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 extern void init_wait_entry(wait_queue_t *__wait, int flags);
 252
 253 /*
 254  * The below macro ___wait_event() has an explicit shadow of the __ret
 255  * variable when used from the wait_event_*() macros.
 256  *
 257  * This is so that both can use the ___wait_cond_timeout() construct
 258  * to wrap the condition.
 259  *
 260  * The type inconsistency of the wait_event_*() __ret variable is also
 261  * on purpose; we use long where we can return timeout values and int
 262  * otherwise.
 263  */
 264
 265 #define ___wait_event(wq, condition, state, exclusive, ret, cmd)        \
 266 ({                                                                      \
 267         __label__ __out;                                                \
 268         wait_queue_t __wait;                                            \
 269         long __ret = ret;       /* explicit shadow */                   \
 270                                                                         \
 271         init_wait_entry(&__wait, exclusive ? WQ_FLAG_EXCLUSIVE : 0);    \
 272         for (;;) {                                                      \
 273                 long __int = prepare_to_wait_event(&wq, &__wait, state);\
 274                                                                         \
 275                 if (condition)                                          \
 276                         break;                                          \
 277                                                                         \
 278                 if (___wait_is_interruptible(state) && __int) {         \
 279                         __ret = __int;                                  \
 280                         goto __out;                                     \
 281                 }                                                       \
 282                                                                         \
 283                 cmd;                                                    \
 284         }                                                               \
 285         finish_wait(&wq, &__wait);                                      \
 286 __out:  __ret;                                                          \
 287 })
 288
 289 #define __wait_event(wq, condition)                                     \
 290         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 291                             schedule())
 292
 293 /**
 294  * wait_event - sleep until a condition gets true
 295  * @wq: the waitqueue to wait on
 296  * @condition: a C expression for the event to wait for
 297  *
 298  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 299  * @condition evaluates to true. The @condition is checked each time
 300  * the waitqueue @wq is woken up.
 301  *
 302  * wake_up() has to be called after changing any variable that could
 303  * change the result of the wait condition.
 304  */
 305 #define wait_event(wq, condition)                                       \
 306 do {                                                                    \
 307         might_sleep();                                                  \
 308         if (condition)                                                  \
 309                 break;                                                  \
 310         __wait_event(wq, condition);                                    \
 311 } while (0)
 312
 313 #define __io_wait_event(wq, condition)                                  \
 314         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 315                             io_schedule())
 316
 317 /*
 318  * io_wait_event() -- like wait_event() but with io_schedule()
 319  */
 320 #define io_wait_event(wq, condition)                                    \
 321 do {                                                                    \
 322         might_sleep();                                                  \
 323         if (condition)                                                  \
 324                 break;                                                  \
 325         __io_wait_event(wq, condition);                                 \
 326 } while (0)
 327
 328 #define __wait_event_freezable(wq, condition)                           \
 329         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 330                             schedule(); try_to_freeze())
 331
 332 /**
 333  * wait_event_freezable - sleep (or freeze) until a condition gets true
 334  * @wq: the waitqueue to wait on
 335  * @condition: a C expression for the event to wait for
 336  *
 337  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
 338  * to system load) until the @condition evaluates to true. The
 339  * @condition is checked each time the waitqueue @wq is woken up.
 340  *
 341  * wake_up() has to be called after changing any variable that could
 342  * change the result of the wait condition.
 343  */
 344 #define wait_event_freezable(wq, condition)                             \
 345 ({                                                                      \
 346         int __ret = 0;                                                  \
 347         might_sleep();                                                  \
 348         if (!(condition))                                               \
 349                 __ret = __wait_event_freezable(wq, condition);          \
 350         __ret;                                                          \
 351 })
 352
 353 #define __wait_event_timeout(wq, condition, timeout)                    \
 354         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 355                       TASK_UNINTERRUPTIBLE, 0, timeout,                 \
 356                       __ret = schedule_timeout(__ret))
 357
 358 /**
 359  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
 360  * @wq: the waitqueue to wait on
 361  * @condition: a C expression for the event to wait for
 362  * @timeout: timeout, in jiffies
 363  *
 364  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 365  * @condition evaluates to true. The @condition is checked each time
 366  * the waitqueue @wq is woken up.
 367  *
 368  * wake_up() has to be called after changing any variable that could
 369  * change the result of the wait condition.
 370  *
 371  * Returns:
 372  * 0 if the @condition evaluated to %false after the @timeout elapsed,
 373  * 1 if the @condition evaluated to %true after the @timeout elapsed,
 374  * or the remaining jiffies (at least 1) if the @condition evaluated
 375  * to %true before the @timeout elapsed.
