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                         goto __out;                                     \
 284                 }                                                       \
 285                                                                         \
 286                 cmd;                                                    \
 287         }                                                               \
 288         finish_wait(&wq, &__wait);                                      \
 289 __out:  __ret;                                                          \
 290 })
 291
 292 #define __wait_event(wq, condition)                                     \
 293         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 294                             schedule())
 295
 296 /**
 297  * wait_event - sleep until a condition gets true
 298  * @wq: the waitqueue to wait on
 299  * @condition: a C expression for the event to wait for
 300  *
 301  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 302  * @condition evaluates to true. The @condition is checked each time
 303  * the waitqueue @wq is woken up.
 304  *
 305  * wake_up() has to be called after changing any variable that could
 306  * change the result of the wait condition.
 307  */
 308 #define wait_event(wq, condition)                                       \
 309 do {                                                                    \
 310         might_sleep();                                                  \
 311         if (condition)                                                  \
 312                 break;                                                  \
 313         __wait_event(wq, condition);                                    \
 314 } while (0)
 315
 316 #define __io_wait_event(wq, condition)                                  \
 317         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 318                             io_schedule())
 319
 320 /*
 321  * io_wait_event() -- like wait_event() but with io_schedule()
 322  */
 323 #define io_wait_event(wq, condition)                                    \
 324 do {                                                                    \
 325         might_sleep();                                                  \
 326         if (condition)                                                  \
 327                 break;                                                  \
 328         __io_wait_event(wq, condition);                                 \
 329 } while (0)
 330
 331 #define __wait_event_freezable(wq, condition)                           \
 332         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 333                             schedule(); try_to_freeze())
 334
 335 /**
 336  * wait_event_freezable - sleep (or freeze) until a condition gets true
 337  * @wq: the waitqueue to wait on
 338  * @condition: a C expression for the event to wait for
 339  *
 340  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
 341  * to system load) until the @condition evaluates to true. The
 342  * @condition is checked each time the waitqueue @wq is woken up.
 343  *
 344  * wake_up() has to be called after changing any variable that could
 345  * change the result of the wait condition.
 346  */
 347 #define wait_event_freezable(wq, condition)                             \
 348 ({                                                                      \
 349         int __ret = 0;                                                  \
 350         might_sleep();                                                  \
 351         if (!(condition))                                               \
 352                 __ret = __wait_event_freezable(wq, condition);          \
 353         __ret;                                                          \
 354 })
 355
 356 #define __wait_event_timeout(wq, condition, timeout)                    \
 357         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 358                       TASK_UNINTERRUPTIBLE, 0, timeout,                 \
 359                       __ret = schedule_timeout(__ret))
 360
 361 /**
 362  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
 363  * @wq: the waitqueue to wait on
 364  * @condition: a C expression for the event to wait for
 365  * @timeout: timeout, in jiffies
 366  *
 367  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 368  * @condition evaluates to true. The @condition is checked each time
 369  * the waitqueue @wq is woken up.
 370  *
 371  * wake_up() has to be called after changing any variable that could
 372  * change the result of the wait condition.
 373  *
 374  * Returns:
 375  * 0 if the @condition evaluated to %false after the @timeout elapsed,
 376  * 1 if the @condition evaluated to %true after the @timeout elapsed,
 377  * or the remaining jiffies (at least 1) if the @condition evaluated
 378  * to %true before the @timeout elapsed.
 379  */
 380 #define wait_event_timeout(wq, condition, timeout)                      \
 381 ({                                                                      \
 382         long __ret = timeout;                                           \
 383         might_sleep();                                                  \
 384         if (!___wait_cond_timeout(condition))                           \
 385                 __ret = __wait_event_timeout(wq, condition, timeout);   \
 386         __ret;                                                          \
 387 })
 388
 389 #define __wait_event_freezable_timeout(wq, condition, timeout)          \
 390         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 391                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 392                       __ret = schedule_timeout(__ret); try_to_freeze())
 393
 394 /*
 395  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
 396  * increasing load and is freezable.
