
| 981 | } |