 376  */
 377 #define wait_event_timeout(wq, condition, timeout)                      \
 378 ({                                                                      \
 379         long __ret = timeout;                                           \
 380         might_sleep();                                                  \
 381         if (!___wait_cond_timeout(condition))                           \
 382                 __ret = __wait_event_timeout(wq, condition, timeout);   \
 383         __ret;                                                          \
 384 })
 385
 386 #define __wait_event_freezable_timeout(wq, condition, timeout)          \
 387         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 388                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 389                       __ret = schedule_timeout(__ret); try_to_freeze())
 390
 391 /*
 392  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
 393  * increasing load and is freezable.
 394  */
 395 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 396 ({                                                                      \
 397         long __ret = timeout;                                           \
 398         might_sleep();                                                  \
 399         if (!___wait_cond_timeout(condition))                           \
 400                 __ret = __wait_event_freezable_timeout(wq, condition, timeout); \
 401         __ret;                                                          \
 402 })
 403
 404 #define __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2)           \
 405         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 1, 0,  \
 406                             cmd1; schedule(); cmd2)
 407 /*
 408  * Just like wait_event_cmd(), except it sets exclusive flag
 409  */
 410 #define wait_event_exclusive_cmd(wq, condition, cmd1, cmd2)             \
 411 do {                                                                    \
 412         if (condition)                                                  \
 413                 break;                                                  \
 414         __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2);          \
 415 } while (0)
 416
 417 #define __wait_event_cmd(wq, condition, cmd1, cmd2)                     \
 418         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 419                             cmd1; schedule(); cmd2)
 420
 421 /**
 422  * wait_event_cmd - sleep until a condition gets true
 423  * @wq: the waitqueue to wait on
 424  * @condition: a C expression for the event to wait for
 425  * @cmd1: the command will be executed before sleep
 426  * @cmd2: the command will be executed after sleep
 427  *
 428  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 429  * @condition evaluates to true. The @condition is checked each time
 430  * the waitqueue @wq is woken up.
 431  *
 432  * wake_up() has to be called after changing any variable that could
 433  * change the result of the wait condition.
 434  */
 435 #define wait_event_cmd(wq, condition, cmd1, cmd2)                       \
 436 do {                                                                    \
 437         if (condition)                                                  \
 438                 break;                                                  \
 439         __wait_event_cmd(wq, condition, cmd1, cmd2);                    \
 440 } while (0)
 441
 442 #define __wait_event_interruptible(wq, condition)                       \
 443         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 444                       schedule())
 445
 446 /**
 447  * wait_event_interruptible - sleep until a condition gets true
 448  * @wq: the waitqueue to wait on
 449  * @condition: a C expression for the event to wait for
 450  *
 451  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 452  * @condition evaluates to true or a signal is received.
 453  * The @condition is checked each time the waitqueue @wq is woken up.
 454  *
 455  * wake_up() has to be called after changing any variable that could
 456  * change the result of the wait condition.
 457  *
 458  * The function will return -ERESTARTSYS if it was interrupted by a
 459  * signal and 0 if @condition evaluated to true.
 460  */
 461 #define wait_event_interruptible(wq, condition)                         \
 462 ({                                                                      \
 463         int __ret = 0;                                                  \
 464         might_sleep();                                                  \
 465         if (!(condition))                                               \
 466                 __ret = __wait_event_interruptible(wq, condition);      \
 467         __ret;                                                          \
 468 })
 469
 470 #define __wait_event_interruptible_timeout(wq, condition, timeout)      \
 471         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 472                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 473                       __ret = schedule_timeout(__ret))
 474
 475 /**
 476  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
 477  * @wq: the waitqueue to wait on
 478  * @condition: a C expression for the event to wait for
 479  * @timeout: timeout, in jiffies
 480  *
 481  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 482  * @condition evaluates to true or a signal is received.
 483  * The @condition is checked each time the waitqueue @wq is woken up.
 484  *
 485  * wake_up() has to be called after changing any variable that could
 486  * change the result of the wait condition.
 487  *
 488  * Returns:
 489  * 0 if the @condition evaluated to %false after the @timeout elapsed,
 490  * 1 if the @condition evaluated to %true after the @timeout elapsed,
 491  * the remaining jiffies (at least 1) if the @condition evaluated
 492  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
 493  * interrupted by a signal.
