linux-kernel - Re: workqueue: race in mod_delayed_work

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Message-ID: <20160510163625.GM7110@mtj.duckdns.org>
Date:	Tue, 10 May 2016 12:36:25 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: workqueue: race in mod_delayed_work_on?

Hello,

On Tue, May 10, 2016 at 07:28:08PM +0300, Konstantin Khlebnikov wrote:
> On 10.05.2016 11:21, Konstantin Khlebnikov wrote:
> >I've got plenty warnings, bugs and oops around trivial use of mod_delayed_work in drivers/infiniband/core/addr.c
> 
> Looks like problem in mod_delayed_work_on was hidden because add_timer is equal to mod_timer

The timer usages are gated behind PENDING bit, so whether add_timer()
is equal to mod_timer() shouldn't matter.

> but Sasha accidentally backported 874bbfe600a660cba9c776b3957b1ce393151b76
> (workqueue: make sure delayed work run in local cpu) into 3.18.25
> 
> I don't see reason why that commit could break delayed work,
> most likely it highlighted some other problem.

What are you running?  Can you reproduce the issue on upstream kernel?

-- 
tejun