Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762405Ab3DDOz1 (ORCPT ); Thu, 4 Apr 2013 10:55:27 -0400 Received: from mail-pb0-f44.google.com ([209.85.160.44]:45610 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762388Ab3DDOzY (ORCPT ); Thu, 4 Apr 2013 10:55:24 -0400 Date: Thu, 4 Apr 2013 07:55:14 -0700 From: Tejun Heo To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, Fengguang Wu Subject: [PATCH] workqueue: avoid false negative WARN_ON() in destroy_workqueue() Message-ID: <20130404145514.GJ9425@htj.dyndns.org> References: <1365041143-3088-1-git-send-email-laijs@cn.fujitsu.com> <1365041143-3088-7-git-send-email-laijs@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1365041143-3088-7-git-send-email-laijs@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2587 Lines: 71 >From 5c529597e922c26910fe49b8d5f93aeaca9a2415 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 4 Apr 2013 10:05:38 +0800 destroy_workqueue() performs several sanity checks before proceeding with destruction of a workqueue. One of the checks verifies that refcnt of each pwq (pool_workqueue) is over 1 as at that point there should be no in-flight work items and the only holder of pwq refs is the workqueue itself. This worked fine as a workqueue used to hold only one reference to its pwqs; however, since 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues"), a workqueue may hold multiple references to its default pwq triggering this sanity check spuriously. Fix it by not triggering the pwq->refcnt assertion on default pwqs. An example spurious WARN trigger follows. WARNING: at kernel/workqueue.c:4201 destroy_workqueue+0x6a/0x13e() Hardware name: 4286C12 Modules linked in: sdhci_pci sdhci mmc_core usb_storage i915 drm_kms_helper drm i2c_algo_bit i2c_core video Pid: 361, comm: umount Not tainted 3.9.0-rc5+ #29 Call Trace: [] warn_slowpath_common+0x7c/0x93 [] warn_slowpath_null+0x22/0x24 [] destroy_workqueue+0x6a/0x13e [] ext4_put_super+0x43/0x2c4 [] generic_shutdown_super+0x4b/0xb9 [] kill_block_super+0x22/0x60 [] deactivate_locked_super+0x2f/0x56 [] deactivate_super+0x2e/0x31 [] mntput_no_expire+0x103/0x108 [] sys_umount+0x2a2/0x2c4 [] sys_oldumount+0x1e/0x20 [] sysenter_do_call+0x12/0x38 tj: Rewrote description. Signed-off-by: Lai Jiangshan Signed-off-by: Tejun Heo Reported-by: Fengguang Wu --- Applied to wq/for-3.10. Thanks. kernel/workqueue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index dd2a4c4..c273376 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4201,7 +4201,7 @@ void destroy_workqueue(struct workqueue_struct *wq) } } - if (WARN_ON(pwq->refcnt > 1) || + if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) || WARN_ON(pwq->nr_active) || WARN_ON(!list_empty(&pwq->delayed_works))) { mutex_unlock(&wq->mutex); -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/