 494  */
 495 #define wait_event_interruptible_timeout(wq, condition, timeout)        \
 496 ({                                                                      \
 497         long __ret = timeout;                                           \
 498         might_sleep();                                                  \
 499         if (!___wait_cond_timeout(condition))                           \
 500                 __ret = __wait_event_interruptible_timeout(wq,          \
 501                                                 condition, timeout);    \
 502         __ret;                                                          \
 503 })
 504
 505 #define __wait_event_hrtimeout(wq, condition, timeout, state)           \
 506 ({                                                                      \
 507         int __ret = 0;                                                  \
 508         struct hrtimer_sleeper __t;                                     \
 509                                                                         \
 510         hrtimer_init_on_stack(&__t.timer, CLOCK_MONOTONIC,              \
 511                               HRTIMER_MODE_REL);                        \
 512         hrtimer_init_sleeper(&__t, current);                            \
 513         if ((timeout).tv64 != KTIME_MAX)                                \
 514                 hrtimer_start_range_ns(&__t.timer, timeout,             \
 515                                        current->timer_slack_ns,         \
 516                                        HRTIMER_MODE_REL);               \
 517                                                                         \
 518         __ret = ___wait_event(wq, condition, state, 0, 0,               \
 519                 if (!__t.task) {                                        \
 520                         __ret = -ETIME;                                 \
 521                         break;                                          \
 522                 }                                                       \
 523                 schedule());                                            \
 524                                                                         \
 525         hrtimer_cancel(&__t.timer);                                     \
 526         destroy_hrtimer_on_stack(&__t.timer);                           \
 527         __ret;                                                          \
 528 })
 529
 530 /**
 531  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
 532  * @wq: the waitqueue to wait on
 533  * @condition: a C expression for the event to wait for
 534  * @timeout: timeout, as a ktime_t
 535  *
 536  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 537  * @condition evaluates to true or a signal is received.
 538  * The @condition is checked each time the waitqueue @wq is woken up.
 539  *
 540  * wake_up() has to be called after changing any variable that could
 541  * change the result of the wait condition.
 542  *
 543  * The function returns 0 if @condition became true, or -ETIME if the timeout
 544  * elapsed.
 545  */
 546 #define wait_event_hrtimeout(wq, condition, timeout)                    \
 547 ({                                                                      \
 548         int __ret = 0;                                                  \
 549         might_sleep();                                                  \
 550         if (!(condition))                                               \
 551                 __ret = __wait_event_hrtimeout(wq, condition, timeout,  \
 552                                                TASK_UNINTERRUPTIBLE);   \
 553         __ret;                                                          \
 554 })
 555
 556 /**
 557  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
 558  * @wq: the waitqueue to wait on
 559  * @condition: a C expression for the event to wait for
 560  * @timeout: timeout, as a ktime_t
 561  *
 562  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 563  * @condition evaluates to true or a signal is received.
 564  * The @condition is checked each time the waitqueue @wq is woken up.
 565  *
 566  * wake_up() has to be called after changing any variable that could
 567  * change the result of the wait condition.
 568  *
 569  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
 570  * interrupted by a signal, or -ETIME if the timeout elapsed.
 571  */
 572 #define wait_event_interruptible_hrtimeout(wq, condition, timeout)      \
 573 ({                                                                      \
 574         long __ret = 0;                                                 \
 575         might_sleep();                                                  \
 576         if (!(condition))                                               \
 577                 __ret = __wait_event_hrtimeout(wq, condition, timeout,  \
 578                                                TASK_INTERRUPTIBLE);     \
 579         __ret;                                                          \
 580 })
 581
 582 #define __wait_event_interruptible_exclusive(wq, condition)             \
 583         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,          \
 584                       schedule())
 585
 586 #define wait_event_interruptible_exclusive(wq, condition)               \
 587 ({                                                                      \
 588         int __ret = 0;                                                  \
 589         might_sleep();                                                  \
 590         if (!(condition))                                               \
 591                 __ret = __wait_event_interruptible_exclusive(wq, condition);\
 592         __ret;                                                          \
 593 })
 594
 595 #define __wait_event_killable_exclusive(wq, condition)                  \
 596         ___wait_event(wq, condition, TASK_KILLABLE, 1, 0,               \
 597                       schedule())
 598
 599 #define wait_event_killable_exclusive(wq, condition)                    \
 600 ({                                                                      \
 601         int __ret = 0;                                                  \
 602         might_sleep();                                                  \
 603         if (!(condition))                                               \
 604                 __ret = __wait_event_killable_exclusive(wq, condition); \
 605         __ret;                                                          \
 606 })
 607
 608
 609 #define __wait_event_freezable_exclusive(wq, condition)                 \
 610         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,          \
 611                         schedule(); try_to_freeze())
 612
 613 #define wait_event_freezable_exclusive(wq, condition)                   \
 614 ({                                                                      \
 615         int __ret = 0;                                                  \
 616         might_sleep();                                                  \
 617         if (!(condition))                                               \
 618                 __ret = __wait_event_freezable_exclusive(wq, condition);\
 619         __ret;                                                          \
 620 })
 621
 622
 623 #define __wait_event_interruptible_locked(wq, condition, exclusive, irq) \
 624 ({                                                                      \
 625         int __ret = 0;                                                  \
 626         DEFINE_WAIT(__wait);                                            \
 627         if (exclusive)                                                  \
 628                 __wait.flags |= WQ_FLAG_EXCLUSIVE;                      \
 629         do {                                                            \
 630                 if (likely(list_empty(&__wait.task_list)))              \
 631                         __add_wait_queue_tail(&(wq), &__wait);          \
 632                 set_current_state(TASK_INTERRUPTIBLE);                  \
 633                 if (signal_pending(current)) {                          \
 634                         __ret = -ERESTARTSYS;                           \
 635                         break;                                          \
 636                 }                                                       \
 637                 if (irq)                                                \
 638                         spin_unlock_irq(&(wq).lock);                    \
 639                 else                                                    \
 640                         spin_unlock(&(wq).lock);                        \
 641                 schedule();                                             \
 642                 if (irq)                                                \
 643                         spin_lock_irq(&(wq).lock);                      \
 644                 else                                                    \
 645                         spin_lock(&(wq).lock);                          \
 646         } while (!(condition));                                         \
 647         __remove_wait_queue(&(wq), &__wait);                            \
 648         __set_current_state(TASK_RUNNING);                              \
 649         __ret;                                                          \
 650 })
 651
 652
 653 /**
 654  * wait_event_interruptible_locked - sleep until a condition gets true
 655  * @wq: the waitqueue to wait on
 656  * @condition: a C expression for the event to wait for
 657  *
 658  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 659  * @condition evaluates to true or a signal is received.
