include/linux/wait.h

   1 #ifndef _LINUX_WAIT_H
   2 #define _LINUX_WAIT_H
   3 /*
   4  * Linux wait queue related types and methods
   5  */
   6 #include <linux/list.h>
   7 #include <linux/stddef.h>
   8 #include <linux/spinlock.h>
   9 #include <asm/current.h>
  10 #include <uapi/linux/wait.h>
  11
  12 typedef struct __wait_queue wait_queue_t;
  13 typedef int (*wait_queue_func_t)(wait_queue_t *wait, unsigned mode, int flags, void *key);
  14 int default_wake_function(wait_queue_t *wait, unsigned mode, int flags, void *key);
  15
  16 /* __wait_queue::flags */
  17 #define WQ_FLAG_EXCLUSIVE       0x01
  18 #define WQ_FLAG_WOKEN           0x02
  19
  20 struct __wait_queue {
  21         unsigned int            flags;
  22         void                    *private;
  23         wait_queue_func_t       func;
  24         struct list_head        task_list;
  25 };
  26
  27 struct wait_bit_key {
  28         void                    *flags;
  29         int                     bit_nr;
  30 #define WAIT_ATOMIC_T_BIT_NR    -1
  31         unsigned long           timeout;
  32 };
  33
  34 struct wait_bit_queue {
  35         struct wait_bit_key     key;
  36         wait_queue_t            wait;
  37 };
  38
  39 struct __wait_queue_head {
  40         spinlock_t              lock;
  41         struct list_head        task_list;
  42 };
  43 typedef struct __wait_queue_head wait_queue_head_t;
  44
  45 struct task_struct;
  46
  47 /*
  48  * Macros for declaration and initialisaton of the datatypes
  49  */
  50
  51 #define __WAITQUEUE_INITIALIZER(name, tsk) {                            \
  52         .private        = tsk,                                          \
  53         .func           = default_wake_function,                        \
  54         .task_list      = { NULL, NULL } }
  55
  56 #define DECLARE_WAITQUEUE(name, tsk)                                    \
  57         wait_queue_t name = __WAITQUEUE_INITIALIZER(name, tsk)
  58
  59 #define __WAIT_QUEUE_HEAD_INITIALIZER(name) {                           \
  60         .lock           = __SPIN_LOCK_UNLOCKED(name.lock),              \
  61         .task_list      = { &(name).task_list, &(name).task_list } }
  62
  63 #define DECLARE_WAIT_QUEUE_HEAD(name) \
  64         wait_queue_head_t name = __WAIT_QUEUE_HEAD_INITIALIZER(name)
  65
  66 #define __WAIT_BIT_KEY_INITIALIZER(word, bit)                           \
  67         { .flags = word, .bit_nr = bit, }
  68
  69 #define __WAIT_ATOMIC_T_KEY_INITIALIZER(p)                              \
  70         { .flags = p, .bit_nr = WAIT_ATOMIC_T_BIT_NR, }
  71
  72 extern void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *);
  73
  74 #define init_waitqueue_head(q)                          \
  75         do {                                            \
  76                 static struct lock_class_key __key;     \
  77                                                         \
  78                 __init_waitqueue_head((q), #q, &__key); \
  79         } while (0)
  80
  81 #ifdef CONFIG_LOCKDEP
  82 # define __WAIT_QUEUE_HEAD_INIT_ONSTACK(name) \
  83         ({ init_waitqueue_head(&name); name; })
  84 # define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) \
  85         wait_queue_head_t name = __WAIT_QUEUE_HEAD_INIT_ONSTACK(name)
  86 #else
  87 # define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) DECLARE_WAIT_QUEUE_HEAD(name)
  88 #endif
  89
  90 static inline void init_waitqueue_entry(wait_queue_t *q, struct task_struct *p)
  91 {
  92         q->flags        = 0;
  93         q->private      = p;
  94         q->func         = default_wake_function;
  95 }
  96
  97 static inline void
  98 init_waitqueue_func_entry(wait_queue_t *q, wait_queue_func_t func)
  99 {
 100         q->flags        = 0;
 101         q->private      = NULL;
 102         q->func         = func;
 103 }
 104
 105 /**
 106  * waitqueue_active -- locklessly test for waiters on the queue
 107  * @q: the waitqueue to test for waiters
 108  *
 109  * returns true if the wait list is not empty
 110  *
 111  * NOTE: this function is lockless and requires care, incorrect usage _will_
 112  * lead to sporadic and non-obvious failure.
 113  *
 114  * Use either while holding wait_queue_head_t::lock or when used for wakeups
 115  * with an extra smp_mb() like:
 116  *
 117  *      CPU0 - waker                    CPU1 - waiter
 118  *
 119  *                                      for (;;) {
 120  *      @cond = true;                     prepare_to_wait(&wq, &wait, state);
 121  *      smp_mb();                         // smp_mb() from set_current_state()
 122  *      if (waitqueue_active(wq))         if (@cond)
 123  *        wake_up(wq);                      break;
 124  *                                        schedule();
 125  *                                      }
 126  *                                      finish_wait(&wq, &wait);
 127  *
 128  * Because without the explicit smp_mb() it's possible for the
 129  * waitqueue_active() load to get hoisted over the @cond store such that we'll
 130  * observe an empty wait list while the waiter might not observe @cond.
 131  *
 132  * Also note that this 'optimization' trades a spin_lock() for an smp_mb(),
 133  * which (when the lock is uncontended) are of roughly equal cost.
 134  */
 135 static inline int waitqueue_active(wait_queue_head_t *q)
 136 {
 137         return !list_empty(&q->task_list);
 138 }
 139
 140 /**
 141  * wq_has_sleeper - check if there are any waiting processes
 142  * @wq: wait queue head
 143  *
 144  * Returns true if wq has waiting processes
 145  *
 146  * Please refer to the comment for waitqueue_active.
 147  */
 148 static inline bool wq_has_sleeper(wait_queue_head_t *wq)
 149 {
 150         /*
 151          * We need to be sure we are in sync with the
 152          * add_wait_queue modifications to the wait queue.
