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: NIngo Molnar <mingo@kernel.org>

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),	\

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);
 }
 
 /*