 660  * The @condition is checked each time the waitqueue @wq is woken up.
 661  *
 662  * It must be called with wq.lock being held.  This spinlock is
 663  * unlocked while sleeping but @condition testing is done while lock
 664  * is held and when this macro exits the lock is held.
 665  *
 666  * The lock is locked/unlocked using spin_lock()/spin_unlock()
 667  * functions which must match the way they are locked/unlocked outside
 668  * of this macro.
 669  *
 670  * wake_up_locked() has to be called after changing any variable that could
 671  * change the result of the wait condition.
 672  *
 673  * The function will return -ERESTARTSYS if it was interrupted by a
 674  * signal and 0 if @condition evaluated to true.
 675  */
 676 #define wait_event_interruptible_locked(wq, condition)                  \
 677         ((condition)                                                    \
 678          ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 0))
 679
 680 /**
 681  * wait_event_interruptible_locked_irq - sleep until a condition gets true
 682  * @wq: the waitqueue to wait on
 683  * @condition: a C expression for the event to wait for
 684  *
 685  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 686  * @condition evaluates to true or a signal is received.
 687  * The @condition is checked each time the waitqueue @wq is woken up.
 688  *
 689  * It must be called with wq.lock being held.  This spinlock is
 690  * unlocked while sleeping but @condition testing is done while lock
 691  * is held and when this macro exits the lock is held.
 692  *
 693  * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()
 694  * functions which must match the way they are locked/unlocked outside
 695  * of this macro.
 696  *
 697  * wake_up_locked() has to be called after changing any variable that could
 698  * change the result of the wait condition.
 699  *
 700  * The function will return -ERESTARTSYS if it was interrupted by a
 701  * signal and 0 if @condition evaluated to true.
 702  */
 703 #define wait_event_interruptible_locked_irq(wq, condition)              \
 704         ((condition)                                                    \
 705          ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 1))
 706
 707 /**
 708  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
 709  * @wq: the waitqueue to wait on
 710  * @condition: a C expression for the event to wait for
 711  *
 712  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 713  * @condition evaluates to true or a signal is received.
 714  * The @condition is checked each time the waitqueue @wq is woken up.
 715  *
 716  * It must be called with wq.lock being held.  This spinlock is
 717  * unlocked while sleeping but @condition testing is done while lock
 718  * is held and when this macro exits the lock is held.
 719  *
 720  * The lock is locked/unlocked using spin_lock()/spin_unlock()
 721  * functions which must match the way they are locked/unlocked outside
 722  * of this macro.
 723  *
 724  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
 725  * set thus when other process waits process on the list if this
 726  * process is awaken further processes are not considered.
 727  *
 728  * wake_up_locked() has to be called after changing any variable that could
 729  * change the result of the wait condition.
 730  *
 731  * The function will return -ERESTARTSYS if it was interrupted by a
 732  * signal and 0 if @condition evaluated to true.
 733  */
 734 #define wait_event_interruptible_exclusive_locked(wq, condition)        \
 735         ((condition)                                                    \
 736          ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 0))
 737
 738 /**
 739  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
 740  * @wq: the waitqueue to wait on
 741  * @condition: a C expression for the event to wait for
 742  *
 743  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 744  * @condition evaluates to true or a signal is received.
 745  * The @condition is checked each time the waitqueue @wq is woken up.
 746  *
 747  * It must be called with wq.lock being held.  This spinlock is
 748  * unlocked while sleeping but @condition testing is done while lock
 749  * is held and when this macro exits the lock is held.