 153          *
 154          * This memory barrier should be paired with one on the
 155          * waiting side.
 156          */
 157         smp_mb();
 158         return waitqueue_active(wq);
 159 }
 160
 161 extern void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
 162 extern void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait);
 163 extern void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
 164
 165 static inline void __add_wait_queue(wait_queue_head_t *head, wait_queue_t *new)
 166 {
 167         list_add(&new->task_list, &head->task_list);
 168 }
 169
 170 /*
 171  * Used for wake-one threads:
 172  */
 173 static inline void
 174 __add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
 175 {
 176         wait->flags |= WQ_FLAG_EXCLUSIVE;
 177         __add_wait_queue(q, wait);
 178 }
 179
 180 static inline void __add_wait_queue_tail(wait_queue_head_t *head,
 181                                          wait_queue_t *new)
 182 {
 183         list_add_tail(&new->task_list, &head->task_list);
 184 }
 185
 186 static inline void
 187 __add_wait_queue_tail_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
 188 {
 189         wait->flags |= WQ_FLAG_EXCLUSIVE;
 190         __add_wait_queue_tail(q, wait);
 191 }
 192
 193 static inline void
 194 __remove_wait_queue(wait_queue_head_t *head, wait_queue_t *old)
 195 {
 196         list_del(&old->task_list);
 197 }
 198
 199 typedef int wait_bit_action_f(struct wait_bit_key *, int mode);
 200 void __wake_up(wait_queue_head_t *q, unsigned int mode, int nr, void *key);
 201 void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key);
 202 void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode, int nr, void *key);
 203 void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr);
 204 void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr);
 205 void __wake_up_bit(wait_queue_head_t *, void *, int);
 206 int __wait_on_bit(wait_queue_head_t *, struct wait_bit_queue *, wait_bit_action_f *, unsigned);
 207 int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, wait_bit_action_f *, unsigned);
 208 void wake_up_bit(void *, int);
 209 void wake_up_atomic_t(atomic_t *);
 210 int out_of_line_wait_on_bit(void *, int, wait_bit_action_f *, unsigned);
 211 int out_of_line_wait_on_bit_timeout(void *, int, wait_bit_action_f *, unsigned, unsigned long);
 212 int out_of_line_wait_on_bit_lock(void *, int, wait_bit_action_f *, unsigned);
 213 int out_of_line_wait_on_atomic_t(atomic_t *, int (*)(atomic_t *), unsigned);
 214 wait_queue_head_t *bit_waitqueue(void *, int);
 215
 216 #define wake_up(x)                      __wake_up(x, TASK_NORMAL, 1, NULL)
 217 #define wake_up_nr(x, nr)               __wake_up(x, TASK_NORMAL, nr, NULL)
 218 #define wake_up_all(x)                  __wake_up(x, TASK_NORMAL, 0, NULL)
 219 #define wake_up_locked(x)               __wake_up_locked((x), TASK_NORMAL, 1)
 220 #define wake_up_all_locked(x)           __wake_up_locked((x), TASK_NORMAL, 0)
 221
 222 #define wake_up_interruptible(x)        __wake_up(x, TASK_INTERRUPTIBLE, 1, NULL)
 223 #define wake_up_interruptible_nr(x, nr) __wake_up(x, TASK_INTERRUPTIBLE, nr, NULL)
 224 #define wake_up_interruptible_all(x)    __wake_up(x, TASK_INTERRUPTIBLE, 0, NULL)
 225 #define wake_up_interruptible_sync(x)   __wake_up_sync((x), TASK_INTERRUPTIBLE, 1)
 226
 227 /*
 228  * Wakeup macros to be used to report events to the targets.
 229  */
 230 #define wake_up_poll(x, m)                                              \
 231         __wake_up(x, TASK_NORMAL, 1, (void *) (m))
 232 #define wake_up_locked_poll(x, m)                                       \
 233         __wake_up_locked_key((x), TASK_NORMAL, (void *) (m))
 234 #define wake_up_interruptible_poll(x, m)                                \
 235         __wake_up(x, TASK_INTERRUPTIBLE, 1, (void *) (m))
 236 #define wake_up_interruptible_sync_poll(x, m)                           \
 237         __wake_up_sync_key((x), TASK_INTERRUPTIBLE, 1, (void *) (m))
 238
 239 #define ___wait_cond_timeout(condition)                                 \
 240 ({                                                                      \
 241         bool __cond = (condition);                                      \
 242         if (__cond && !__ret)                                           \
 243                 __ret = 1;                                              \
 244         __cond || !__ret;                                               \
 245 })
 246
 247 #define ___wait_is_interruptible(state)                                 \
 248         (!__builtin_constant_p(state) ||                                \
 249                 state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)  \
 250
 251 /*
 252  * The below macro ___wait_event() has an explicit shadow of the __ret
 253  * variable when used from the wait_event_*() macros.
 254  *
 255  * This is so that both can use the ___wait_cond_timeout() construct
 256  * to wrap the condition.
 257  *
 258  * The type inconsistency of the wait_event_*() __ret variable is also
 259  * on purpose; we use long where we can return timeout values and int
 260  * otherwise.
 261  */
 262
 263 #define ___wait_event(wq, condition, state, exclusive, ret, cmd)        \
 264 ({                                                                      \
 265         __label__ __out;                                                \
 266         wait_queue_t __wait;                                            \
 267         long __ret = ret;       /* explicit shadow */                   \
 268                                                                         \
 269         INIT_LIST_HEAD(&__wait.task_list);                              \
 270         if (exclusive)                                                  \
 271                 __wait.flags = WQ_FLAG_EXCLUSIVE;                       \
 272         else                                                            \
 273                 __wait.flags = 0;                                       \
 274                                                                         \
 275         for (;;) {                                                      \
 276                 long __int = prepare_to_wait_event(&wq, &__wait, state);\
 277                                                                         \
 278                 if (condition)                                          \
 279                         break;                                          \
 280                                                                         \
 281                 if (___wait_is_interruptible(state) && __int) {         \
 282                         __ret = __int;                                  \
 283                         if (exclusive) {                                \
 284                                 abort_exclusive_wait(&wq, &__wait,      \
 285                                                      state, NULL);      \
 286                                 goto __out;                             \
 287                         }                                               \
 288                         break;                                          \
 289                 }                                                       \
 290                                                                         \
 291                 cmd;                                                    \
 292         }                                                               \
 293         finish_wait(&wq, &__wait);                                      \
 294 __out:  __ret;                                                          \
 295 })
 296
 297 #define __wait_event(wq, condition)                                     \
 298         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 299                             schedule())
 300
 301 /**
 302  * wait_event - sleep until a condition gets true
 303  * @wq: the waitqueue to wait on
 304  * @condition: a C expression for the event to wait for
 305  *
 306  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 307  * @condition evaluates to true. The @condition is checked each time
 308  * the waitqueue @wq is woken up.
