From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753398AbaBOPOp (ORCPT ); Sat, 15 Feb 2014 10:14:45 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:12609 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753358AbaBOPOn (ORCPT ); Sat, 15 Feb 2014 10:14:43 -0500 X-IronPort-AV: E=Sophos;i="4.95,850,1384272000"; d="scan'208";a="9531914" From: Lai Jiangshan To: linux-kernel@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , stable@vger.kernel.org Subject: [PATCH] workqueue: ensure @task is valid across kthread_stop() Date: Sat, 15 Feb 2014 22:02:28 +0800 Message-Id: <1392472948-2486-1-git-send-email-laijs@cn.fujitsu.com> X-Mailer: git-send-email 1.7.7.6 X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/15 22:00:34, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/15 22:00:36, Serialize complete at 2014/02/15 22:00:36 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a worker is set WORKER_DIE, it may die very quickly, and kthread_stop() will access to a stale task stuct/stack. To avoid this, we use get_task_struct() to ensure @task is valid. See more comments in kthread_create_on_node()&kthread_stop(). Note: comments in kthread_create_on_node() does not elaborate any use case like this patch, but it is a valid way to use kthread_stop(). CC: stable@vger.kernel.org Signed-off-by: Lai Jiangshan --- kernel/workqueue.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 82ef9f3..783d5f2 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1856,9 +1856,12 @@ static void destroy_worker(struct worker *worker) idr_remove(&pool->worker_idr, worker->id); + /* Enusre the @worker->task is valid across kthread_stop() */ + get_task_struct(worker->task); spin_unlock_irq(&pool->lock); kthread_stop(worker->task); + put_task_struct(worker->task); kfree(worker); spin_lock_irq(&pool->lock); -- 1.7.7.6