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workqueue: implement WQ_NON_REENTRANT 

With gcwq managing all the workers and work->data pointing to the last
gcwq it was on, non-reentrance can be easily implemented by checking
whether the work is still running on the previous gcwq on queueing.
Implement it.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2010-06-29 10:07:13 +02:00
parent 7a22ad757e
commit 18aa9effad
2 changed files with 30 additions and 3 deletions
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1
include/linux/workqueue.h
View File

@ -225,6 +225,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
enum {
WQ_FREEZEABLE = 1 << 0, /* freeze during suspend */
WQ_SINGLE_CPU = 1 << 1, /* only single cpu at a time */
WQ_NON_REENTRANT = 1 << 2, /* guarantee non-reentrance */
};
extern struct workqueue_struct *

32
kernel/workqueue.c
View File

@ -534,11 +534,37 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
debug_work_activate(work);
/* determine gcwq to use */
/*
* Determine gcwq to use. SINGLE_CPU is inherently
* NON_REENTRANT, so test it first.
*/
if (!(wq->flags & WQ_SINGLE_CPU)) {
/* just use the requested cpu for multicpu workqueues */
struct global_cwq *last_gcwq;
/*
* It's multi cpu. If @wq is non-reentrant and @work
* was previously on a different cpu, it might still
* be running there, in which case the work needs to
* be queued on that cpu to guarantee non-reentrance.
*/
gcwq = get_gcwq(cpu);
spin_lock_irqsave(&gcwq->lock, flags);
if (wq->flags & WQ_NON_REENTRANT &&
(last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
struct worker *worker;
spin_lock_irqsave(&last_gcwq->lock, flags);
worker = find_worker_executing_work(last_gcwq, work);
if (worker && worker->current_cwq->wq == wq)
gcwq = last_gcwq;
else {
/* meh... not running there, queue here */
spin_unlock_irqrestore(&last_gcwq->lock, flags);
spin_lock_irqsave(&gcwq->lock, flags);
}
} else
spin_lock_irqsave(&gcwq->lock, flags);
} else {
unsigned int req_cpu = cpu;