 309  *
 310  * wake_up() has to be called after changing any variable that could
 311  * change the result of the wait condition.
 312  */
 313 #define wait_event(wq, condition)                                       \
 314 do {                                                                    \
 315         might_sleep();                                                  \
 316         if (condition)                                                  \
 317                 break;                                                  \
 318         __wait_event(wq, condition);                                    \
 319 } while (0)
 320
 321 #define __io_wait_event(wq, condition)                                  \
 322         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 323                             io_schedule())
 324
 325 /*
 326  * io_wait_event() -- like wait_event() but with io_schedule()
 327  */
 328 #define io_wait_event(wq, condition)                                    \
 329 do {                                                                    \
 330         might_sleep();                                                  \
 331         if (condition)                                                  \
 332                 break;                                                  \
 333         __io_wait_event(wq, condition);                                 \
 334 } while (0)
 335
 336 #define __wait_event_freezable(wq, condition)                           \
 337         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 338                             schedule(); try_to_freeze())
 339
 340 /**
 341  * wait_event_freezable - sleep (or freeze) until a condition gets true
 342  * @wq: the waitqueue to wait on
 343  * @condition: a C expression for the event to wait for
 344  *
 345  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
 346  * to system load) until the @condition evaluates to true. The
 347  * @condition is checked each time the waitqueue @wq is woken up.
 348  *
 349  * wake_up() has to be called after changing any variable that could
 350  * change the result of the wait condition.
 351  */
 352 #define wait_event_freezable(wq, condition)                             \
 353 ({                                                                      \
 354         int __ret = 0;                                                  \
 355         might_sleep();                                                  \
 356         if (!(condition))                                               \
 357                 __ret = __wait_event_freezable(wq, condition);          \
 358         __ret;                                                          \
 359 })
 360
 361 #define __wait_event_timeout(wq, condition, timeout)                    \
 362         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 363                       TASK_UNINTERRUPTIBLE, 0, timeout,                 \
 364                       __ret = schedule_timeout(__ret))
 365
 366 /**
 367  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
 368  * @wq: the waitqueue to wait on
 369  * @condition: a C expression for the event to wait for
 370  * @timeout: timeout, in jiffies
 371  *
 372  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 373  * @condition evaluates to true. The @condition is checked each time
 374  * the waitqueue @wq is woken up.
 375  *
 376  * wake_up() has to be called after changing any variable that could
 377  * change the result of the wait condition.
 378  *
 379  * Returns:
 380  * 0 if the @condition evaluated to %false after the @timeout elapsed,
 381  * 1 if the @condition evaluated to %true after the @timeout elapsed,
 382  * or the remaining jiffies (at least 1) if the @condition evaluated
 383  * to %true before the @timeout elapsed.
 384  */
 385 #define wait_event_timeout(wq, condition, timeout)                      \
 386 ({                                                                      \
 387         long __ret = timeout;                                           \
 388         might_sleep();                                                  \
 389         if (!___wait_cond_timeout(condition))                           \
 390                 __ret = __wait_event_timeout(wq, condition, timeout);   \
 391         __ret;                                                          \
 392 })
 393
 394 #define __wait_event_freezable_timeout(wq, condition, timeout)          \
 395         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 396                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 397                       __ret = schedule_timeout(__ret); try_to_freeze())
 398
 399 /*
 400  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
 401  * increasing load and is freezable.
 402  */
 403 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 404 ({                                                                      \
 405         long __ret = timeout;                                           \
 406         might_sleep();                                                  \
 407         if (!___wait_cond_timeout(condition))                           \
 408                 __ret = __wait_event_freezable_timeout(wq, condition, timeout); \
 409         __ret;                                                          \
 410 })
 411
 412 #define __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2)           \
 413         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 1, 0,  \
 414                             cmd1; schedule(); cmd2)
 415 /*
 416  * Just like wait_event_cmd(), except it sets exclusive flag
 417  */
 418 #define wait_event_exclusive_cmd(wq, condition, cmd1, cmd2)             \
 419 do {                                                                    \
 420         if (condition)                                                  \
 421                 break;                                                  \
 422         __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2);          \
 423 } while (0)
 424
 425 #define __wait_event_cmd(wq, condition, cmd1, cmd2)                     \
 426         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 427                             cmd1; schedule(); cmd2)
 428
 429 /**
 430  * wait_event_cmd - sleep until a condition gets true
 431  * @wq: the waitqueue to wait on
 432  * @condition: a C expression for the event to wait for
 433  * @cmd1: the command will be executed before sleep
 434  * @cmd2: the command will be executed after sleep
 435  *
 436  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 437  * @condition evaluates to true. The @condition is checked each time
 438  * the waitqueue @wq is woken up.
 439  *
 440  * wake_up() has to be called after changing any variable that could
 441  * change the result of the wait condition.
 442  */
 443 #define wait_event_cmd(wq, condition, cmd1, cmd2)                       \
 444 do {                                                                    \
 445         if (condition)                                                  \
 446                 break;                                                  \
 447         __wait_event_cmd(wq, condition, cmd1, cmd2);                    \
 448 } while (0)
 449
 450 #define __wait_event_interruptible(wq, condition)                       \
 451         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 452                       schedule())
 453
 454 /**
 455  * wait_event_interruptible - sleep until a condition gets true
 456  * @wq: the waitqueue to wait on
 457  * @condition: a C expression for the event to wait for
 458  *
 459  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 460  * @condition evaluates to true or a signal is received.