 397  */
 398 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 399 ({                                                                      \
 400         long __ret = timeout;                                           \
 401         might_sleep();                                                  \
 402         if (!___wait_cond_timeout(condition))                           \
 403                 __ret = __wait_event_freezable_timeout(wq, condition, timeout); \
 404         __ret;                                                          \
 405 })
 406
 407 #define __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2)           \
 408         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 1, 0,  \
 409                             cmd1; schedule(); cmd2)
 410 /*
 411  * Just like wait_event_cmd(), except it sets exclusive flag
 412  */
 413 #define wait_event_exclusive_cmd(wq, condition, cmd1, cmd2)             \
 414 do {                                                                    \
 415         if (condition)                                                  \
 416                 break;                                                  \
 417         __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2);          \
 418 } while (0)
 419
 420 #define __wait_event_cmd(wq, condition, cmd1, cmd2)                     \
 421         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 422                             cmd1; schedule(); cmd2)
 423
 424 /**
 425  * wait_event_cmd - sleep until a condition gets true
 426  * @wq: the waitqueue to wait on
 427  * @condition: a C expression for the event to wait for
 428  * @cmd1: the command will be executed before sleep
 429  * @cmd2: the command will be executed after sleep
 430  *
 431  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 432  * @condition evaluates to true. The @condition is checked each time
 433  * the waitqueue @wq is woken up.
 434  *
 435  * wake_up() has to be called after changing any variable that could
 436  * change the result of the wait condition.
 437  */
 438 #define wait_event_cmd(wq, condition, cmd1, cmd2)                       \
 439 do {                                                                    \
 440         if (condition)                                                  \
 441                 break;                                                  \
 442         __wait_event_cmd(wq, condition, cmd1, cmd2);                    \
 443 } while (0)
 444
 445 #define __wait_event_interruptible(wq, condition)                       \
 446         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 447                       schedule())
 448
 449 /**
 450  * wait_event_interruptible - sleep until a condition gets true
 451  * @wq: the waitqueue to wait on
 452  * @condition: a C expression for the event to wait for
 453  *
 454  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 455  * @condition evaluates to true or a signal is received.
 456  * The @condition is checked each time the waitqueue @wq is woken up.
 457  *
 458  * wake_up() has to be called after changing any variable that could
 459  * change the result of the wait condition.
 460  *
 461  * The function will return -ERESTARTSYS if it was interrupted by a
 462  * signal and 0 if @condition evaluated to true.
 463  */
 464 #define wait_event_interruptible(wq, condition)                         \
 465 ({                                                                      \
 466         int __ret = 0;                                                  \
 467         might_sleep();                                                  \
 468         if (!(condition))                                               \
 469                 __ret = __wait_event_interruptible(wq, condition);      \
 470         __ret;                                                          \
 471 })
 472
 473 #define __wait_event_interruptible_timeout(wq, condition, timeout)      \
 474         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 475                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 476                       __ret = schedule_timeout(__ret))
 477
 478 /**
 479  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
 480  * @wq: the waitqueue to wait on
 481  * @condition: a C expression for the event to wait for
 482  * @timeout: timeout, in jiffies
 483  *
 484  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 485  * @condition evaluates to true or a signal is received.
 486  * The @condition is checked each time the waitqueue @wq is woken up.
 487  *
 488  * wake_up() has to be called after changing any variable that could
 489  * change the result of the wait condition.
 490  *
 491  * Returns:
 492  * 0 if the @condition evaluated to %false after the @timeout elapsed,
 493  * 1 if the @condition evaluated to %true after the @timeout elapsed,
 494  * the remaining jiffies (at least 1) if the @condition evaluated
 495  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
 496  * interrupted by a signal.
 497  */
 498 #define wait_event_interruptible_timeout(wq, condition, timeout)        \
 499 ({                                                                      \
 500         long __ret = timeout;                                           \
 501         might_sleep();                                                  \
 502         if (!___wait_cond_timeout(condition))                           \
 503                 __ret = __wait_event_interruptible_timeout(wq,          \
 504                                                 condition, timeout);    \
 505         __ret;                                                          \
 506 })
 507
 508 #define __wait_event_hrtimeout(wq, condition, timeout, state)           \
 509 ({                                                                      \
 510         int __ret = 0;                                                  \
 511         struct hrtimer_sleeper __t;                                     \
 512                                                                         \
 513         hrtimer_init_on_stack(&__t.timer, CLOCK_MONOTONIC,              \
 514                               HRTIMER_MODE_REL);                        \
 515         hrtimer_init_sleeper(&__t, current);                            \
 516         if ((timeout).tv64 != KTIME_MAX)                                \
 517                 hrtimer_start_range_ns(&__t.timer, timeout,             \
 518                                        current->timer_slack_ns,         \
 519                                        HRTIMER_MODE_REL);               \
 520                                                                         \
 521         __ret = ___wait_event(wq, condition, state, 0, 0,               \
 522                 if (!__t.task) {                                        \
 523                         __ret = -ETIME;                                 \
 524                         break;                                          \
 525                 }                                                       \
 526                 schedule());                                            \
 527                                                                         \
 528         hrtimer_cancel(&__t.timer);                                     \
 529         destroy_hrtimer_on_stack(&__t.timer);                           \
 530         __ret;                                                          \
 531 })
 532
 533 /**
 534  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
 535  * @wq: the waitqueue to wait on
 536  * @condition: a C expression for the event to wait for
 537  * @timeout: timeout, as a ktime_t
 538  *
 539  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 540  * @condition evaluates to true or a signal is received.
