From c9178087acd71b4ea010ea48e147cf66952d2da9 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 12 Mar 2013 11:30:04 -0700 Subject: [PATCH] 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 Reviewed-by: Lai Jiangshan --- kernel/workqueue.c | 42 +++++++++++++++++++----------------------- 1 file changed, 19 insertions(+), 23 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index e933979678e5..16fb6747276a 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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); }