 461  * The @condition is checked each time the waitqueue @wq is woken up.
 462  *
 463  * wake_up() has to be called after changing any variable that could
 464  * change the result of the wait condition.
 465  *
 466  * The function will return -ERESTARTSYS if it was interrupted by a
 467  * signal and 0 if @condition evaluated to true.
 468  */
 469 #define wait_event_interruptible(wq, condition)                         \
 470 ({                                                                      \
 471         int __ret = 0;                                                  \
 472         might_sleep();                                                  \
 473         if (!(condition))                                               \
 474                 __ret = __wait_event_interruptible(wq, condition);      \
 475         __ret;                                                          \
 476 })
 477
 478 #define __wait_event_interruptible_timeout(wq, condition, timeout)      \
 479         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 480                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 481                       __ret = schedule_timeout(__ret))
 482
 483 /**
 484  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
 485  * @wq: the waitqueue to wait on
 486  * @condition: a C expression for the event to wait for
 487  * @timeout: timeout, in jiffies
 488  *
 489  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 490  * @condition evaluates to true or a signal is received.
 491  * The @condition is checked each time the waitqueue @wq is woken up.
 492  *
 493  * wake_up() has to be called after changing any variable that could
 494  * change the result of the wait condition.
 495  *
 496  * Returns:
 497  * 0 if the @condition evaluated to %false after the @timeout elapsed,
 498  * 1 if the @condition evaluated to %true after the @timeout elapsed,
 499  * the remaining jiffies (at least 1) if the @condition evaluated
 500  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
 501  * interrupted by a signal.
 502  */
 503 #define wait_event_interruptible_timeout(wq, condition, timeout)        \
 504 ({                                                                      \
 505         long __ret = timeout;                                           \
 506         might_sleep();                                                  \
 507         if (!___wait_cond_timeout(condition))                           \
 508                 __ret = __wait_event_interruptible_timeout(wq,          \
 509                                                 condition, timeout);    \
 510         __ret;                                                          \
 511 })
 512
 513 #define __wait_event_hrtimeout(wq, condition, timeout, state)           \
 514 ({                                                                      \
 515         int __ret = 0;                                                  \
 516         struct hrtimer_sleeper __t;                                     \
 517                                                                         \
 518         hrtimer_init_on_stack(&__t.timer, CLOCK_MONOTONIC,              \
 519                               HRTIMER_MODE_REL);                        \
 520         hrtimer_init_sleeper(&__t, current);                            \
 521         if ((timeout).tv64 != KTIME_MAX)                                \
 522                 hrtimer_start_range_ns(&__t.timer, timeout,             \
 523                                        current->timer_slack_ns,         \
 524                                        HRTIMER_MODE_REL);               \
 525                                                                         \
 526         __ret = ___wait_event(wq, condition, state, 0, 0,               \
 527                 if (!__t.task) {                                        \
 528                         __ret = -ETIME;                                 \
 529                         break;                                          \
 530                 }                                                       \
 531                 schedule());                                            \
 532                                                                         \
 533         hrtimer_cancel(&__t.timer);                                     \
 534         destroy_hrtimer_on_stack(&__t.timer);                           \
 535         __ret;                                                          \
 536 })
 537
 538 /**
 539  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
 540  * @wq: the waitqueue to wait on
 541  * @condition: a C expression for the event to wait for
 542  * @timeout: timeout, as a ktime_t
 543  *
 544  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 545  * @condition evaluates to true or a signal is received.
 546  * The @condition is checked each time the waitqueue @wq is woken up.
 547  *
 548  * wake_up() has to be called after changing any variable that could
 549  * change the result of the wait condition.
 550  *
 551  * The function returns 0 if @condition became true, or -ETIME if the timeout
 552  * elapsed.
 553  */
 554 #define wait_event_hrtimeout(wq, condition, timeout)                    \
 555 ({                                                                      \
 556         int __ret = 0;                                                  \
 557         might_sleep();                                                  \
 558         if (!(condition))                                               \
 559                 __ret = __wait_event_hrtimeout(wq, condition, timeout,  \
 560                                                TASK_UNINTERRUPTIBLE);   \
 561         __ret;                                                          \
 562 })
 563
 564 /**
 565  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
 566  * @wq: the waitqueue to wait on
 567  * @condition: a C expression for the event to wait for
 568  * @timeout: timeout, as a ktime_t
 569  *
 570  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 571  * @condition evaluates to true or a signal is received.
 572  * The @condition is checked each time the waitqueue @wq is woken up.
 573  *
 574  * wake_up() has to be called after changing any variable that could
 575  * change the result of the wait condition.
 576  *
 577  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
 578  * interrupted by a signal, or -ETIME if the timeout elapsed.
