include/linux/swait.h

   1 #ifndef _LINUX_SWAIT_H
   2 #define _LINUX_SWAIT_H
   3
   4 #include <linux/list.h>
   5 #include <linux/stddef.h>
   6 #include <linux/spinlock.h>
   7 #include <asm/current.h>
   8
   9 /*
  10  * Simple wait queues
  11  *
  12  * While these are very similar to the other/complex wait queues (wait.h) the
  13  * most important difference is that the simple waitqueue allows for
  14  * deterministic behaviour -- IOW it has strictly bounded IRQ and lock hold
  15  * times.
  16  *
  17  * In order to make this so, we had to drop a fair number of features of the
  18  * other waitqueue code; notably:
  19  *
  20  *  - mixing INTERRUPTIBLE and UNINTERRUPTIBLE sleeps on the same waitqueue;
  21  *    all wakeups are TASK_NORMAL in order to avoid O(n) lookups for the right
  22  *    sleeper state.
  23  *
  24  *  - the exclusive mode; because this requires preserving the list order
  25  *    and this is hard.
  26  *
  27  *  - custom wake functions; because you cannot give any guarantees about
  28  *    random code.
  29  *
  30  * As a side effect of this; the data structures are slimmer.
  31  *
  32  * One would recommend using this wait queue where possible.
  33  */
  34
  35 struct task_struct;
  36
  37 struct swait_queue_head {
  38         raw_spinlock_t          lock;
  39         struct list_head        task_list;
  40 };
  41
  42 struct swait_queue {
  43         struct task_struct      *task;
  44         struct list_head        task_list;
  45 };
  46
  47 #define __SWAITQUEUE_INITIALIZER(name) {                                \
  48         .task           = current,                                      \
  49         .task_list      = LIST_HEAD_INIT((name).task_list),             \
  50 }
  51
  52 #define DECLARE_SWAITQUEUE(name)                                        \
  53         struct swait_queue name = __SWAITQUEUE_INITIALIZER(name)
  54
  55 #define __SWAIT_QUEUE_HEAD_INITIALIZER(name) {                          \
  56         .lock           = __RAW_SPIN_LOCK_UNLOCKED(name.lock),          \
  57         .task_list      = LIST_HEAD_INIT((name).task_list),             \
  58 }
  59
  60 #define DECLARE_SWAIT_QUEUE_HEAD(name)                                  \
  61         struct swait_queue_head name = __SWAIT_QUEUE_HEAD_INITIALIZER(name)
  62
  63 extern void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
  64                                     struct lock_class_key *key);
  65
  66 #define init_swait_queue_head(q)                                \
  67         do {                                                    \
  68                 static struct lock_class_key __key;             \
  69                 __init_swait_queue_head((q), #q, &__key);       \
  70         } while (0)
  71
  72 #ifdef CONFIG_LOCKDEP
  73 # define __SWAIT_QUEUE_HEAD_INIT_ONSTACK(name)                  \
  74         ({ init_swait_queue_head(&name); name; })
  75 # define DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(name)                 \
  76         struct swait_queue_head name = __SWAIT_QUEUE_HEAD_INIT_ONSTACK(name)
  77 #else
  78 # define DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(name)                 \
  79         DECLARE_SWAIT_QUEUE_HEAD(name)
  80 #endif
  81
  82 static inline int swait_active(struct swait_queue_head *q)
  83 {
  84         return !list_empty(&q->task_list);
  85 }
  86
  87 extern void swake_up(struct swait_queue_head *q);
  88 extern void swake_up_all(struct swait_queue_head *q);
  89 extern void swake_up_locked(struct swait_queue_head *q);
  90
  91 extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
  92 extern void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state);
  93 extern long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state);
  94
  95 extern void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
  96 extern void finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
  97
  98 /* as per ___wait_event() but for swait, therefore "exclusive == 0" */
  99 #define ___swait_event(wq, condition, state, ret, cmd)                  \
 100 ({                                                                      \
 101         struct swait_queue __wait;                                      \
 102         long __ret = ret;                                               \
 103                                                                         \
 104         INIT_LIST_HEAD(&__wait.task_list);                              \
 105         for (;;) {                                                      \
 106                 long __int = prepare_to_swait_event(&wq, &__wait, state);\
 107                                                                         \
 108                 if (condition)                                          \
 109                         break;                                          \
 110                                                                         \
 111                 if (___wait_is_interruptible(state) && __int) {         \
 112                         __ret = __int;                                  \
 113                         break;                                          \
 114                 }                                                       \
 115                                                                         \
 116                 cmd;                                                    \
 117         }                                                               \
 118         finish_swait(&wq, &__wait);                                     \
 119         __ret;                                                          \
 120 })
 121
 122 #define __swait_event(wq, condition)                                    \
 123         (void)___swait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0,    \
 124                             schedule())
 125
 126 #define swait_event(wq, condition)                                      \
 127 do {                                                                    \
 128         if (condition)                                                  \
 129                 break;                                                  \
 130         __swait_event(wq, condition);                                   \
 131 } while (0)
 132
 133 #define __swait_event_timeout(wq, condition, timeout)                   \
 134         ___swait_event(wq, ___wait_cond_timeout(condition),             \
 135                       TASK_UNINTERRUPTIBLE, timeout,                    \
 136                       __ret = schedule_timeout(__ret))
 137
 138 #define swait_event_timeout(wq, condition, timeout)                     \
 139 ({                                                                      \
 140         long __ret = timeout;                                           \
 141         if (!___wait_cond_timeout(condition))                           \
 142                 __ret = __swait_event_timeout(wq, condition, timeout);  \
 143         __ret;                                                          \
 144 })
 145
 146 #define __swait_event_interruptible(wq, condition)                      \
 147         ___swait_event(wq, condition, TASK_INTERRUPTIBLE, 0,            \
 148                       schedule())
 149
 150 #define swait_event_interruptible(wq, condition)                        \
 151 ({                                                                      \
 152         int __ret = 0;                                                  \
 153         if (!(condition))                                               \
 154                 __ret = __swait_event_interruptible(wq, condition);     \
 155         __ret;                                                          \
 156 })
 157
 158 #define __swait_event_interruptible_timeout(wq, condition, timeout)     \
 159         ___swait_event(wq, ___wait_cond_timeout(condition),             \
 160                       TASK_INTERRUPTIBLE, timeout,                      \
 161                       __ret = schedule_timeout(__ret))
 162
 163 #define swait_event_interruptible_timeout(wq, condition, timeout)       \
 164 ({                                                                      \
 165         long __ret = timeout;                                           \
 166         if (!___wait_cond_timeout(condition))                           \
 167                 __ret = __swait_event_interruptible_timeout(wq,         \
 168                                                 condition, timeout);    \
 169         __ret;                                                          \
 170 })
 171
 172 #endif /* _LINUX_SWAIT_H */