Commit 401a8d04 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: cleanup flush/cancel functions 



Make the following cleanup changes.

* Relocate flush/cancel function prototypes and definitions.

* Relocate wait_on_cpu_work() and wait_on_work() before
  try_to_grab_pending().  These will be used to implement
  flush_work_sync().

* Make all flush/cancel functions return bool instead of int.

* Update wait_on_cpu_work() and wait_on_work() to return %true if they
  actually waited.

* Add / update comments.

This patch doesn't cause any functional changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 81dcaf65

include/linux/workqueue.h

+9 −9
Original line number Diff line number Diff line
@@ -343,7 +343,6 @@ extern int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, 


extern void flush_workqueue(struct workqueue_struct *wq);

extern void flush_scheduled_work(void);

extern void flush_delayed_work(struct delayed_work *work);



extern int schedule_work(struct work_struct *work);

extern int schedule_work_on(int cpu, struct work_struct *work);
@@ -355,8 +354,11 @@ extern int keventd_up(void); 


int execute_in_process_context(work_func_t fn, struct execute_work *);



extern int flush_work(struct work_struct *work);

extern int cancel_work_sync(struct work_struct *work);

extern bool flush_work(struct work_struct *work);

extern bool cancel_work_sync(struct work_struct *work);



extern bool flush_delayed_work(struct delayed_work *dwork);

extern bool cancel_delayed_work_sync(struct delayed_work *dwork);



extern void workqueue_set_max_active(struct workqueue_struct *wq,

				     int max_active);
@@ -370,9 +372,9 @@ extern unsigned int work_busy(struct work_struct *work); 
 * it returns 1 and the work doesn't re-arm itself. Run flush_workqueue() or

 * cancel_work_sync() to wait on it.

 */

static inline int cancel_delayed_work(struct delayed_work *work)

static inline bool cancel_delayed_work(struct delayed_work *work)

{

	int ret;

	bool ret;



	ret = del_timer_sync(&work->timer);

	if (ret)
@@ -385,9 +387,9 @@ static inline int cancel_delayed_work(struct delayed_work *work) 
 * if it returns 0 the timer function may be running and the queueing is in

 * progress.

 */

static inline int __cancel_delayed_work(struct delayed_work *work)

static inline bool __cancel_delayed_work(struct delayed_work *work)

{

	int ret;

	bool ret;



	ret = del_timer(&work->timer);

	if (ret)
@@ -395,8 +397,6 @@ static inline int __cancel_delayed_work(struct delayed_work *work) 
	return ret;

}



extern int cancel_delayed_work_sync(struct delayed_work *work);



/* Obsolete. use cancel_delayed_work_sync() */

static inline

void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,

kernel/workqueue.c

+94 −81
Original line number Diff line number Diff line
@@ -2327,16 +2327,24 @@ out_unlock: 
EXPORT_SYMBOL_GPL(flush_workqueue);



/**

 * flush_work - block until a work_struct's callback has terminated

 * @work: the work which is to be flushed

 * flush_work - wait for a work to finish executing the last queueing instance

 * @work: the work to flush

 *

 * Returns false if @work has already terminated.

 * Wait until @work has finished execution.  This function considers

 * only the last queueing instance of @work.  If @work has been

 * enqueued across different CPUs on a non-reentrant workqueue or on

 * multiple workqueues, @work might still be executing on return on

 * some of the CPUs from earlier queueing.

 *

 * It is expected that, prior to calling flush_work(), the caller has

 * arranged for the work to not be requeued, otherwise it doesn't make

 * sense to use this function.

 * If @work was queued only on a non-reentrant, ordered or unbound

 * workqueue, @work is guaranteed to be idle on return if it hasn't

 * been requeued since flush started.

 *

 * RETURNS:

 * %true if flush_work() waited for the work to finish execution,

 * %false if it was already idle.

 */

int flush_work(struct work_struct *work)

bool flush_work(struct work_struct *work)

{

	struct worker *worker = NULL;

	struct global_cwq *gcwq;
@@ -2374,13 +2382,49 @@ int flush_work(struct work_struct *work) 


	wait_for_completion(&barr.done);

	destroy_work_on_stack(&barr.work);

	return 1;

	return true;

already_gone:

	spin_unlock_irq(&gcwq->lock);

	return 0;

	return false;

}

EXPORT_SYMBOL_GPL(flush_work);



static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)

{

	struct wq_barrier barr;

	struct worker *worker;



	spin_lock_irq(&gcwq->lock);



	worker = find_worker_executing_work(gcwq, work);

	if (unlikely(worker))

		insert_wq_barrier(worker->current_cwq, &barr, work, worker);



	spin_unlock_irq(&gcwq->lock);



	if (unlikely(worker)) {

		wait_for_completion(&barr.done);

		destroy_work_on_stack(&barr.work);

		return true;

	} else

		return false;

}



static bool wait_on_work(struct work_struct *work)

{

	bool ret = false;

	int cpu;



	might_sleep();



	lock_map_acquire(&work->lockdep_map);

	lock_map_release(&work->lockdep_map);



	for_each_gcwq_cpu(cpu)

		ret |= wait_on_cpu_work(get_gcwq(cpu), work);

	return ret;