 579  */
 580 #define wait_event_interruptible_hrtimeout(wq, condition, timeout)      \
 581 ({                                                                      \
 582         long __ret = 0;                                                 \
 583         might_sleep();                                                  \
 584         if (!(condition))                                               \
 585                 __ret = __wait_event_hrtimeout(wq, condition, timeout,  \
 586                                                TASK_INTERRUPTIBLE);     \
 587         __ret;                                                          \
 588 })
 589
 590 #define __wait_event_interruptible_exclusive(wq, condition)             \
 591         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,          \
 592                       schedule())
 593
 594 #define wait_event_interruptible_exclusive(wq, condition)               \
 595 ({                                                                      \
 596         int __ret = 0;                                                  \
 597         might_sleep();                                                  \
 598         if (!(condition))                                               \
 599                 __ret = __wait_event_interruptible_exclusive(wq, condition);\
 600         __ret;                                                          \
 601 })
 602
 603
 604 #define __wait_event_freezable_exclusive(wq, condition)                 \
 605         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,          \
 606                         schedule(); try_to_freeze())
 607
 608 #define wait_event_freezable_exclusive(wq, condition)                   \
 609 ({                                                                      \
 610         int __ret = 0;                                                  \
 611         might_sleep();                                                  \
 612         if (!(condition))                                               \
 613                 __ret = __wait_event_freezable_exclusive(wq, condition);\
 614         __ret;                                                          \
 615 })
 616
 617
 618 #define __wait_event_interruptible_locked(wq, condition, exclusive, irq) \
 619 ({                                                                      \
 620         int __ret = 0;                                                  \
 621         DEFINE_WAIT(__wait);                                            \
 622         if (exclusive)                                                  \
 623                 __wait.flags |= WQ_FLAG_EXCLUSIVE;                      \
 624         do {                                                            \
 625                 if (likely(list_empty(&__wait.task_list)))              \
 626                         __add_wait_queue_tail(&(wq), &__wait);          \
 627                 set_current_state(TASK_INTERRUPTIBLE);                  \
 628                 if (signal_pending(current)) {                          \
 629                         __ret = -ERESTARTSYS;                           \
 630                         break;                                          \
 631                 }                                                       \
 632                 if (irq)                                                \
 633                         spin_unlock_irq(&(wq).lock);                    \
 634                 else                                                    \
 635                         spin_unlock(&(wq).lock);                        \
 636                 schedule();                                             \
 637                 if (irq)                                                \
 638                         spin_lock_irq(&(wq).lock);                      \
 639                 else                                                    \
 640                         spin_lock(&(wq).lock);                          \
 641         } while (!(condition));                                         \
 642         __remove_wait_queue(&(wq), &__wait);                            \
 643         __set_current_state(TASK_RUNNING);                              \
 644         __ret;                                                          \
 645 })
 646
 647
 648 /**
 649  * wait_event_interruptible_locked - sleep until a condition gets true
 650  * @wq: the waitqueue to wait on
 651  * @condition: a C expression for the event to wait for
 652  *
 653  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 654  * @condition evaluates to true or a signal is received.
 655  * The @condition is checked each time the waitqueue @wq is woken up.
 656  *
 657  * It must be called with wq.lock being held.  This spinlock is
 658  * unlocked while sleeping but @condition testing is done while lock
 659  * is held and when this macro exits the lock is held.
 660  *
 661  * The lock is locked/unlocked using spin_lock()/spin_unlock()
 662  * functions which must match the way they are locked/unlocked outside
 663  * of this macro.
 664  *
 665  * wake_up_locked() has to be called after changing any variable that could
 666  * change the result of the wait condition.
 667  *
 668  * The function will return -ERESTARTSYS if it was interrupted by a
 669  * signal and 0 if @condition evaluated to true.
 670  */
 671 #define wait_event_interruptible_locked(wq, condition)                  \
 672         ((condition)                                                    \
 673          ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 0))
 674
 675 /**
 676  * wait_event_interruptible_locked_irq - sleep until a condition gets true
 677  * @wq: the waitqueue to wait on
 678  * @condition: a C expression for the event to wait for
 679  *
 680  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 681  * @condition evaluates to true or a signal is received.
 682  * The @condition is checked each time the waitqueue @wq is woken up.
 683  *
 684  * It must be called with wq.lock being held.  This spinlock is
 685  * unlocked while sleeping but @condition testing is done while lock
 686  * is held and when this macro exits the lock is held.
 687  *
 688  * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()
 689  * functions which must match the way they are locked/unlocked outside
 690  * of this macro.
 691  *
 692  * wake_up_locked() has to be called after changing any variable that could
 693  * change the result of the wait condition.
 694  *
 695  * The function will return -ERESTARTSYS if it was interrupted by a
 696  * signal and 0 if @condition evaluated to true.
 697  */
 698 #define wait_event_interruptible_locked_irq(wq, condition)              \
 699         ((condition)                                                    \
 700          ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 1))
 701
 702 /**
 703  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
 704  * @wq: the waitqueue to wait on
 705  * @condition: a C expression for the event to wait for
 706  *
 707  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 708  * @condition evaluates to true or a signal is received.
 709  * The @condition is checked each time the waitqueue @wq is woken up.
 710  *
 711  * It must be called with wq.lock being held.  This spinlock is
 712  * unlocked while sleeping but @condition testing is done while lock
 713  * is held and when this macro exits the lock is held.
 714  *
 715  * The lock is locked/unlocked using spin_lock()/spin_unlock()
 716  * functions which must match the way they are locked/unlocked outside
 717  * of this macro.
 718  *
 719  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
 720  * set thus when other process waits process on the list if this
 721  * process is awaken further processes are not considered.
 722  *
 723  * wake_up_locked() has to be called after changing any variable that could
 724  * change the result of the wait condition.
 725  *
 726  * The function will return -ERESTARTSYS if it was interrupted by a
 727  * signal and 0 if @condition evaluated to true.
 728  */
 729 #define wait_event_interruptible_exclusive_locked(wq, condition)        \
 730         ((condition)                                                    \
 731          ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 0))
 732
 733 /**
 734  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
 735  * @wq: the waitqueue to wait on
 736  * @condition: a C expression for the event to wait for
 737  *
 738  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 739  * @condition evaluates to true or a signal is received.
 740  * The @condition is checked each time the waitqueue @wq is woken up.
 741  *
 742  * It must be called with wq.lock being held.  This spinlock is
 743  * unlocked while sleeping but @condition testing is done while lock
 744  * is held and when this macro exits the lock is held.
 745  *
 746  * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()
 747  * functions which must match the way they are locked/unlocked outside
 748  * of this macro.
 749  *
 750  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
 751  * set thus when other process waits process on the list if this
 752  * process is awaken further processes are not considered.
 753  *
 754  * wake_up_locked() has to be called after changing any variable that could
 755  * change the result of the wait condition.
 756  *
 757  * The function will return -ERESTARTSYS if it was interrupted by a
 758  * signal and 0 if @condition evaluated to true.
