include/linux/completion.h

   1 #ifndef __LINUX_COMPLETION_H
   2 #define __LINUX_COMPLETION_H
   3
   4 /*
   5  * (C) Copyright 2001 Linus Torvalds
   6  *
   7  * Atomic wait-for-completion handler data structures.
   8  * See kernel/sched.c for details.
   9  */
  10
  11 #include <linux/wait.h>
  12
  13 struct completion {
  14         unsigned int done;
  15         wait_queue_head_t wait;
  16 };
  17
  18 #define COMPLETION_INITIALIZER(work) \
  19         { 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait) }
  20
  21 #define COMPLETION_INITIALIZER_ONSTACK(work) \
  22         ({ init_completion(&work); work; })
  23
  24 #define DECLARE_COMPLETION(work) \
  25         struct completion work = COMPLETION_INITIALIZER(work)
  26
  27 /*
  28  * Lockdep needs to run a non-constant initializer for on-stack
  29  * completions - so we use the _ONSTACK() variant for those that
  30  * are on the kernel stack:
  31  */
  32 #ifdef CONFIG_LOCKDEP
  33 # define DECLARE_COMPLETION_ONSTACK(work) \
  34         struct completion work = COMPLETION_INITIALIZER_ONSTACK(work)
  35 #else
  36 # define DECLARE_COMPLETION_ONSTACK(work) DECLARE_COMPLETION(work)
  37 #endif
  38
  39 static inline void init_completion(struct completion *x)
  40 {
  41         x->done = 0;
  42         init_waitqueue_head(&x->wait);
  43 }
  44
  45 extern void wait_for_completion(struct completion *);
  46 extern int wait_for_completion_interruptible(struct completion *x);
  47 extern int wait_for_completion_killable(struct completion *x);
  48 extern unsigned long wait_for_completion_timeout(struct completion *x,
  49                                                    unsigned long timeout);
  50 extern unsigned long wait_for_completion_interruptible_timeout(
  51                         struct completion *x, unsigned long timeout);
  52
  53 extern void complete(struct completion *);
  54 extern void complete_all(struct completion *);
  55
  56 #define INIT_COMPLETION(x)      ((x).done = 0)
  57
  58
  59 /**
  60  *      try_wait_for_completion - try to decrement a completion without blocking
  61  *      @x:     completion structure
  62  *
  63  *      Returns: 0 if a decrement cannot be done without blocking
  64  *               1 if a decrement succeeded.
  65  *
  66  *      If a completion is being used as a counting completion,
  67  *      attempt to decrement the counter without blocking. This
  68  *      enables us to avoid waiting if the resource the completion
  69  *      is protecting is not available.
  70  */
  71 static inline bool try_wait_for_completion(struct completion *x)
  72 {
  73         int ret = 1;
  74
  75         spin_lock_irq(&x->wait.lock);
  76         if (!x->done)
  77                 ret = 0;
  78         else
  79                 x->done--;
  80         spin_unlock_irq(&x->wait.lock);
  81         return ret;
  82 }
  83
  84 /**
  85  *      completion_done - Test to see if a completion has any waiters
  86  *      @x:     completion structure
  87  *
  88  *      Returns: 0 if there are waiters (wait_for_completion() in progress)
  89  *               1 if there are no waiters.
  90  *
  91  */
  92 static inline bool completion_done(struct completion *x)
  93 {
  94         int ret = 1;
  95
  96         spin_lock_irq(&x->wait.lock);
  97         if (!x->done)
  98                 ret = 0;
  99         spin_unlock_irq(&x->wait.lock);
 100         return ret;
 101 }
 102
 103 #endif