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workqueue: perform non-reentrancy test when queueing to unbound workqueues too 

Because per-cpu workqueues have multiple pwqs (pool_workqueues) to
serve the CPUs, to guarantee that a single work item isn't queued on
one pwq while still executing another, __queue_work() takes a look at
the previous pool the target work item was on and if it's still
executing there, queue the work item on that pool.

To support changing workqueue_attrs on the fly, unbound workqueues too
will have multiple pwqs and thus need non-reentrancy test when
queueing.  This patch modifies __queue_work() such that the reentrancy
test is performed regardless of the workqueue type.

per_cpu_ptr(wq->cpu_pwqs, cpu) used to be used to determine the
matching pwq for the last pool.  This can't be used for unbound
workqueues and is replaced with worker->current_pwq which also happens
to be simpler.

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 11:30:04 -07:00
parent 75ccf5950f
commit c9178087ac
1 changed files with 19 additions and 23 deletions
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42
kernel/workqueue.c
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@ -1209,6 +1209,7 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
struct pool_workqueue *pwq;
struct worker_pool *last_pool;
struct list_head *worklist;
unsigned int work_flags;
unsigned int req_cpu = cpu;
@ -1228,41 +1229,36 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
WARN_ON_ONCE(!is_chained_work(wq)))
return;
/* determine the pwq to use */
/* pwq which will be used unless @work is executing elsewhere */
if (!(wq->flags & WQ_UNBOUND)) {
struct worker_pool *last_pool;
if (cpu == WORK_CPU_UNBOUND)
cpu = raw_smp_processor_id();
/*
* It's multi cpu. If @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-reentrancy.
*/
pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
last_pool = get_work_pool(work);
} else {
pwq = first_pwq(wq);
}
if (last_pool && last_pool != pwq->pool) {
struct worker *worker;
/*
* If @work was previously on a different pool, it might still be
* running there, in which case the work needs to be queued on that
* pool to guarantee non-reentrancy.
*/
last_pool = get_work_pool(work);
if (last_pool && last_pool != pwq->pool) {
struct worker *worker;
spin_lock(&last_pool->lock);
spin_lock(&last_pool->lock);
worker = find_worker_executing_work(last_pool, work);
worker = find_worker_executing_work(last_pool, work);
if (worker && worker->current_pwq->wq == wq) {
pwq = per_cpu_ptr(wq->cpu_pwqs, last_pool->cpu);
} else {
/* meh... not running there, queue here */
spin_unlock(&last_pool->lock);
spin_lock(&pwq->pool->lock);
}
if (worker && worker->current_pwq->wq == wq) {
pwq = worker->current_pwq;
} else {
/* meh... not running there, queue here */
spin_unlock(&last_pool->lock);
spin_lock(&pwq->pool->lock);
}
} else {
pwq = first_pwq(wq);
spin_lock(&pwq->pool->lock);
}