 759  */
 760 #define wait_event_interruptible_exclusive_locked_irq(wq, condition)    \
 761         ((condition)                                                    \
 762          ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 1))
 763
 764
 765 #define __wait_event_killable(wq, condition)                            \
 766         ___wait_event(wq, condition, TASK_KILLABLE, 0, 0, schedule())
 767
 768 /**
 769  * wait_event_killable - sleep until a condition gets true
 770  * @wq: the waitqueue to wait on
 771  * @condition: a C expression for the event to wait for
 772  *
 773  * The process is put to sleep (TASK_KILLABLE) until the
 774  * @condition evaluates to true or a signal is received.
 775  * The @condition is checked each time the waitqueue @wq is woken up.
 776  *
 777  * wake_up() has to be called after changing any variable that could
 778  * change the result of the wait condition.
 779  *
 780  * The function will return -ERESTARTSYS if it was interrupted by a
 781  * signal and 0 if @condition evaluated to true.
 782  */
 783 #define wait_event_killable(wq, condition)                              \
 784 ({                                                                      \
 785         int __ret = 0;                                                  \
 786         might_sleep();                                                  \
 787         if (!(condition))                                               \
 788                 __ret = __wait_event_killable(wq, condition);           \
 789         __ret;                                                          \
 790 })
 791
 792
 793 #define __wait_event_lock_irq(wq, condition, lock, cmd)                 \
 794         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 795                             spin_unlock_irq(&lock);                     \
 796                             cmd;                                        \
 797                             schedule();                                 \
 798                             spin_lock_irq(&lock))
 799
 800 /**
 801  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
 802  *                           condition is checked under the lock. This
 803  *                           is expected to be called with the lock
 804  *                           taken.
 805  * @wq: the waitqueue to wait on
 806  * @condition: a C expression for the event to wait for
 807  * @lock: a locked spinlock_t, which will be released before cmd
 808  *        and schedule() and reacquired afterwards.
 809  * @cmd: a command which is invoked outside the critical section before
 810  *       sleep
 811  *
 812  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 813  * @condition evaluates to true. The @condition is checked each time
 814  * the waitqueue @wq is woken up.
 815  *
 816  * wake_up() has to be called after changing any variable that could
 817  * change the result of the wait condition.
 818  *
 819  * This is supposed to be called while holding the lock. The lock is
 820  * dropped before invoking the cmd and going to sleep and is reacquired
 821  * afterwards.
 822  */
 823 #define wait_event_lock_irq_cmd(wq, condition, lock, cmd)               \
 824 do {                                                                    \
 825         if (condition)                                                  \
 826                 break;                                                  \
 827         __wait_event_lock_irq(wq, condition, lock, cmd);                \
 828 } while (0)
 829
 830 /**
 831  * wait_event_lock_irq - sleep until a condition gets true. The
 832  *                       condition is checked under the lock. This
 833  *                       is expected to be called with the lock
 834  *                       taken.
 835  * @wq: the waitqueue to wait on
 836  * @condition: a C expression for the event to wait for
 837  * @lock: a locked spinlock_t, which will be released before schedule()
 838  *        and reacquired afterwards.
 839  *
 840  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 841  * @condition evaluates to true. The @condition is checked each time
 842  * the waitqueue @wq is woken up.
 843  *
 844  * wake_up() has to be called after changing any variable that could
 845  * change the result of the wait condition.
 846  *
 847  * This is supposed to be called while holding the lock. The lock is
 848  * dropped before going to sleep and is reacquired afterwards.
 849  */
 850 #define wait_event_lock_irq(wq, condition, lock)                        \
 851 do {                                                                    \
 852         if (condition)                                                  \
 853                 break;                                                  \
 854         __wait_event_lock_irq(wq, condition, lock, );                   \
 855 } while (0)
 856
 857
 858 #define __wait_event_interruptible_lock_irq(wq, condition, lock, cmd)   \
 859         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 860                       spin_unlock_irq(&lock);                           \
 861                       cmd;                                              \
 862                       schedule();                                       \
 863                       spin_lock_irq(&lock))
 864
 865 /**
 866  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
 867  *              The condition is checked under the lock. This is expected to
 868  *              be called with the lock taken.
 869  * @wq: the waitqueue to wait on
 870  * @condition: a C expression for the event to wait for
 871  * @lock: a locked spinlock_t, which will be released before cmd and
 872  *        schedule() and reacquired afterwards.
 873  * @cmd: a command which is invoked outside the critical section before
 874  *       sleep
 875  *
 876  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 877  * @condition evaluates to true or a signal is received. The @condition is
 878  * checked each time the waitqueue @wq is woken up.
 879  *
 880  * wake_up() has to be called after changing any variable that could
 881  * change the result of the wait condition.
 882  *
 883  * This is supposed to be called while holding the lock. The lock is
 884  * dropped before invoking the cmd and going to sleep and is reacquired
 885  * afterwards.
 886  *
 887  * The macro will return -ERESTARTSYS if it was interrupted by a signal
 888  * and 0 if @condition evaluated to true.
 889  */
 890 #define wait_event_interruptible_lock_irq_cmd(wq, condition, lock, cmd) \
 891 ({                                                                      \
 892         int __ret = 0;                                                  \
 893         if (!(condition))                                               \
 894                 __ret = __wait_event_interruptible_lock_irq(wq,         \
 895                                                 condition, lock, cmd);  \
 896         __ret;                                                          \
 897 })
 898
 899 /**
 900  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
 901  *              The condition is checked under the lock. This is expected
 902  *              to be called with the lock taken.
 903  * @wq: the waitqueue to wait on
 904  * @condition: a C expression for the event to wait for
 905  * @lock: a locked spinlock_t, which will be released before schedule()
 906  *        and reacquired afterwards.
 907  *
 908  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 909  * @condition evaluates to true or signal is received. The @condition is
 910  * checked each time the waitqueue @wq is woken up.
 911  *
 912  * wake_up() has to be called after changing any variable that could
 913  * change the result of the wait condition.
 914  *
 915  * This is supposed to be called while holding the lock. The lock is
 916  * dropped before going to sleep and is reacquired afterwards.
