sched/wait: Standardize internal naming of wait-queue entries

So the various wait-queue entry variables in include/linux/wait.h
and kernel/sched/wait.c are named in a colorfully inconsistent
way:

	wait_queue_entry_t *wait
	wait_queue_entry_t *__wait	(even in plain C code!)
	wait_queue_entry_t *q		(!)
	wait_queue_entry_t *new		(making anyone who knows C++ cringe)
	wait_queue_entry_t *old

I think part of the reason for the inconsistency is the constant
apparent confusion about what a wait queue 'head' versus 'entry' is.

( Some of the documentation talks about a 'wait descriptor', which is
  the wait-queue entry itself - further adding to the confusion. )

The most common name is 'wait', but that in itself is somewhat
ambiguous as well, as it does not really make it clear whether
it's a wait-queue entry or head.

To improve all this name the wait-queue entry structure parameters
and variables consistently and push through this naming into all
the wait.h and wait.c code:

	struct wait_queue_entry *wq_entry

The 'wq_' prefix makes it easy to grep for, and we also use the
opportunity to move away from the typedef to a plain 'struct' naming:
in the kernel we typically reserve typedefs for cases where a
C structure is really small and somewhat opaque - such as pte_t.

wait-queue entries are neither small nor opaque, so use the more
standard 'struct xxx_entry' list management code nomenclature instead.

( We don't touch external users, and we preserve the typedef as well
  for actual wait-queue users, to reduce unnecessary churn. )

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 5889f0c86ff706d343ec8275f444f9606abf67e8..77fdea851d8b4013a9f060b19eacc3f2ad67aa5a 100644 (file)
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -11,8 +11,9 @@
 #include <uapi/linux/wait.h>
 
 typedef struct wait_queue_entry wait_queue_entry_t;
-typedef int (*wait_queue_func_t)(wait_queue_entry_t *wait, unsigned mode, int flags, void *key);
-int default_wake_function(wait_queue_entry_t *wait, unsigned mode, int flags, void *key);
+
+typedef int (*wait_queue_func_t)(struct wait_queue_entry *wq_entry, unsigned mode, int flags, void *key);
+int default_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int flags, void *key);
 
 /* wait_queue_entry::flags */
 #define WQ_FLAG_EXCLUSIVE      0x01
@@ -37,7 +38,7 @@ struct wait_bit_key {
 
 struct wait_bit_queue {
        struct wait_bit_key     key;
-       wait_queue_entry_t      wait;
+       struct wait_queue_entry wait;
 };
 
 struct __wait_queue_head {
@@ -58,7 +59,7 @@ struct task_struct;
        .task_list      = { NULL, NULL } }
 
 #define DECLARE_WAITQUEUE(name, tsk)                                   \
-       wait_queue_entry_t name = __WAITQUEUE_INITIALIZER(name, tsk)
+       struct wait_queue_entry name = __WAITQUEUE_INITIALIZER(name, tsk)
 
 #define __WAIT_QUEUE_HEAD_INITIALIZER(name) {                          \
        .lock           = __SPIN_LOCK_UNLOCKED(name.lock),              \
@@ -91,19 +92,19 @@ extern void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct
 # define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) DECLARE_WAIT_QUEUE_HEAD(name)
 #endif
 
-static inline void init_waitqueue_entry(wait_queue_entry_t *q, struct task_struct *p)
+static inline void init_waitqueue_entry(struct wait_queue_entry *wq_entry, struct task_struct *p)
 {
-       q->flags        = 0;
-       q->private      = p;
-       q->func         = default_wake_function;
+       wq_entry->flags         = 0;
+       wq_entry->private       = p;
+       wq_entry->func          = default_wake_function;
 }
 
 static inline void
-init_waitqueue_func_entry(wait_queue_entry_t *q, wait_queue_func_t func)
+init_waitqueue_func_entry(struct wait_queue_entry *wq_entry, wait_queue_func_t func)
 {
-       q->flags        = 0;
-       q->private      = NULL;
-       q->func         = func;
+       wq_entry->flags         = 0;
+       wq_entry->private       = NULL;
+       wq_entry->func          = func;
 }
 