 750  *
 751  * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()
 752  * functions which must match the way they are locked/unlocked outside
 753  * of this macro.
 754  *
 755  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
 756  * set thus when other process waits process on the list if this
 757  * process is awaken further processes are not considered.
 758  *
 759  * wake_up_locked() has to be called after changing any variable that could
 760  * change the result of the wait condition.
 761  *
 762  * The function will return -ERESTARTSYS if it was interrupted by a
 763  * signal and 0 if @condition evaluated to true.
 764  */
 765 #define wait_event_interruptible_exclusive_locked_irq(wq, condition)    \
 766         ((condition)                                                    \
 767          ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 1))
 768
 769
 770 #define __wait_event_killable(wq, condition)                            \
 771         ___wait_event(wq, condition, TASK_KILLABLE, 0, 0, schedule())
 772
 773 /**
 774  * wait_event_killable - sleep until a condition gets true
 775  * @wq: the waitqueue to wait on
 776  * @condition: a C expression for the event to wait for
 777  *
 778  * The process is put to sleep (TASK_KILLABLE) until the
 779  * @condition evaluates to true or a signal is received.
 780  * The @condition is checked each time the waitqueue @wq is woken up.
 781  *
 782  * wake_up() has to be called after changing any variable that could
 783  * change the result of the wait condition.
 784  *
 785  * The function will return -ERESTARTSYS if it was interrupted by a
 786  * signal and 0 if @condition evaluated to true.
 787  */
 788 #define wait_event_killable(wq, condition)                              \
 789 ({                                                                      \
 790         int __ret = 0;                                                  \
 791         might_sleep();                                                  \
 792         if (!(condition))                                               \
 793                 __ret = __wait_event_killable(wq, condition);           \
 794         __ret;                                                          \
 795 })
 796
 797
 798 #define __wait_event_lock_irq(wq, condition, lock, cmd)                 \
 799         (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
 800                             spin_unlock_irq(&lock);                     \
 801                             cmd;                                        \
 802                             schedule();                                 \
 803                             spin_lock_irq(&lock))
 804
 805 /**
 806  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
 807  *                           condition is checked under the lock. This
 808  *                           is expected to be called with the lock
 809  *                           taken.
 810  * @wq: the waitqueue to wait on
 811  * @condition: a C expression for the event to wait for
 812  * @lock: a locked spinlock_t, which will be released before cmd
 813  *        and schedule() and reacquired afterwards.
 814  * @cmd: a command which is invoked outside the critical section before
 815  *       sleep
 816  *
 817  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 818  * @condition evaluates to true. The @condition is checked each time
 819  * the waitqueue @wq is woken up.
 820  *
 821  * wake_up() has to be called after changing any variable that could
 822  * change the result of the wait condition.
 823  *
 824  * This is supposed to be called while holding the lock. The lock is
 825  * dropped before invoking the cmd and going to sleep and is reacquired
 826  * afterwards.
 827  */
 828 #define wait_event_lock_irq_cmd(wq, condition, lock, cmd)               \
 829 do {                                                                    \
 830         if (condition)                                                  \
 831                 break;                                                  \
 832         __wait_event_lock_irq(wq, condition, lock, cmd);                \
 833 } while (0)
 834
 835 /**
 836  * wait_event_lock_irq - sleep until a condition gets true. The
 837  *                       condition is checked under the lock. This
 838  *                       is expected to be called with the lock
 839  *                       taken.
 840  * @wq: the waitqueue to wait on
 841  * @condition: a C expression for the event to wait for
 842  * @lock: a locked spinlock_t, which will be released before schedule()
 843  *        and reacquired afterwards.
 844  *
 845  * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
 846  * @condition evaluates to true. The @condition is checked each time
 847  * the waitqueue @wq is woken up.
 848  *
 849  * wake_up() has to be called after changing any variable that could
 850  * change the result of the wait condition.
 851  *
 852  * This is supposed to be called while holding the lock. The lock is
 853  * dropped before going to sleep and is reacquired afterwards.
 854  */
 855 #define wait_event_lock_irq(wq, condition, lock)                        \
 856 do {                                                                    \
 857         if (condition)                                                  \
 858                 break;                                                  \
 859         __wait_event_lock_irq(wq, condition, lock, );                   \
 860 } while (0)
 861
 862
 863 #define __wait_event_interruptible_lock_irq(wq, condition, lock, cmd)   \
 864         ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
 865                       spin_unlock_irq(&lock);                           \
 866                       cmd;                                              \
 867                       schedule();                                       \
 868                       spin_lock_irq(&lock))
 869
 870 /**
 871  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
 872  *              The condition is checked under the lock. This is expected to
 873  *              be called with the lock taken.