 541  * The @condition is checked each time the waitqueue @wq is woken up.
 542  *
 543  * wake_up() has to be called after changing any variable that could
 544  * change the result of the wait condition.
 545  *
 546  * The function returns 0 if @condition became true, or -ETIME if the timeout
 547  * elapsed.
 548  */
 549 #define wait_event_hrtimeout(wq, condition, timeout)                    \
 550 ({                                                                      \
 551         int __ret = 0;                                                  \
 552         might_sleep();                                                  \
 553         if (!(condition))                                               \
 554                 __ret = __wait_event_hrtimeout(wq, condition, timeout,  \
 555                                                TASK_UNINTERRUPTIBLE);   \
 556         __ret;                                                          \
 557 })
 558
 559 /**
 560  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
 561  * @wq: the waitqueue to wait on
 562  * @condition: a C expression for the event to wait for
 563  * @timeout: timeout, as a ktime_t
 564  *
 565  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 566  * @condition evaluates to true or a signal is received.
 567  * The @condition is checked each time the waitqueue @wq is woken up.
 568  *
 569  * wake_up() has to be called after changing any variable that could
 570  * change the result of the wait condition.
 571  *
 572  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
 573  * interrupted by a signal, or -ETIME if the timeout elapsed.
 574  */
 575 #define wait_event_interruptible_hrtimeout(wq, condition, timeout)      \
 576 ({                                                                      \
 577         long __ret = 0;                                                 \
 578         might_sleep();                                                  \
 579         if (!(condition))                                               \
 580                 __ret = __wait_event_hrtimeout(wq, condition, timeout,  \
 581                                                TASK_INTERRUPTIBLE);     \
 582         __ret;                                                          \
 583 })
 584
 585 #define __wait_event_interruptible_exclusive(wq, condition)             \
 586         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,          \
 587                       schedule())
 588
 589 #define wait_event_interruptible_exclusive(wq, condition)               \
 590 ({                                                                      \
 591         int __ret = 0;                                                  \
 592         might_sleep();                                                  \
 593         if (!(condition))                                               \
 594                 __ret = __wait_event_interruptible_exclusive(wq, condition);\
 595         __ret;                                                          \
 596 })
 597
 598 #define __wait_event_killable_exclusive(wq, condition)                  \
 599         ___wait_event(wq, condition, TASK_KILLABLE, 1, 0,               \
 600                       schedule())
 601
 602 #define wait_event_killable_exclusive(wq, condition)                    \
 603 ({                                                                      \
 604         int __ret = 0;                                                  \
 605         might_sleep();                                                  \
 606         if (!(condition))                                               \
 607                 __ret = __wait_event_killable_exclusive(wq, condition); \
 608         __ret;                                                          \
 609 })
 610
 611
 612 #define __wait_event_freezable_exclusive(wq, condition)                 \
 613         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,          \
 614                         schedule(); try_to_freeze())
 615
 616 #define wait_event_freezable_exclusive(wq, condition)                   \
 617 ({                                                                      \
 618         int __ret = 0;                                                  \
 619         might_sleep();                                                  \
 620         if (!(condition))                                               \
 621                 __ret = __wait_event_freezable_exclusive(wq, condition);\
 622         __ret;                                                          \
 623 })
 624
 625
 626 #define __wait_event_interruptible_locked(wq, condition, exclusive, irq) \
 627 ({                                                                      \
 628         int __ret = 0;                                                  \
 629         DEFINE_WAIT(__wait);                                            \
 630         if (exclusive)                                                  \
 631                 __wait.flags |= WQ_FLAG_EXCLUSIVE;                      \
 632         do {                                                            \
 633                 if (likely(list_empty(&__wait.task_list)))              \
 634                         __add_wait_queue_tail(&(wq), &__wait);          \
 635                 set_current_state(TASK_INTERRUPTIBLE);                  \
 636                 if (signal_pending(current)) {                          \
 637                         __ret = -ERESTARTSYS;                           \
 638                         break;                                          \
 639                 }                                                       \
 640                 if (irq)                                                \
 641                         spin_unlock_irq(&(wq).lock);                    \
 642                 else                                                    \
 643                         spin_unlock(&(wq).lock);                        \
 644                 schedule();                                             \
 645                 if (irq)                                                \
 646                         spin_lock_irq(&(wq).lock);                      \
 647                 else                                                    \
 648                         spin_lock(&(wq).lock);                          \
 649         } while (!(condition));                                         \
 650         __remove_wait_queue(&(wq), &__wait);                            \
 651         __set_current_state(TASK_RUNNING);                              \
 652         __ret;                                                          \
 653 })
 654
 655
 656 /**
 657  * wait_event_interruptible_locked - sleep until a condition gets true
 658  * @wq: the waitqueue to wait on
 659  * @condition: a C expression for the event to wait for
 660  *
 661  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 662  * @condition evaluates to true or a signal is received.