 /**
@@ -162,42 +163,41 @@ static inline bool wq_has_sleeper(wait_queue_head_t *wq)
        return waitqueue_active(wq);
 }
 
-extern void add_wait_queue(wait_queue_head_t *q, wait_queue_entry_t *wait);
-extern void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_entry_t *wait);
-extern void remove_wait_queue(wait_queue_head_t *q, wait_queue_entry_t *wait);
+extern void add_wait_queue(wait_queue_head_t *q, struct wait_queue_entry *wq_entry);
+extern void add_wait_queue_exclusive(wait_queue_head_t *q, struct wait_queue_entry *wq_entry);
+extern void remove_wait_queue(wait_queue_head_t *q, struct wait_queue_entry *wq_entry);
 
-static inline void __add_wait_queue(wait_queue_head_t *head, wait_queue_entry_t *new)
+static inline void __add_wait_queue(wait_queue_head_t *head, struct wait_queue_entry *wq_entry)
 {
-       list_add(&new->task_list, &head->task_list);
+       list_add(&wq_entry->task_list, &head->task_list);
 }
 
 /*
  * Used for wake-one threads:
  */
 static inline void
-__add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_entry_t *wait)
+__add_wait_queue_exclusive(wait_queue_head_t *q, struct wait_queue_entry *wq_entry)
 {
-       wait->flags |= WQ_FLAG_EXCLUSIVE;
-       __add_wait_queue(q, wait);
+       wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
+       __add_wait_queue(q, wq_entry);
 }
 
-static inline void __add_wait_queue_entry_tail(wait_queue_head_t *head,
-                                        wait_queue_entry_t *new)
+static inline void __add_wait_queue_entry_tail(wait_queue_head_t *head, struct wait_queue_entry *wq_entry)
 {
-       list_add_tail(&new->task_list, &head->task_list);
+       list_add_tail(&wq_entry->task_list, &head->task_list);
 }
 
 static inline void
-__add_wait_queue_entry_tail_exclusive(wait_queue_head_t *q, wait_queue_entry_t *wait)
+__add_wait_queue_entry_tail_exclusive(wait_queue_head_t *q, struct wait_queue_entry *wq_entry)
 {
-       wait->flags |= WQ_FLAG_EXCLUSIVE;
-       __add_wait_queue_entry_tail(q, wait);
+       wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
+       __add_wait_queue_entry_tail(q, wq_entry);
 }
 
 static inline void
-__remove_wait_queue(wait_queue_head_t *head, wait_queue_entry_t *old)
+__remove_wait_queue(wait_queue_head_t *head, struct wait_queue_entry *wq_entry)
 {
-       list_del(&old->task_list);
+       list_del(&wq_entry->task_list);
 }
 
 typedef int wait_bit_action_f(struct wait_bit_key *, int mode);
@@ -252,7 +252,7 @@ wait_queue_head_t *bit_waitqueue(void *, int);
        (!__builtin_constant_p(state) ||                                \
                state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)  \
 
-extern void init_wait_entry(wait_queue_entry_t *__wait, int flags);
+extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);
 
 /*
  * The below macro ___wait_event() has an explicit shadow of the __ret
@@ -269,12 +269,12 @@ extern void init_wait_entry(wait_queue_entry_t *__wait, int flags);
 #define ___wait_event(wq, condition, state, exclusive, ret, cmd)       \
 ({                                                                     \
        __label__ __out;                                                \
-       wait_queue_entry_t __wait;                                              \
+       struct wait_queue_entry __wq_entry;                             \
        long __ret = ret;       /* explicit shadow */                   \
                                                                        \
-       init_wait_entry(&__wait, exclusive ? WQ_FLAG_EXCLUSIVE : 0);    \
+       init_wait_entry(&__wq_entry, exclusive ? WQ_FLAG_EXCLUSIVE : 0);\
        for (;;) {                                                      \
-               long __int = prepare_to_wait_event(&wq, &__wait, state);\
+               long __int = prepare_to_wait_event(&wq, &__wq_entry, state);\
                                                                        \
                if (condition)                                          \
                        break;                                          \
@@ -286,7 +286,7 @@ extern void init_wait_entry(wait_queue_entry_t *__wait, int flags);
                                                                        \
                cmd;                                                    \
        }                                                               \
-       finish_wait(&wq, &__wait);                                      \
+       finish_wait(&wq, &__wq_entry);                                  \
 __out: __ret;                                                          \
 })
 