 917  *
 918  * The macro will return -ERESTARTSYS if it was interrupted by a signal
 919  * and 0 if @condition evaluated to true.
 920  */
 921 #define wait_event_interruptible_lock_irq(wq, condition, lock)          \
 922 ({                                                                      \
 923         int __ret = 0;                                                  \
 924         if (!(condition))                                               \
 925                 __ret = __wait_event_interruptible_lock_irq(wq,         \
 926                                                 condition, lock,);      \
 927         __ret;                                                          \
 928 })
 929
 930 #define __wait_event_interruptible_lock_irq_timeout(wq, condition,      \
 931                                                     lock, timeout)      \
 932         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 933                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 934                       spin_unlock_irq(&lock);                           \
 935                       __ret = schedule_timeout(__ret);                  \
 936                       spin_lock_irq(&lock));
 937
 938 /**
 939  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
 940  *              true or a timeout elapses. The condition is checked under
 941  *              the lock. This is expected to be called with the lock taken.
 942  * @wq: the waitqueue to wait on
 943  * @condition: a C expression for the event to wait for
 944  * @lock: a locked spinlock_t, which will be released before schedule()
 945  *        and reacquired afterwards.
 946  * @timeout: timeout, in jiffies
 947  *
 948  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 949  * @condition evaluates to true or signal is received. The @condition is
 950  * checked each time the waitqueue @wq is woken up.
 951  *
 952  * wake_up() has to be called after changing any variable that could
 953  * change the result of the wait condition.
 954  *
 955  * This is supposed to be called while holding the lock. The lock is
 956  * dropped before going to sleep and is reacquired afterwards.
 957  *
 958  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
 959  * was interrupted by a signal, and the remaining jiffies otherwise
 960  * if the condition evaluated to true before the timeout elapsed.
 961  */
 962 #define wait_event_interruptible_lock_irq_timeout(wq, condition, lock,  \
 963                                                   timeout)              \
 964 ({                                                                      \
 965         long __ret = timeout;                                           \
 966         if (!___wait_cond_timeout(condition))                           \
 967                 __ret = __wait_event_interruptible_lock_irq_timeout(    \
 968                                         wq, condition, lock, timeout);  \
 969         __ret;                                                          \
 970 })
 971
 972 /*
 973  * Waitqueues which are removed from the waitqueue_head at wakeup time
 974  */
 975 void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
 976 void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
 977 long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
 978 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
 979 void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, unsigned int mode, void *key);
 980 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout);
 981 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 982 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 983 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 984
 985 #define DEFINE_WAIT_FUNC(name, function)                                \
 986         wait_queue_t name = {                                           \
 987                 .private        = current,                              \
 988                 .func           = function,                             \
 989                 .task_list      = LIST_HEAD_INIT((name).task_list),     \
 990         }
 991
 992 #define DEFINE_WAIT(name) DEFINE_WAIT_FUNC(name, autoremove_wake_function)
 993
 994 #define DEFINE_WAIT_BIT(name, word, bit)                                \
 995         struct wait_bit_queue name = {                                  \
 996                 .key = __WAIT_BIT_KEY_INITIALIZER(word, bit),           \
 997                 .wait   = {                                             \
 998                         .private        = current,                      \
 999                         .func           = wake_bit_function,            \
1000                         .task_list      =                               \
1001                                 LIST_HEAD_INIT((name).wait.task_list),  \
1002                 },                                                      \
1003         }
1004
1005 #define init_wait(wait)                                                 \
1006         do {                                                            \
1007                 (wait)->private = current;                              \
1008                 (wait)->func = autoremove_wake_function;                \
1009                 INIT_LIST_HEAD(&(wait)->task_list);                     \
1010                 (wait)->flags = 0;                                      \
1011         } while (0)
1012
1013
1014 extern int bit_wait(struct wait_bit_key *, int);
1015 extern int bit_wait_io(struct wait_bit_key *, int);
1016 extern int bit_wait_timeout(struct wait_bit_key *, int);
1017 extern int bit_wait_io_timeout(struct wait_bit_key *, int);
1018
1019 /**
1020  * wait_on_bit - wait for a bit to be cleared
1021  * @word: the word being waited on, a kernel virtual address
1022  * @bit: the bit of the word being waited on
1023  * @mode: the task state to sleep in
1024  *
1025  * There is a standard hashed waitqueue table for generic use. This
1026  * is the part of the hashtable's accessor API that waits on a bit.
1027  * For instance, if one were to have waiters on a bitflag, one would
1028  * call wait_on_bit() in threads waiting for the bit to clear.
1029  * One uses wait_on_bit() where one is waiting for the bit to clear,
1030  * but has no intention of setting it.
1031  * Returned value will be zero if the bit was cleared, or non-zero
1032  * if the process received a signal and the mode permitted wakeup
1033  * on that signal.
1034  */
1035 static inline int
1036 wait_on_bit(unsigned long *word, int bit, unsigned mode)
1037 {
1038         might_sleep();
1039         if (!test_bit(bit, word))
1040                 return 0;
1041         return out_of_line_wait_on_bit(word, bit,
1042                                        bit_wait,
1043                                        mode);
1044 }
1045
1046 /**
1047  * wait_on_bit_io - wait for a bit to be cleared
1048  * @word: the word being waited on, a kernel virtual address
1049  * @bit: the bit of the word being waited on
1050  * @mode: the task state to sleep in
1051  *
1052  * Use the standard hashed waitqueue table to wait for a bit
1053  * to be cleared.  This is similar to wait_on_bit(), but calls
1054  * io_schedule() instead of schedule() for the actual waiting.
1055  *
1056  * Returned value will be zero if the bit was cleared, or non-zero
1057  * if the process received a signal and the mode permitted wakeup
1058  * on that signal.
