From eef6a7d5c2f38adadab8240fabf43730fe796482 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 12 Feb 2010 17:39:21 +0900 Subject: workqueue: warn about flush_scheduled_work() This patch (as1319) adds kerneldoc and a pointed warning to flush_scheduled_work(). Signed-off-by: Alan Stern Signed-off-by: Tejun Heo diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5bfb213..0225fea8 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -845,6 +845,30 @@ int schedule_on_each_cpu(work_func_t func) return 0; } +/** + * flush_scheduled_work - ensure that any scheduled work has run to completion. + * + * Forces execution of the kernel-global workqueue and blocks until its + * completion. + * + * Think twice before calling this function! It's very easy to get into + * trouble if you don't take great care. Either of the following situations + * will lead to deadlock: + * + * One of the work items currently on the workqueue needs to acquire + * a lock held by your code or its caller. + * + * Your code is running in the context of a work routine. + * + * They will be detected by lockdep when they occur, but the first might not + * occur very often. It depends on what work items are on the workqueue and + * what locks they need, which you have no control over. + * + * In most situations flushing the entire workqueue is overkill; you merely + * need to know that a particular work item isn't queued and isn't running. + * In such cases you should use cancel_delayed_work_sync() or + * cancel_work_sync() instead. + */ void flush_scheduled_work(void) { flush_workqueue(keventd_wq); -- cgit v0.10.2