Re: [PATCH 4.19 053/140] workqueue: Fix spurious sanity check failures in destroy_workqueue()

Nobuhiro Iwamatsu
2019-12-17T04:38:29Z

On Mon, Dec 16, 2019 at 06:48:41PM +0100, Greg Kroah-Hartman wrote:
> From: Tejun Heo <tj@kernel.org>
>
> commit def98c84b6cdf2eeea19ec5736e90e316df5206b upstream.
>
> Before actually destrying a workqueue, destroy_workqueue() checks
> whether it's actually idle. If it isn't, it prints out a bunch of
> warning messages and leaves the workqueue dangling. It unfortunately
> has a couple issues.
>
> * Mayday list queueing increments pwq's refcnts which gets detected as
> busy and fails the sanity checks. However, because mayday list
> queueing is asynchronous, this condition can happen without any
> actual work items left in the workqueue.
>
> * Sanity check failure leaves the sysfs interface behind too which can
> lead to init failure of newer instances of the workqueue.
>
> This patch fixes the above two by
>
> * If a workqueue has a rescuer, disable and kill the rescuer before
> sanity checks. Disabling and killing is guaranteed to flush the
> existing mayday list.
>
> * Remove sysfs interface before sanity checks.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reported-by: Marcin Pawlowski <mpawlowski@fb.com>
> Reported-by: "Williams, Gerald S" <gerald.s.williams@intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>

This commit also requires the following commit:

commit 8efe1223d73c218ce7e8b2e0e9aadb974b582d7f
Author: Tejun Heo <tj@kernel.org>
Date: Fri Sep 20 13:39:57 2019 -0700

workqueue: Fix missing kfree(rescuer) in destroy_workqueue()

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Qian Cai <cai@lca.pw>
Fixes: def98c84b6cd ("workqueue: Fix spurious sanity check failures in destroy_workqueue()")

This is also required to 4.4, 4.9, 4.14 and 5.3.

Best regards,
Nobuhiro