@@ -970,17 +970,17 @@ do {                                                                      \
 /*
  * Waitqueues which are removed from the waitqueue_head at wakeup time
  */
-void prepare_to_wait(wait_queue_head_t *q, wait_queue_entry_t *wait, int state);
-void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_entry_t *wait, int state);
-long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_entry_t *wait, int state);
-void finish_wait(wait_queue_head_t *q, wait_queue_entry_t *wait);
-long wait_woken(wait_queue_entry_t *wait, unsigned mode, long timeout);
-int woken_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key);
-int autoremove_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key);
-int wake_bit_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key);
+void prepare_to_wait(wait_queue_head_t *q, struct wait_queue_entry *wq_entry, int state);
+void prepare_to_wait_exclusive(wait_queue_head_t *q, struct wait_queue_entry *wq_entry, int state);
+long prepare_to_wait_event(wait_queue_head_t *q, struct wait_queue_entry *wq_entry, int state);
+void finish_wait(wait_queue_head_t *q, struct wait_queue_entry *wq_entry);
+long wait_woken(struct wait_queue_entry *wq_entry, unsigned mode, long timeout);
+int woken_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key);
+int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key);
+int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key);
 
 #define DEFINE_WAIT_FUNC(name, function)                               \
-       wait_queue_entry_t name = {                                     \
+       struct wait_queue_entry name = {                                \
                .private        = current,                              \
                .func           = function,                             \
                .task_list      = LIST_HEAD_INIT((name).task_list),     \

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 301ea02dede0489d870019c27bd7da7a9b5a4c2d..c37b3140763ebc919422969dd8303df3457ff8b6 100644 (file)
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -21,34 +21,34 @@ void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_c
 
 EXPORT_SYMBOL(__init_waitqueue_head);
 
-void add_wait_queue(wait_queue_head_t *q, wait_queue_entry_t *wait)
+void add_wait_queue(wait_queue_head_t *q, struct wait_queue_entry *wq_entry)
 {
        unsigned long flags;
 
-       wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+       wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
        spin_lock_irqsave(&q->lock, flags);
-       __add_wait_queue(q, wait);
+       __add_wait_queue_entry_tail(q, wq_entry);
        spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL(add_wait_queue);
 
-void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_entry_t *wait)
+void add_wait_queue_exclusive(wait_queue_head_t *q, struct wait_queue_entry *wq_entry)
 {
        unsigned long flags;
 
-       wait->flags |= WQ_FLAG_EXCLUSIVE;
+       wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
        spin_lock_irqsave(&q->lock, flags);
-       __add_wait_queue_entry_tail(q, wait);
+       __add_wait_queue_entry_tail(q, wq_entry);
        spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL(add_wait_queue_exclusive);
 
-void remove_wait_queue(wait_queue_head_t *q, wait_queue_entry_t *wait)
+void remove_wait_queue(wait_queue_head_t *q, struct wait_queue_entry *wq_entry)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&q->lock, flags);
-       __remove_wait_queue(q, wait);
+       __remove_wait_queue(q, wq_entry);
        spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL(remove_wait_queue);
@@ -170,43 +170,43 @@ EXPORT_SYMBOL_GPL(__wake_up_sync);        /* For internal use only */
  * loads to move into the critical region).
  */
 void
-prepare_to_wait(wait_queue_head_t *q, wait_queue_entry_t *wait, int state)
+prepare_to_wait(wait_queue_head_t *q, struct wait_queue_entry *wq_entry, int state)
 {
        unsigned long flags;
 
