Commit 50816c48 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

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: default avatarIngo Molnar <mingo@kernel.org>
parent ac6424b9

include/linux/wait.h

+42 −42
Original line number Diff line number Diff line
@@ -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

+49 −49
Original line number Diff line number Diff line
@@ -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);

}



/*

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