 874  * @wq: the waitqueue to wait on
 875  * @condition: a C expression for the event to wait for
 876  * @lock: a locked spinlock_t, which will be released before cmd and
 877  *        schedule() and reacquired afterwards.
 878  * @cmd: a command which is invoked outside the critical section before
 879  *       sleep
 880  *
 881  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 882  * @condition evaluates to true or a signal is received. The @condition is
 883  * checked each time the waitqueue @wq is woken up.
 884  *
 885  * wake_up() has to be called after changing any variable that could
 886  * change the result of the wait condition.
 887  *
 888  * This is supposed to be called while holding the lock. The lock is
 889  * dropped before invoking the cmd and going to sleep and is reacquired
 890  * afterwards.
 891  *
 892  * The macro will return -ERESTARTSYS if it was interrupted by a signal
 893  * and 0 if @condition evaluated to true.
 894  */
 895 #define wait_event_interruptible_lock_irq_cmd(wq, condition, lock, cmd) \
 896 ({                                                                      \
 897         int __ret = 0;                                                  \
 898         if (!(condition))                                               \
 899                 __ret = __wait_event_interruptible_lock_irq(wq,         \
 900                                                 condition, lock, cmd);  \
 901         __ret;                                                          \
 902 })
 903
 904 /**
 905  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
 906  *              The condition is checked under the lock. This is expected
 907  *              to be called with the lock taken.
 908  * @wq: the waitqueue to wait on
 909  * @condition: a C expression for the event to wait for
 910  * @lock: a locked spinlock_t, which will be released before schedule()
 911  *        and reacquired afterwards.
 912  *
 913  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 914  * @condition evaluates to true or signal is received. The @condition is
 915  * checked each time the waitqueue @wq is woken up.
 916  *
 917  * wake_up() has to be called after changing any variable that could
 918  * change the result of the wait condition.
 919  *
 920  * This is supposed to be called while holding the lock. The lock is
 921  * dropped before going to sleep and is reacquired afterwards.
 922  *
 923  * The macro will return -ERESTARTSYS if it was interrupted by a signal
 924  * and 0 if @condition evaluated to true.
 925  */
 926 #define wait_event_interruptible_lock_irq(wq, condition, lock)          \
 927 ({                                                                      \
 928         int __ret = 0;                                                  \
 929         if (!(condition))                                               \
 930                 __ret = __wait_event_interruptible_lock_irq(wq,         \
 931                                                 condition, lock,);      \
 932         __ret;                                                          \
 933 })
 934
 935 #define __wait_event_interruptible_lock_irq_timeout(wq, condition,      \
 936                                                     lock, timeout)      \
 937         ___wait_event(wq, ___wait_cond_timeout(condition),              \
 938                       TASK_INTERRUPTIBLE, 0, timeout,                   \
 939                       spin_unlock_irq(&lock);                           \
 940                       __ret = schedule_timeout(__ret);                  \
 941                       spin_lock_irq(&lock));
 942
 943 /**
 944  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
 945  *              true or a timeout elapses. The condition is checked under
 946  *              the lock. This is expected to be called with the lock taken.
 947  * @wq: the waitqueue to wait on
 948  * @condition: a C expression for the event to wait for
 949  * @lock: a locked spinlock_t, which will be released before schedule()
 950  *        and reacquired afterwards.
 951  * @timeout: timeout, in jiffies
 952  *
 953  * The process is put to sleep (TASK_INTERRUPTIBLE) until the
 954  * @condition evaluates to true or signal is received. The @condition is
 955  * checked each time the waitqueue @wq is woken up.
 956  *
 957  * wake_up() has to be called after changing any variable that could
 958  * change the result of the wait condition.
 959  *
 960  * This is supposed to be called while holding the lock. The lock is
 961  * dropped before going to sleep and is reacquired afterwards.
 962  *
 963  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
 964  * was interrupted by a signal, and the remaining jiffies otherwise
 965  * if the condition evaluated to true before the timeout elapsed.