-       wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+       wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
        spin_lock_irqsave(&q->lock, flags);
-       if (list_empty(&wait->task_list))
-               __add_wait_queue(q, wait);
+       if (list_empty(&wq_entry->task_list))
+               __add_wait_queue(q, wq_entry);
        set_current_state(state);
        spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL(prepare_to_wait);
 
 void
-prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_entry_t *wait, int state)
+prepare_to_wait_exclusive(wait_queue_head_t *q, struct wait_queue_entry *wq_entry, int state)
 {
        unsigned long flags;
 
-       wait->flags |= WQ_FLAG_EXCLUSIVE;
+       wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
        spin_lock_irqsave(&q->lock, flags);
-       if (list_empty(&wait->task_list))
-               __add_wait_queue_entry_tail(q, wait);
+       if (list_empty(&wq_entry->task_list))
+               __add_wait_queue_entry_tail(q, wq_entry);
        set_current_state(state);
        spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL(prepare_to_wait_exclusive);
 
-void init_wait_entry(wait_queue_entry_t *wait, int flags)
+void init_wait_entry(struct wait_queue_entry *wq_entry, int flags)
 {
-       wait->flags = flags;
-       wait->private = current;
-       wait->func = autoremove_wake_function;
-       INIT_LIST_HEAD(&wait->task_list);
+       wq_entry->flags = flags;
+       wq_entry->private = current;
+       wq_entry->func = autoremove_wake_function;
+       INIT_LIST_HEAD(&wq_entry->task_list);
 }
 EXPORT_SYMBOL(init_wait_entry);
 
-long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_entry_t *wait, int state)
+long prepare_to_wait_event(wait_queue_head_t *q, struct wait_queue_entry *wq_entry, int state)
 {
        unsigned long flags;
        long ret = 0;
@@ -225,14 +225,14 @@ long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_entry_t *wait, int s
                 * can't see us, it should wake up another exclusive waiter if
                 * we fail.
                 */
-               list_del_init(&wait->task_list);
+               list_del_init(&wq_entry->task_list);
                ret = -ERESTARTSYS;
        } else {
-               if (list_empty(&wait->task_list)) {
-                       if (wait->flags & WQ_FLAG_EXCLUSIVE)
-                               __add_wait_queue_entry_tail(q, wait);
+               if (list_empty(&wq_entry->task_list)) {
+                       if (wq_entry->flags & WQ_FLAG_EXCLUSIVE)
+                               __add_wait_queue_entry_tail(q, wq_entry);
                        else
-                               __add_wait_queue(q, wait);
+                               __add_wait_queue(q, wq_entry);
                }
                set_current_state(state);
        }
@@ -284,13 +284,13 @@ EXPORT_SYMBOL(do_wait_intr_irq);
 /**
  * finish_wait - clean up after waiting in a queue
  * @q: waitqueue waited on
- * @wait: wait descriptor
+ * @wq_entry: wait descriptor
  *
  * Sets current thread back to running state and removes
  * the wait descriptor from the given waitqueue if still
  * queued.
  */
-void finish_wait(wait_queue_head_t *q, wait_queue_entry_t *wait)
+void finish_wait(wait_queue_head_t *q, struct wait_queue_entry *wq_entry)
 {
        unsigned long flags;
 
@@ -308,20 +308,20 @@ void finish_wait(wait_queue_head_t *q, wait_queue_entry_t *wait)
         *    have _one_ other CPU that looks at or modifies
         *    the list).
         */
-       if (!list_empty_careful(&wait->task_list)) {
+       if (!list_empty_careful(&wq_entry->task_list)) {
                spin_lock_irqsave(&q->lock, flags);
-               list_del_init(&wait->task_list);
+               list_del_init(&wq_entry->task_list);
                spin_unlock_irqrestore(&q->lock, flags);
        }
 }
 EXPORT_SYMBOL(finish_wait);
 