 663  * The @condition is checked each time the waitqueue @wq is woken up.
 664  *
 665  * It must be called with wq.lock being held.  This spinlock is
 666  * unlocked while sleeping but @condition testing is done while lock
 667  * is held and when this macro exits the lock is held.
 668  *
 669  * The lock is locked/unlocked using spin_lock()/spin_unlock()
 670  * functions which must match the way they are locked/unlocked outside
 671  * of this macro.
 672  *
 673  * wake_up_locked() has to be called after changing any variable that could
 674  * change the result of the wait condition.
 675  *
 676  * The function will return -ERESTARTSYS if it was interrupted by a
 677  * signal and 0 if @condition evaluated to true.
 678  */
 679 #define wait_event_interruptible_locked(wq, condition)                  \
 680         ((condition)                                                    \
 681          ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 0))
 682
 683 /**
 684  * wait_event_interruptible_locked_irq - sleep until a condition gets true
 685  * @wq: the waitqueue to wait on
 686  * @condition: a C expression for the event to wait for
 687  *
 688  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 689  * @condition evaluates to true or a signal is received.
 690  * The @condition is checked each time the waitqueue @wq is woken up.
 691  *
 692  * It must be called with wq.lock being held.  This spinlock is
 693  * unlocked while sleeping but @condition testing is done while lock
 694  * is held and when this macro exits the lock is held.
 695  *
 696  * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()
 697  * functions which must match the way they are locked/unlocked outside
 698  * of this macro.
 699  *
 700  * wake_up_locked() has to be called after changing any variable that could
 701  * change the result of the wait condition.
 702  *
 703  * The function will return -ERESTARTSYS if it was interrupted by a
 704  * signal and 0 if @condition evaluated to true.
 705  */
 706 #define wait_event_interruptible_locked_irq(wq, condition)              \
 707         ((condition)                                                    \
 708          ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 1))
 709
 710 /**
 711  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
 712  * @wq: the waitqueue to wait on
 713  * @condition: a C expression for the event to wait for
 714  *
 715  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 716  * @condition evaluates to true or a signal is received.
 717  * The @condition is checked each time the waitqueue @wq is woken up.
 718  *
 719  * It must be called with wq.lock being held.  This spinlock is
 720  * unlocked while sleeping but @condition testing is done while lock
 721  * is held and when this macro exits the lock is held.
 722  *
 723  * The lock is locked/unlocked using spin_lock()/spin_unlock()
 724  * functions which must match the way they are locked/unlocked outside
 725  * of this macro.
 726  *
 727  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
 728  * set thus when other process waits process on the list if this
 729  * process is awaken further processes are not considered.
 730  *
 731  * wake_up_locked() has to be called after changing any variable that could
 732  * change the result of the wait condition.
 733  *
 734  * The function will return -ERESTARTSYS if it was interrupted by a
 735  * signal and 0 if @condition evaluated to true.
 736  */
 737 #define wait_event_interruptible_exclusive_locked(wq, condition)        \
 738         ((condition)                                                    \
 739          ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 0))
 740
 741 /**
 742  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
 743  * @wq: the waitqueue to wait on
 744  * @condition: a C expression for the event to wait for
 745  *
 746  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 747  * @condition evaluates to true or a signal is received.
 748  * The @condition is checked each time the waitqueue @wq is woken up.
 749  *
 750  * It must be called with wq.lock being held.  This spinlock is
 751  * unlocked while sleeping but @condition testing is done while lock
 752  * is held and when this macro exits the lock is held.
 753  *
 754  * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()
 755  * functions which must match the way they are locked/unlocked outside
 756  * of this macro.
 757  *
 758  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
 759  * set thus when other process waits process on the list if this
 760  * process is awaken further processes are not considered.
 761  *
 762  * wake_up_locked() has to be called after changing any variable that could
 763  * change the result of the wait condition.
 764  *
 765  * The function will return -ERESTARTSYS if it was interrupted by a
 766  * signal and 0 if @condition evaluated to true.