 966  */
 967 #define wait_event_interruptible_lock_irq_timeout(wq, condition, lock,  \
 968                                                   timeout)              \
 969 ({                                                                      \
 970         long __ret = timeout;                                           \
 971         if (!___wait_cond_timeout(condition))                           \
 972                 __ret = __wait_event_interruptible_lock_irq_timeout(    \
 973                                         wq, condition, lock, timeout);  \
 974         __ret;                                                          \
 975 })
 976
 977 /*
 978  * Waitqueues which are removed from the waitqueue_head at wakeup time
 979  */
 980 void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
 981 void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
 982 long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
 983 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
 984 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout);
 985 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 986 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 987 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
 988
 989 #define DEFINE_WAIT_FUNC(name, function)                                \
 990         wait_queue_t name = {                                           \
 991                 .private        = current,                              \
 992                 .func           = function,                             \
 993                 .task_list      = LIST_HEAD_INIT((name).task_list),     \
 994         }
 995
 996 #define DEFINE_WAIT(name) DEFINE_WAIT_FUNC(name, autoremove_wake_function)
 997
 998 #define DEFINE_WAIT_BIT(name, word, bit)                                \
 999         struct wait_bit_queue name = {                                  \
1000                 .key = __WAIT_BIT_KEY_INITIALIZER(word, bit),           \
1001                 .wait   = {                                             \
1002                         .private        = current,                      \
1003                         .func           = wake_bit_function,            \
1004                         .task_list      =                               \
1005                                 LIST_HEAD_INIT((name).wait.task_list),  \
1006                 },                                                      \
1007         }
1008
1009 #define init_wait(wait)                                                 \
1010         do {                                                            \
1011                 (wait)->private = current;                              \
1012                 (wait)->func = autoremove_wake_function;                \
1013                 INIT_LIST_HEAD(&(wait)->task_list);                     \
1014                 (wait)->flags = 0;                                      \
1015         } while (0)
1016
1017
1018 extern int bit_wait(struct wait_bit_key *, int);
1019 extern int bit_wait_io(struct wait_bit_key *, int);
1020 extern int bit_wait_timeout(struct wait_bit_key *, int);
1021 extern int bit_wait_io_timeout(struct wait_bit_key *, int);
1022
1023 /**
1024  * wait_on_bit - wait for a bit to be cleared
1025  * @word: the word being waited on, a kernel virtual address
1026  * @bit: the bit of the word being waited on
1027  * @mode: the task state to sleep in
1028  *
1029  * There is a standard hashed waitqueue table for generic use. This
1030  * is the part of the hashtable's accessor API that waits on a bit.
1031  * For instance, if one were to have waiters on a bitflag, one would
1032  * call wait_on_bit() in threads waiting for the bit to clear.
1033  * One uses wait_on_bit() where one is waiting for the bit to clear,
1034  * but has no intention of setting it.
1035  * Returned value will be zero if the bit was cleared, or non-zero
1036  * if the process received a signal and the mode permitted wakeup
1037  * on that signal.
1038  */
1039 static inline int
1040 wait_on_bit(unsigned long *word, int bit, unsigned mode)
1041 {
1042         might_sleep();
1043         if (!test_bit(bit, word))
1044                 return 0;
1045         return out_of_line_wait_on_bit(word, bit,
1046                                        bit_wait,
1047                                        mode);
1048 }
1049
1050 /**
1051  * wait_on_bit_io - wait for a bit to be cleared
1052  * @word: the word being waited on, a kernel virtual address
1053  * @bit: the bit of the word being waited on
1054  * @mode: the task state to sleep in
1055  *
1056  * Use the standard hashed waitqueue table to wait for a bit
1057  * to be cleared.  This is similar to wait_on_bit(), but calls
1058  * io_schedule() instead of schedule() for the actual waiting.
1059  *
1060  * Returned value will be zero if the bit was cleared, or non-zero
1061  * if the process received a signal and the mode permitted wakeup
1062  * on that signal.
1063  */
1064 static inline int
1065 wait_on_bit_io(unsigned long *word, int bit, unsigned mode)
1066 {
1067         might_sleep();
1068         if (!test_bit(bit, word))
1069                 return 0;
1070         return out_of_line_wait_on_bit(word, bit,
1071                                        bit_wait_io,
1072                                        mode);
1073 }
1074
1075 /**
1076  * wait_on_bit_timeout - wait for a bit to be cleared or a timeout elapses
1077  * @word: the word being waited on, a kernel virtual address
1078  * @bit: the bit of the word being waited on
1079  * @mode: the task state to sleep in
1080  * @timeout: timeout, in jiffies
1081  *
1082  * Use the standard hashed waitqueue table to wait for a bit
1083  * to be cleared. This is similar to wait_on_bit(), except also takes a
1084  * timeout parameter.
1085  *
1086  * Returned value will be zero if the bit was cleared before the
1087  * @timeout elapsed, or non-zero if the @timeout elapsed or process
1088  * received a signal and the mode permitted wakeup on that signal.
1089  */
1090 static inline int
1091 wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode,
1092                     unsigned long timeout)
1093 {
1094         might_sleep();
1095         if (!test_bit(bit, word))
1096                 return 0;
1097         return out_of_line_wait_on_bit_timeout(word, bit,
1098                                                bit_wait_timeout,
1099                                                mode, timeout);
1100 }
1101
1102 /**
1103  * wait_on_bit_action - wait for a bit to be cleared
1104  * @word: the word being waited on, a kernel virtual address
1105  * @bit: the bit of the word being waited on
1106  * @action: the function used to sleep, which may take special actions
1107  * @mode: the task state to sleep in
1108  *
1109  * Use the standard hashed waitqueue table to wait for a bit
1110  * to be cleared, and allow the waiting action to be specified.
