LXR linux/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
  35struct task_struct;
  36
  37struct swait_queue_head {
  38        raw_spinlock_t          lock;
  39        struct list_head        task_list;
  40};
  41
  42struct 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
  63extern 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
  82static inline int swait_active(struct swait_queue_head *q)
  83{
  84        return !list_empty(&q->task_list);
  85}
  86
  87extern void swake_up(struct swait_queue_head *q);
  88extern void swake_up_all(struct swait_queue_head *q);
  89extern void swake_up_locked(struct swait_queue_head *q);
  90
  91extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
  92extern void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state);
  93extern long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state);
  94
  95extern void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
  96extern 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)                                      \
 127do {                                                                    \
 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 */
 173