}



/*

 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,

 * so this work can't be re-armed in any way.
@@ -2423,39 +2467,7 @@ static int try_to_grab_pending(struct work_struct *work) 
	return ret;

}



static void wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)

{

	struct wq_barrier barr;

	struct worker *worker;



	spin_lock_irq(&gcwq->lock);



	worker = find_worker_executing_work(gcwq, work);

	if (unlikely(worker))

		insert_wq_barrier(worker->current_cwq, &barr, work, worker);



	spin_unlock_irq(&gcwq->lock);



	if (unlikely(worker)) {

		wait_for_completion(&barr.done);

		destroy_work_on_stack(&barr.work);

	}

}



static void wait_on_work(struct work_struct *work)

{

	int cpu;



	might_sleep();



	lock_map_acquire(&work->lockdep_map);

	lock_map_release(&work->lockdep_map);



	for_each_gcwq_cpu(cpu)

		wait_on_cpu_work(get_gcwq(cpu), work);

}



static int __cancel_work_timer(struct work_struct *work,

static bool __cancel_work_timer(struct work_struct *work,

				struct timer_list* timer)

{

	int ret;
@@ -2472,42 +2484,60 @@ static int __cancel_work_timer(struct work_struct *work, 
}



/**

 * cancel_work_sync - block until a work_struct's callback has terminated

 * @work: the work which is to be flushed

 *

 * Returns true if @work was pending.

 * cancel_work_sync - cancel a work and wait for it to finish

 * @work: the work to cancel

 *

 * cancel_work_sync() will cancel the work if it is queued. If the work's

 * callback appears to be running, cancel_work_sync() will block until it

 * has completed.

 * Cancel @work and wait for its execution to finish.  This function

 * can be used even if the work re-queues itself or migrates to

 * another workqueue.  On return from this function, @work is

 * guaranteed to be not pending or executing on any CPU.

 *

 * It is possible to use this function if the work re-queues itself. It can

 * cancel the work even if it migrates to another workqueue, however in that

 * case it only guarantees that work->func() has completed on the last queued

 * workqueue.

 *

 * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not

 * pending, otherwise it goes into a busy-wait loop until the timer expires.

 * cancel_work_sync(&delayed_work->work) must not be used for

 * delayed_work's.  Use cancel_delayed_work_sync() instead.

 *

 * The caller must ensure that workqueue_struct on which this work was last

 * The caller must ensure that the workqueue on which @work was last

 * queued can't be destroyed before this function returns.

 *

 * RETURNS:

 * %true if @work was pending, %false otherwise.

 */

int cancel_work_sync(struct work_struct *work)

bool cancel_work_sync(struct work_struct *work)

{

	return __cancel_work_timer(work, NULL);

}

EXPORT_SYMBOL_GPL(cancel_work_sync);



/**

 * cancel_delayed_work_sync - reliably kill off a delayed work.

 * @dwork: the delayed work struct

 * flush_delayed_work - wait for a dwork to finish executing the last queueing

 * @dwork: the delayed work to flush

 *

 * Returns true if @dwork was pending.

 * Delayed timer is cancelled and the pending work is queued for

 * immediate execution.  Like flush_work(), this function only

 * considers the last queueing instance of @dwork.

 *

 * It is possible to use this function if @dwork rearms itself via queue_work()

 * or queue_delayed_work(). See also the comment for cancel_work_sync().

 * RETURNS:

 * %true if flush_work() waited for the work to finish execution,

 * %false if it was already idle.

 */

int cancel_delayed_work_sync(struct delayed_work *dwork)

bool flush_delayed_work(struct delayed_work *dwork)

{

	if (del_timer_sync(&dwork->timer))

		__queue_work(raw_smp_processor_id(),

			     get_work_cwq(&dwork->work)->wq, &dwork->work);

	return flush_work(&dwork->work);

}

EXPORT_SYMBOL(flush_delayed_work);



/**

 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish

 * @dwork: the delayed work cancel

 *

 * This is cancel_work_sync() for delayed works.

 *

 * RETURNS:

 * %true if @dwork was pending, %false otherwise.

 */

bool cancel_delayed_work_sync(struct delayed_work *dwork)

{

	return __cancel_work_timer(&dwork->work, &dwork->timer);

}
@@ -2558,23 +2588,6 @@ int schedule_delayed_work(struct delayed_work *dwork, 
}

EXPORT_SYMBOL(schedule_delayed_work);



/**

 * flush_delayed_work - block until a dwork_struct's callback has terminated

 * @dwork: the delayed work which is to be flushed

 *

 * Any timeout is cancelled, and any pending work is run immediately.

 */

void flush_delayed_work(struct delayed_work *dwork)

{

	if (del_timer_sync(&dwork->timer)) {

		__queue_work(get_cpu(), get_work_cwq(&dwork->work)->wq,

			     &dwork->work);

		put_cpu();

	}

	flush_work(&dwork->work);

}

EXPORT_SYMBOL(flush_delayed_work);



/**

 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay

 * @cpu: cpu to use

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