1111  * This is like wait_on_bit() but allows fine control of how the waiting
1112  * is done.
1113  *
1114  * Returned value will be zero if the bit was cleared, or non-zero
1115  * if the process received a signal and the mode permitted wakeup
1116  * on that signal.
1117  */
1118 static inline int
1119 wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action,
1120                    unsigned mode)
1121 {
1122         might_sleep();
1123         if (!test_bit(bit, word))
1124                 return 0;
1125         return out_of_line_wait_on_bit(word, bit, action, mode);
1126 }
1127
1128 /**
1129  * wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it
1130  * @word: the word being waited on, a kernel virtual address
1131  * @bit: the bit of the word being waited on
1132  * @mode: the task state to sleep in
1133  *
1134  * There is a standard hashed waitqueue table for generic use. This
1135  * is the part of the hashtable's accessor API that waits on a bit
1136  * when one intends to set it, for instance, trying to lock bitflags.
1137  * For instance, if one were to have waiters trying to set bitflag
1138  * and waiting for it to clear before setting it, one would call
1139  * wait_on_bit() in threads waiting to be able to set the bit.
1140  * One uses wait_on_bit_lock() where one is waiting for the bit to
1141  * clear with the intention of setting it, and when done, clearing it.
1142  *
1143  * Returns zero if the bit was (eventually) found to be clear and was
1144  * set.  Returns non-zero if a signal was delivered to the process and
1145  * the @mode allows that signal to wake the process.
1146  */
1147 static inline int
1148 wait_on_bit_lock(unsigned long *word, int bit, unsigned mode)
1149 {
1150         might_sleep();
1151         if (!test_and_set_bit(bit, word))
1152                 return 0;
1153         return out_of_line_wait_on_bit_lock(word, bit, bit_wait, mode);
1154 }
1155
1156 /**
1157  * wait_on_bit_lock_io - wait for a bit to be cleared, when wanting to set it
1158  * @word: the word being waited on, a kernel virtual address
1159  * @bit: the bit of the word being waited on
1160  * @mode: the task state to sleep in
1161  *
1162  * Use the standard hashed waitqueue table to wait for a bit
1163  * to be cleared and then to atomically set it.  This is similar
1164  * to wait_on_bit(), but calls io_schedule() instead of schedule()
1165  * for the actual waiting.
1166  *
1167  * Returns zero if the bit was (eventually) found to be clear and was
1168  * set.  Returns non-zero if a signal was delivered to the process and
1169  * the @mode allows that signal to wake the process.
1170  */
1171 static inline int
1172 wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode)
1173 {
1174         might_sleep();
1175         if (!test_and_set_bit(bit, word))
1176                 return 0;
1177         return out_of_line_wait_on_bit_lock(word, bit, bit_wait_io, mode);
1178 }
1179
1180 /**
1181  * wait_on_bit_lock_action - wait for a bit to be cleared, when wanting to set it
1182  * @word: the word being waited on, a kernel virtual address
1183  * @bit: the bit of the word being waited on
1184  * @action: the function used to sleep, which may take special actions
1185  * @mode: the task state to sleep in
1186  *
1187  * Use the standard hashed waitqueue table to wait for a bit
1188  * to be cleared and then to set it, and allow the waiting action
1189  * to be specified.
1190  * This is like wait_on_bit() but allows fine control of how the waiting
1191  * is done.
1192  *
1193  * Returns zero if the bit was (eventually) found to be clear and was
1194  * set.  Returns non-zero if a signal was delivered to the process and
1195  * the @mode allows that signal to wake the process.
1196  */
1197 static inline int
1198 wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action,
1199                         unsigned mode)
1200 {
1201         might_sleep();
1202         if (!test_and_set_bit(bit, word))
1203                 return 0;
1204         return out_of_line_wait_on_bit_lock(word, bit, action, mode);
1205 }
1206
1207 /**
1208  * wait_on_atomic_t - Wait for an atomic_t to become 0
1209  * @val: The atomic value being waited on, a kernel virtual address
1210  * @action: the function used to sleep, which may take special actions
1211  * @mode: the task state to sleep in
1212  *
1213  * Wait for an atomic_t to become 0.  We abuse the bit-wait waitqueue table for
1214  * the purpose of getting a waitqueue, but we set the key to a bit number
1215  * outside of the target 'word'.
1216  */
1217 static inline
1218 int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
1219 {
1220         might_sleep();
1221         if (atomic_read(val) == 0)
1222                 return 0;
1223         return out_of_line_wait_on_atomic_t(val, action, mode);
1224 }
1225
1226 #endif /* _LINUX_WAIT_H */