 767  */
 768 #define wait_event_interruptible_exclusive_locked_irq(wq, condition)    \
 769         ((condition)                                                    \
 770          ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 1))
 771
 772
 773 #define __wait_event_killable(wq, condition)                            \
 774         ___wait_event(wq, condition, TASK_KILLABLE, 0, 0, schedule())
 775
 776 /**
 777  * wait_event_killable - sleep until a condition gets true
 778  * @wq: the waitqueue to wait on
 779  * @condition: a C expression for the event to wait for
 780  *
 781  * The process is put to sleep (TASK_KILLABLE) until the
 782  * @condition evaluates to true or a signal is received.
 783  * The @condition is checked each time the waitqueue @wq is woken up.
 784  *
 785  * wake_up() has to be called after changing any variable that could
 786  * change the result of the wait condition.
 787  *
 788  * The function will return -ERESTARTSYS if it was interrupted by a
 789  * signal and 0 if @condition evaluated to true.
 790  */
 791 #define wait_event_killable(wq, condition)                              \
 792 ({                                                                      \
 793         int __ret = 0;                                                  \
 794         might_sleep();                                                  \
 795         if (!(condition))                                               \
 796                 __ret = __wait_event_killable(wq, condition);           \
 797         __ret;                                                          \
 798 })
 799
 800
 801 #define __wait_event_lock_irq(wq, condition, lock, cmd)                 \
 802         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 803                             spin_unlock_irq(&lock);                     \
 804                             cmd;                                        \
 805                             schedule();                                 \
 806                             spin_lock_irq(&lock))
 807
 808 /**
 809  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
 810  *                           condition is checked under the lock. This
 811  *                           is expected to be called with the lock
 812  *                           taken.
 813  * @wq: the waitqueue to wait on
 814  * @condition: a C expression for the event to wait for
 815  * @lock: a locked spinlock_t, which will be released before cmd
 816  *        and schedule() and reacquired afterwards.
 817  * @cmd: a command which is invoked outside the critical section before
 818  *       sleep
 819  *
 820  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 821  * @condition evaluates to true. The @condition is checked each time
 822  * the waitqueue @wq is woken up.
 823  *
 824  * wake_up() has to be called after changing any variable that could
 825  * change the result of the wait condition.
 826  *
 827  * This is supposed to be called while holding the lock. The lock is
 828  * dropped before invoking the cmd and going to sleep and is reacquired
 829  * afterwards.
 830  */
 831 #define wait_event_lock_irq_cmd(wq, condition, lock, cmd)               \
 832 do {                                                                    \
 833         if (condition)                                                  \
 834                 break;                                                  \
 835         __wait_event_lock_irq(wq, condition, lock, cmd);                \
 836 } while (0)
 837
 838 /**
 839  * wait_event_lock_irq - sleep until a condition gets true. The
 840  *                       condition is checked under the lock. This
 841  *                       is expected to be called with the lock
 842  *                       taken.
 843  * @wq: the waitqueue to wait on
 844  * @condition: a C expression for the event to wait for
 845  * @lock: a locked spinlock_t, which will be released before schedule()
 846  *        and reacquired afterwards.
 847  *
 848  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 849  * @condition evaluates to true. The @condition is checked each time
 850  * the waitqueue @wq is woken up.
 851  *
 852  * wake_up() has to be called after changing any variable that could
 853  * change the result of the wait condition.
 854  *
 855  * This is supposed to be called while holding the lock. The lock is
 856  * dropped before going to sleep and is reacquired afterwards.
 857  */
 858 #define wait_event_lock_irq(wq, condition, lock)                        \
 859 do {                                                                    \
 860         if (condition)                                                  \
 861                 break;                                                  \
 862         __wait_event_lock_irq(wq, condition, lock, );                   \
 863 } while (0)
 864
 865
 866 #define __wait_event_interruptible_lock_irq(wq, condition, lock, cmd)   \
 867         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 868                       spin_unlock_irq(&lock);                           \
 869                       cmd;                                              \
 870                       schedule();                                       \
 871                       spin_lock_irq(&lock))
 872
 873 /**
 874  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
 875  *              The condition is checked under the lock. This is expected to
 876  *              be called with the lock taken.
 877  * @wq: the waitqueue to wait on
 878  * @condition: a C expression for the event to wait for
 879  * @lock: a locked spinlock_t, which will be released before cmd and
 880  *        schedule() and reacquired afterwards.
 881  * @cmd: a command which is invoked outside the critical section before
 882  *       sleep
 883  *
 884  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 885  * @condition evaluates to true or a signal is received. The @condition is
 886  * checked each time the waitqueue @wq is woken up.
