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workqueue: drop WQ_RESCUER and test workqueue->rescuer for NULL instead 

WQ_RESCUER is superflous.  WQ_MEM_RECLAIM indicates that the user
wants a rescuer and testing wq->rescuer for NULL can answer whether a
given workqueue has a rescuer or not.  Drop WQ_RESCUER and test
wq->rescuer directly.

This will help simplifying __alloc_workqueue_key() failure path by
allowing it to use destroy_workqueue() on a partially constructed
workqueue, which in turn will help implementing dynamic management of
pool_workqueues.

While at it, clear wq->rescuer after freeing it in
destroy_workqueue().  This is a precaution as scheduled changes will
make destruction more complex.

This patch doesn't introduce any functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-03-12 11:30:03 -07:00
parent ac6104cdf8
commit 493008a8e4
2 changed files with 10 additions and 13 deletions
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1
include/linux/workqueue.h
View File

@ -295,7 +295,6 @@ enum {
WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */
WQ_DRAINING = 1 << 6, /* internal: workqueue is draining */
WQ_RESCUER = 1 << 7, /* internal: workqueue has rescuer */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */

22
kernel/workqueue.c
View File

@ -1827,7 +1827,7 @@ static void send_mayday(struct work_struct *work)
lockdep_assert_held(&workqueue_lock);
if (!(wq->flags & WQ_RESCUER))
if (!wq->rescuer)
return;
/* mayday mayday mayday */
@ -2285,7 +2285,7 @@ sleep:
* @__rescuer: self
*
* Workqueue rescuer thread function. There's one rescuer for each
* workqueue which has WQ_RESCUER set.
* workqueue which has WQ_MEM_RECLAIM set.
*
* Regular work processing on a pool may block trying to create a new
* worker which uses GFP_KERNEL allocation which has slight chance of
@ -2769,7 +2769,7 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
* flusher is not running on the same workqueue by verifying write
* access.
*/
if (pwq->wq->saved_max_active == 1 || pwq->wq->flags & WQ_RESCUER)
if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
lock_map_acquire(&pwq->wq->lockdep_map);
else
lock_map_acquire_read(&pwq->wq->lockdep_map);
@ -3412,13 +3412,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
va_end(args);
va_end(args1);
/*
* Workqueues which may be used during memory reclaim should
* have a rescuer to guarantee forward progress.
*/
if (flags & WQ_MEM_RECLAIM)
flags |= WQ_RESCUER;
max_active = max_active ?: WQ_DFL_ACTIVE;
max_active = wq_clamp_max_active(max_active, flags, wq->name);
@ -3449,7 +3442,11 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
}
local_irq_enable();
if (flags & WQ_RESCUER) {
/*
* Workqueues which may be used during memory reclaim should
* have a rescuer to guarantee forward progress.
*/
if (flags & WQ_MEM_RECLAIM) {
struct worker *rescuer;
wq->rescuer = rescuer = alloc_worker();
@ -3533,9 +3530,10 @@ void destroy_workqueue(struct workqueue_struct *wq)
spin_unlock_irq(&workqueue_lock);
if (wq->flags & WQ_RESCUER) {
if (wq->rescuer) {
kthread_stop(wq->rescuer->task);
kfree(wq->rescuer);
wq->rescuer = NULL;
}
/*