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

Greg Kroah-Hartman
2019-12-17T07:50:09Z

On Tue, Dec 17, 2019 at 01:38:10PM +0900, Nobuhiro Iwamatsu wrote:
> 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.

Thank you for this, now queued up everywhere.

greg k-h