 887  *
 888  * wake_up() has to be called after changing any variable that could
 889  * change the result of the wait condition.
 890  *
 891  * This is supposed to be called while holding the lock. The lock is
 892  * dropped before invoking the cmd and going to sleep and is reacquired
 893  * afterwards.
 894  *
 895  * The macro will return -ERESTARTSYS if it was interrupted by a signal
 896  * and 0 if @condition evaluated to true.
 897  */
 898 #define wait_event_interruptible_lock_irq_cmd(wq, condition, lock, cmd) \
 899 ({                                                                      \
 900         int __ret = 0;                                                  \
 901         if (!(condition))                                               \
 902                 __ret = __wait_event_interruptible_lock_irq(wq,         \
 903                                                 condition, lock, cmd);  \
 904         __ret;                                                          \
 905 })
 906
 907 /**
 908  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
 909  *              The condition is checked under the lock. This is expected
 910  *              to be called with the lock taken.
 911  * @wq: the waitqueue to wait on
 912  * @condition: a C expression for the event to wait for
 913  * @lock: a locked spinlock_t, which will be released before schedule()
 914  *        and reacquired afterwards.
 915  *
 916  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 917  * @condition evaluates to true or signal is received. The @condition is
 918  * checked each time the waitqueue @wq is woken up.
 919  *
 920  * wake_up() has to be called after changing any variable that could
 921  * change the result of the wait condition.
 922  *
 923  * This is supposed to be called while holding the lock. The lock is
 924  * dropped before going to sleep and is reacquired afterwards.
 925  *
 926  * The macro will return -ERESTARTSYS if it was interrupted by a signal
 927  * and 0 if @condition evaluated to true.
 928  */
 929 #define wait_event_interruptible_lock_irq(wq, condition, lock)          \
 930 ({                                                                      \
 931         int __ret = 0;                                                  \
 932         if (!(condition))                                               \
 933                 __ret = __wait_event_interruptible_lock_irq(wq,         \
 934                                                 condition, lock,);      \
 935         __ret;                                                          \
 936 })
 937
 938 #define __wait_event_interruptible_lock_irq_timeout(wq, condition,      \
 939                                                     lock, timeout)      \
 940         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 941                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 942                       spin_unlock_irq(&lock);                           \
 943                       __ret = schedule_timeout(__ret);                  \
 944                       spin_lock_irq(&lock));
 945
 946 /**
 947  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
 948  *              true or a timeout elapses. The condition is checked under
 949  *              the lock. This is expected to be called with the lock taken.
 950  * @wq: the waitqueue to wait on
 951  * @condition: a C expression for the event to wait for
 952  * @lock: a locked spinlock_t, which will be released before schedule()
 953  *        and reacquired afterwards.
 954  * @timeout: timeout, in jiffies
 955  *
 956  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 957  * @condition evaluates to true or signal is received. The @condition is
 958  * checked each time the waitqueue @wq is woken up.
 959  *
 960  * wake_up() has to be called after changing any variable that could
 961  * change the result of the wait condition.
 962  *
 963  * This is supposed to be called while holding the lock. The lock is
 964  * dropped before going to sleep and is reacquired afterwards.
 965  *
 966  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
 967  * was interrupted by a signal, and the remaining jiffies otherwise
 968  * if the condition evaluated to true before the timeout elapsed.
