From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id AD348828DF for ; Thu, 14 Apr 2016 11:15:20 -0400 (EDT) Received: by mail-lf0-f71.google.com with SMTP id k200so48867875lfg.1 for ; Thu, 14 Apr 2016 08:15:20 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id kq8si45785598wjc.2.2016.04.14.08.15.19 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 14 Apr 2016 08:15:19 -0700 (PDT) From: Petr Mladek Subject: [PATCH v6 04/20] kthread: Add drain_kthread_worker() Date: Thu, 14 Apr 2016 17:14:23 +0200 Message-Id: <1460646879-617-5-git-send-email-pmladek@suse.com> In-Reply-To: <1460646879-617-1-git-send-email-pmladek@suse.com> References: <1460646879-617-1-git-send-email-pmladek@suse.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Oleg Nesterov , Tejun Heo , Ingo Molnar , Peter Zijlstra Cc: Steven Rostedt , "Paul E. McKenney" , Josh Triplett , Thomas Gleixner , Linus Torvalds , Jiri Kosina , Borislav Petkov , Michal Hocko , linux-mm@kvack.org, Vlastimil Babka , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Mladek flush_kthread_worker() returns when the currently queued works are proceed. But some other works might have been queued in the meantime. This patch adds drain_kthread_worker() that is inspired by drain_workqueue(). It returns when the queue is completely empty and warns when it takes too long. The initial implementation does not block queuing new works when draining. It makes things much easier. The blocking would be useful to debug potential problems but it is not clear if it is worth the complication at the moment. Signed-off-by: Petr Mladek --- kernel/kthread.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/kernel/kthread.c b/kernel/kthread.c index 76364374ff98..6051aa9d93c6 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -818,3 +818,37 @@ void flush_kthread_worker(struct kthread_worker *worker) wait_for_completion(&fwork.done); } EXPORT_SYMBOL_GPL(flush_kthread_worker); + +/** + * drain_kthread_worker - drain a kthread worker + * @worker: worker to be drained + * + * Wait until there is no work queued for the given kthread worker. + * @worker is flushed repeatedly until it becomes empty. The number + * of flushing is determined by the depth of chaining and should + * be relatively short. Whine if it takes too long. + * + * The caller is responsible for blocking all users of this kthread + * worker from queuing new works. Also it is responsible for blocking + * the already queued works from an infinite re-queuing! + */ +void drain_kthread_worker(struct kthread_worker *worker) +{ + int flush_cnt = 0; + + spin_lock_irq(&worker->lock); + + while (!list_empty(&worker->work_list)) { + spin_unlock_irq(&worker->lock); + + flush_kthread_worker(worker); + WARN_ONCE(flush_cnt++ > 10, + "kthread worker %s: drain_kthread_worker() isn't complete after %u tries\n", + worker->task->comm, flush_cnt); + + spin_lock_irq(&worker->lock); + } + + spin_unlock_irq(&worker->lock); +} +EXPORT_SYMBOL(drain_kthread_worker); -- 1.8.5.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org