-int autoremove_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
+int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key)
 {
-       int ret = default_wake_function(wait, mode, sync, key);
+       int ret = default_wake_function(wq_entry, mode, sync, key);
 
        if (ret)
-               list_del_init(&wait->task_list);
+               list_del_init(&wq_entry->task_list);
        return ret;
 }
 EXPORT_SYMBOL(autoremove_wake_function);
@@ -341,17 +341,17 @@ static inline bool is_kthread_should_stop(void)
  *
  *     p->state = mode;                                condition = true;
  *     smp_mb(); // A                          smp_wmb(); // C
- *     if (!wait->flags & WQ_FLAG_WOKEN)       wait->flags |= WQ_FLAG_WOKEN;
+ *     if (!wq_entry->flags & WQ_FLAG_WOKEN)   wq_entry->flags |= WQ_FLAG_WOKEN;
  *         schedule()                          try_to_wake_up();
  *     p->state = TASK_RUNNING;                    ~~~~~~~~~~~~~~~~~~
- *     wait->flags &= ~WQ_FLAG_WOKEN;          condition = true;
+ *     wq_entry->flags &= ~WQ_FLAG_WOKEN;              condition = true;
  *     smp_mb() // B                           smp_wmb(); // C
- *                                             wait->flags |= WQ_FLAG_WOKEN;
+ *                                             wq_entry->flags |= WQ_FLAG_WOKEN;
  * }
  * remove_wait_queue(&wq, &wait);
  *
  */
-long wait_woken(wait_queue_entry_t *wait, unsigned mode, long timeout)
+long wait_woken(struct wait_queue_entry *wq_entry, unsigned mode, long timeout)
 {
        set_current_state(mode); /* A */
        /*
@@ -359,7 +359,7 @@ long wait_woken(wait_queue_entry_t *wait, unsigned mode, long timeout)
         * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
         * also observe all state before the wakeup.
         */
-       if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
+       if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
                timeout = schedule_timeout(timeout);
        __set_current_state(TASK_RUNNING);
 
@@ -369,13 +369,13 @@ long wait_woken(wait_queue_entry_t *wait, unsigned mode, long timeout)
         * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss
         * an event.
         */
-       smp_store_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */
+       smp_store_mb(wq_entry->flags, wq_entry->flags & ~WQ_FLAG_WOKEN); /* B */
 
        return timeout;
 }
 EXPORT_SYMBOL(wait_woken);
 
-int woken_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
+int woken_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key)
 {
        /*
         * Although this function is called under waitqueue lock, LOCK
@@ -385,24 +385,24 @@ int woken_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void
         * and is paired with smp_store_mb() in wait_woken().
         */
        smp_wmb(); /* C */
-       wait->flags |= WQ_FLAG_WOKEN;
+       wq_entry->flags |= WQ_FLAG_WOKEN;
 
-       return default_wake_function(wait, mode, sync, key);
+       return default_wake_function(wq_entry, mode, sync, key);
 }
 EXPORT_SYMBOL(woken_wake_function);
 
-int wake_bit_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
+int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg)
 {
        struct wait_bit_key *key = arg;
        struct wait_bit_queue *wait_bit
-               = container_of(wait, struct wait_bit_queue, wait);
+               = container_of(wq_entry, struct wait_bit_queue, wait);
 
        if (wait_bit->key.flags != key->flags ||
                        wait_bit->key.bit_nr != key->bit_nr ||
                        test_bit(key->bit_nr, key->flags))
                return 0;
        else
-               return autoremove_wake_function(wait, mode, sync, key);
+               return autoremove_wake_function(wq_entry, mode, sync, key);
 }
 EXPORT_SYMBOL(wake_bit_function);
 
@@ -534,19 +534,19 @@ static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
        return bit_waitqueue(p, 0);
 }
 
-static int wake_atomic_t_function(wait_queue_entry_t *wait, unsigned mode, int sync,
+static int wake_atomic_t_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync,
                                  void *arg)
 {
        struct wait_bit_key *key = arg;
        struct wait_bit_queue *wait_bit
-               = container_of(wait, struct wait_bit_queue, wait);
+               = container_of(wq_entry, struct wait_bit_queue, wait);
        atomic_t *val = key->flags;
 
        if (wait_bit->key.flags != key->flags ||
            wait_bit->key.bit_nr != key->bit_nr ||
            atomic_read(val) != 0)
                return 0;
-       return autoremove_wake_function(wait, mode, sync, key);
+       return autoremove_wake_function(wq_entry, mode, sync, key);
 }
 
 /*