 969  */
 970 #define wait_event_interruptible_lock_irq_timeout(wq, condition, lock,  \
 971                                                   timeout)              \
 972 ({                                                                      \
 973         long __ret = timeout;                                           \
 974         if (!___wait_cond_timeout(condition))                           \
 975                 __ret = __wait_event_interruptible_lock_irq_timeout(    \
 976                                         wq, condition, lock, timeout);  \
 977         __ret;                                                          \
 978 })
 979
 980 /*
 981  * Waitqueues which are removed from the waitqueue_head at wakeup time
 982  */
 983 void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
 984 void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
 985 long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
 986 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
 987 void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key);
 988 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout);
 989 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 990 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 991 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 992
 993 #define DEFINE_WAIT_FUNC(name, function)                                \
 994         wait_queue_t name = {                                           \
 995                 .private        = current,                              \
 996                 .func           = function,                             \
 997                 .task_list      = LIST_HEAD_INIT((name).task_list),     \
 998         }
 999
1000 #define DEFINE_WAIT(name) DEFINE_WAIT_FUNC(name, autoremove_wake_function)
1001
1002 #define DEFINE_WAIT_BIT(name, word, bit)                                \
1003         struct wait_bit_queue name = {                                  \
1004                 .key = __WAIT_BIT_KEY_INITIALIZER(word, bit),           \
1005                 .wait   = {                                             \
1006                         .private        = current,                      \
1007                         .func           = wake_bit_function,            \
1008                         .task_list      =                               \
1009                                 LIST_HEAD_INIT((name).wait.task_list),  \
1010                 },                                                      \
1011         }
1012
1013 #define init_wait(wait)                                                 \
1014         do {                                                            \
1015                 (wait)->private = current;                              \
1016                 (wait)->func = autoremove_wake_function;                \
1017                 INIT_LIST_HEAD(&(wait)->task_list);                     \
1018                 (wait)->flags = 0;                                      \
1019         } while (0)
1020
1021
1022 extern int bit_wait(struct wait_bit_key *, int);
1023 extern int bit_wait_io(struct wait_bit_key *, int);
1024 extern int bit_wait_timeout(struct wait_bit_key *, int);
1025 extern int bit_wait_io_timeout(struct wait_bit_key *, int);
1026
1027 /**
1028  * wait_on_bit - wait for a bit to be cleared
1029  * @word: the word being waited on, a kernel virtual address
1030  * @bit: the bit of the word being waited on
1031  * @mode: the task state to sleep in
1032  *
1033  * There is a standard hashed waitqueue table for generic use. This
1034  * is the part of the hashtable's accessor API that waits on a bit.
1035  * For instance, if one were to have waiters on a bitflag, one would
1036  * call wait_on_bit() in threads waiting for the bit to clear.
1037  * One uses wait_on_bit() where one is waiting for the bit to clear,
1038  * but has no intention of setting it.
1039  * Returned value will be zero if the bit was cleared, or non-zero
1040  * if the process received a signal and the mode permitted wakeup
1041  * on that signal.
1042  */
1043 static inline int
1044 wait_on_bit(unsigned long *word, int bit, unsigned mode)
1045 {
1046         might_sleep();
1047         if (!test_bit(bit, word))
1048                 return 0;
1049         return out_of_line_wait_on_bit(word, bit,
1050                                        bit_wait,
1051                                        mode);
1052 }
1053
1054 /**
1055  * wait_on_bit_io - wait for a bit to be cleared
1056  * @word: the word being waited on, a kernel virtual address
1057  * @bit: the bit of the word being waited on
1058  * @mode: the task state to sleep in
1059  *
1060  * Use the standard hashed waitqueue table to wait for a bit
1061  * to be cleared.  This is similar to wait_on_bit(), but calls
1062  * io_schedule() instead of schedule() for the actual waiting.
1063  *
1064  * Returned value will be zero if the bit was cleared, or non-zero
1065  * if the process received a signal and the mode permitted wakeup
1066  * on that signal.
1067  */
1068 static inline int
1069 wait_on_bit_io(unsigned long *word, int bit, unsigned mode)
1070 {
1071         might_sleep();
1072         if (!test_bit(bit, word))
1073                 return 0;
1074         return out_of_line_wait_on_bit(word, bit,
1075                                        bit_wait_io,
1076                                        mode);
1077 }
1078
1079 /**
1080  * wait_on_bit_timeout - wait for a bit to be cleared or a timeout elapses
1081  * @word: the word being waited on, a kernel virtual address
1082  * @bit: the bit of the word being waited on
1083  * @mode: the task state to sleep in
1084  * @timeout: timeout, in jiffies
1085  *
1086  * Use the standard hashed waitqueue table to wait for a bit
1087  * to be cleared. This is similar to wait_on_bit(), except also takes a
1088  * timeout parameter.
1089  *
1090  * Returned value will be zero if the bit was cleared before the
1091  * @timeout elapsed, or non-zero if the @timeout elapsed or process
1092  * received a signal and the mode permitted wakeup on that signal.
1093  */
1094 static inline int
1095 wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode,
1096                     unsigned long timeout)
1097 {
1098         might_sleep();
1099         if (!test_bit(bit, word))
1100                 return 0;
1101         return out_of_line_wait_on_bit_timeout(word, bit,
1102                                                bit_wait_timeout,
1103                                                mode, timeout);
1104 }
1105
1106 /**
1107  * wait_on_bit_action - wait for a bit to be cleared
1108  * @word: the word being waited on, a kernel virtual address
1109  * @bit: the bit of the word being waited on
1110  * @action: the function used to sleep, which may take special actions
1111  * @mode: the task state to sleep in
1112  *
1113  * Use the standard hashed waitqueue table to wait for a bit
1114  * to be cleared, and allow the waiting action to be specified.