1059  */
1060 static inline int
1061 wait_on_bit_io(unsigned long *word, int bit, unsigned mode)
1062 {
1063         might_sleep();
1064         if (!test_bit(bit, word))
1065                 return 0;
1066         return out_of_line_wait_on_bit(word, bit,
1067                                        bit_wait_io,
1068                                        mode);
1069 }
1070
1071 /**
1072  * wait_on_bit_timeout - wait for a bit to be cleared or a timeout elapses
1073  * @word: the word being waited on, a kernel virtual address
1074  * @bit: the bit of the word being waited on
1075  * @mode: the task state to sleep in
1076  * @timeout: timeout, in jiffies
1077  *
1078  * Use the standard hashed waitqueue table to wait for a bit
1079  * to be cleared. This is similar to wait_on_bit(), except also takes a
1080  * timeout parameter.
1081  *
1082  * Returned value will be zero if the bit was cleared before the
1083  * @timeout elapsed, or non-zero if the @timeout elapsed or process
1084  * received a signal and the mode permitted wakeup on that signal.
1085  */
1086 static inline int
1087 wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode,
1088                     unsigned long timeout)
1089 {
1090         might_sleep();
1091         if (!test_bit(bit, word))
1092                 return 0;
1093         return out_of_line_wait_on_bit_timeout(word, bit,
1094                                                bit_wait_timeout,
1095                                                mode, timeout);
1096 }
1097
1098 /**
1099  * wait_on_bit_action - wait for a bit to be cleared
1100  * @word: the word being waited on, a kernel virtual address
1101  * @bit: the bit of the word being waited on
1102  * @action: the function used to sleep, which may take special actions
1103  * @mode: the task state to sleep in
1104  *
1105  * Use the standard hashed waitqueue table to wait for a bit
1106  * to be cleared, and allow the waiting action to be specified.
1107  * This is like wait_on_bit() but allows fine control of how the waiting
1108  * is done.
1109  *
1110  * Returned value will be zero if the bit was cleared, or non-zero
1111  * if the process received a signal and the mode permitted wakeup
1112  * on that signal.
1113  */
1114 static inline int
1115 wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action,
1116                    unsigned mode)
1117 {
1118         might_sleep();
1119         if (!test_bit(bit, word))
1120                 return 0;
1121         return out_of_line_wait_on_bit(word, bit, action, mode);
1122 }
1123
1124 /**
1125  * wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it
1126  * @word: the word being waited on, a kernel virtual address
1127  * @bit: the bit of the word being waited on
1128  * @mode: the task state to sleep in
1129  *
1130  * There is a standard hashed waitqueue table for generic use. This
1131  * is the part of the hashtable's accessor API that waits on a bit
1132  * when one intends to set it, for instance, trying to lock bitflags.
1133  * For instance, if one were to have waiters trying to set bitflag
1134  * and waiting for it to clear before setting it, one would call
1135  * wait_on_bit() in threads waiting to be able to set the bit.
1136  * One uses wait_on_bit_lock() where one is waiting for the bit to
1137  * clear with the intention of setting it, and when done, clearing it.
1138  *
1139  * Returns zero if the bit was (eventually) found to be clear and was
1140  * set.  Returns non-zero if a signal was delivered to the process and
1141  * the @mode allows that signal to wake the process.
1142  */
1143 static inline int
1144 wait_on_bit_lock(unsigned long *word, int bit, unsigned mode)
1145 {
1146         might_sleep();
1147         if (!test_and_set_bit(bit, word))
1148                 return 0;
1149         return out_of_line_wait_on_bit_lock(word, bit, bit_wait, mode);
1150 }
1151
1152 /**
1153  * wait_on_bit_lock_io - wait for a bit to be cleared, when wanting to set it
1154  * @word: the word being waited on, a kernel virtual address
1155  * @bit: the bit of the word being waited on
1156  * @mode: the task state to sleep in
1157  *
1158  * Use the standard hashed waitqueue table to wait for a bit
1159  * to be cleared and then to atomically set it.  This is similar
1160  * to wait_on_bit(), but calls io_schedule() instead of schedule()
1161  * for the actual waiting.
1162  *
1163  * Returns zero if the bit was (eventually) found to be clear and was
1164  * set.  Returns non-zero if a signal was delivered to the process and
1165  * the @mode allows that signal to wake the process.
1166  */
1167 static inline int
1168 wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode)
1169 {
1170         might_sleep();
1171         if (!test_and_set_bit(bit, word))
1172                 return 0;
1173         return out_of_line_wait_on_bit_lock(word, bit, bit_wait_io, mode);
1174 }
1175
1176 /**
1177  * wait_on_bit_lock_action - wait for a bit to be cleared, when wanting to set it
1178  * @word: the word being waited on, a kernel virtual address
1179  * @bit: the bit of the word being waited on
1180  * @action: the function used to sleep, which may take special actions
1181  * @mode: the task state to sleep in
1182  *
1183  * Use the standard hashed waitqueue table to wait for a bit
1184  * to be cleared and then to set it, and allow the waiting action
1185  * to be specified.
1186  * This is like wait_on_bit() but allows fine control of how the waiting
1187  * is done.
1188  *
1189  * Returns zero if the bit was (eventually) found to be clear and was
1190  * set.  Returns non-zero if a signal was delivered to the process and
1191  * the @mode allows that signal to wake the process.
1192  */
1193 static inline int
1194 wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action,
1195                         unsigned mode)
1196 {
1197         might_sleep();
1198         if (!test_and_set_bit(bit, word))
1199                 return 0;
1200         return out_of_line_wait_on_bit_lock(word, bit, action, mode);
1201 }
1202
1203 /**
1204  * wait_on_atomic_t - Wait for an atomic_t to become 0
1205  * @val: The atomic value being waited on, a kernel virtual address
1206  * @action: the function used to sleep, which may take special actions
1207  * @mode: the task state to sleep in
1208  *
1209  * Wait for an atomic_t to become 0.  We abuse the bit-wait waitqueue table for
1210  * the purpose of getting a waitqueue, but we set the key to a bit number
1211  * outside of the target 'word'.
1212  */
1213 static inline
1214 int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
1215 {
1216         might_sleep();
1217         if (atomic_read(val) == 0)
1218                 return 0;
1219         return out_of_line_wait_on_atomic_t(val, action, mode);
1220 }
1221
1222 #endif /* _LINUX_WAIT_H */