1115  * This is like wait_on_bit() but allows fine control of how the waiting
1116  * is done.
1117  *
1118  * Returned value will be zero if the bit was cleared, or non-zero
1119  * if the process received a signal and the mode permitted wakeup
1120  * on that signal.
1121  */
1122 static inline int
1123 wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action,
1124                    unsigned mode)
1125 {
1126         might_sleep();
1127         if (!test_bit(bit, word))
1128                 return 0;
1129         return out_of_line_wait_on_bit(word, bit, action, mode);
1130 }
1131
1132 /**
1133  * wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it
1134  * @word: the word being waited on, a kernel virtual address
1135  * @bit: the bit of the word being waited on
1136  * @mode: the task state to sleep in
1137  *
1138  * There is a standard hashed waitqueue table for generic use. This
1139  * is the part of the hashtable's accessor API that waits on a bit
1140  * when one intends to set it, for instance, trying to lock bitflags.
1141  * For instance, if one were to have waiters trying to set bitflag
1142  * and waiting for it to clear before setting it, one would call
1143  * wait_on_bit() in threads waiting to be able to set the bit.
1144  * One uses wait_on_bit_lock() where one is waiting for the bit to
1145  * clear with the intention of setting it, and when done, clearing it.
1146  *
1147  * Returns zero if the bit was (eventually) found to be clear and was
1148  * set.  Returns non-zero if a signal was delivered to the process and
1149  * the @mode allows that signal to wake the process.
1150  */
1151 static inline int
1152 wait_on_bit_lock(unsigned long *word, int bit, unsigned mode)
1153 {
1154         might_sleep();
1155         if (!test_and_set_bit(bit, word))
1156                 return 0;
1157         return out_of_line_wait_on_bit_lock(word, bit, bit_wait, mode);
1158 }
1159
1160 /**
1161  * wait_on_bit_lock_io - wait for a bit to be cleared, when wanting to set it
1162  * @word: the word being waited on, a kernel virtual address
1163  * @bit: the bit of the word being waited on
1164  * @mode: the task state to sleep in
1165  *
1166  * Use the standard hashed waitqueue table to wait for a bit
1167  * to be cleared and then to atomically set it.  This is similar
1168  * to wait_on_bit(), but calls io_schedule() instead of schedule()
1169  * for the actual waiting.
1170  *
1171  * Returns zero if the bit was (eventually) found to be clear and was
1172  * set.  Returns non-zero if a signal was delivered to the process and
1173  * the @mode allows that signal to wake the process.
1174  */
1175 static inline int
1176 wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode)
1177 {
1178         might_sleep();
1179         if (!test_and_set_bit(bit, word))
1180                 return 0;
1181         return out_of_line_wait_on_bit_lock(word, bit, bit_wait_io, mode);
1182 }
1183
1184 /**
1185  * wait_on_bit_lock_action - wait for a bit to be cleared, when wanting to set it
1186  * @word: the word being waited on, a kernel virtual address
1187  * @bit: the bit of the word being waited on
1188  * @action: the function used to sleep, which may take special actions
1189  * @mode: the task state to sleep in
1190  *
1191  * Use the standard hashed waitqueue table to wait for a bit
1192  * to be cleared and then to set it, and allow the waiting action
1193  * to be specified.
1194  * This is like wait_on_bit() but allows fine control of how the waiting
1195  * is done.
1196  *
1197  * Returns zero if the bit was (eventually) found to be clear and was
1198  * set.  Returns non-zero if a signal was delivered to the process and
1199  * the @mode allows that signal to wake the process.
1200  */
1201 static inline int
1202 wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action,
1203                         unsigned mode)
1204 {
1205         might_sleep();
1206         if (!test_and_set_bit(bit, word))
1207                 return 0;
1208         return out_of_line_wait_on_bit_lock(word, bit, action, mode);
1209 }
1210
1211 /**
1212  * wait_on_atomic_t - Wait for an atomic_t to become 0
1213  * @val: The atomic value being waited on, a kernel virtual address
1214  * @action: the function used to sleep, which may take special actions
1215  * @mode: the task state to sleep in
1216  *
1217  * Wait for an atomic_t to become 0.  We abuse the bit-wait waitqueue table for
1218  * the purpose of getting a waitqueue, but we set the key to a bit number
1219  * outside of the target 'word'.
1220  */
1221 static inline
1222 int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
1223 {
1224         might_sleep();
1225         if (atomic_read(val) == 0)
1226                 return 0;
1227         return out_of_line_wait_on_atomic_t(val, action, mode);
1228 }
1229
1230 #endif /* _LINUX_WAIT_H */