From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>,
jjherne@linux.vnet.ibm.com, Sasha Levin <sasha.levin@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
Dave Jones <davej@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: workqueue: WARN at at kernel/workqueue.c:2176
Date: Fri, 16 May 2014 08:08:22 -0400 [thread overview]
Message-ID: <20140516120822.GA13288@mtj.dyndns.org> (raw)
In-Reply-To: <20140516115737.GP11096@twins.programming.kicks-ass.net>
Hello, Peter.
On Fri, May 16, 2014 at 01:57:37PM +0200, Peter Zijlstra wrote:
> This of course leaves the question how the workqueue code manages to
> call set_cpu_allowed_ptr() on a cpu _before_ its online.
>
> That too sounds fishy.. with the proposed patch the
> set_cpus_allowed_ptr() will 'gracefully' fail, but calling it in the
> first place is of course dubious too.
Right after being created, a workqueue worker invokes
set_cpus_allowed_ptr() to the target cpumask without checking whether
the cpu[s] are online or not and it's allowed to fail. The guarantee
there is that the worker is already registered by that point and if a
CPU comes online after the registration, CPU_ONLINE notification will
update the cpumask accordingly, so either way the worker is guaranteed
to be on the right cpumask.
Thanks.
--
tejun
next prev parent reply other threads:[~2014-05-16 12:08 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-12 18:58 Sasha Levin
2014-05-12 20:01 ` Tejun Heo
2014-05-13 2:19 ` Lai Jiangshan
2014-05-13 2:17 ` Sasha Levin
2014-05-14 16:52 ` Jason J. Herne
2014-05-16 3:50 ` Lai Jiangshan
2014-05-16 9:35 ` Peter Zijlstra
2014-05-16 9:56 ` Lai Jiangshan
2014-05-16 10:29 ` Peter Zijlstra
2014-05-16 10:15 ` Peter Zijlstra
2014-05-16 10:16 ` Peter Zijlstra
2014-05-16 10:39 ` Peter Zijlstra
2014-05-16 11:57 ` Peter Zijlstra
2014-05-16 12:08 ` Tejun Heo [this message]
2014-05-16 12:14 ` Thomas Gleixner
2014-05-16 12:16 ` Tejun Heo
2014-05-16 16:18 ` Lai Jiangshan
2014-05-16 16:29 ` Peter Zijlstra
2014-05-27 14:18 ` Jason J. Herne
2014-05-27 14:26 ` Peter Zijlstra
2014-05-29 16:23 ` Jason J. Herne
2014-06-03 11:24 ` Lai Jiangshan
2014-06-03 12:45 ` Lai Jiangshan
2014-06-03 14:28 ` Peter Zijlstra
2014-06-04 1:47 ` Lai Jiangshan
2014-06-03 14:16 ` Peter Zijlstra
2014-06-04 2:27 ` Lai Jiangshan
2014-06-04 6:49 ` Peter Zijlstra
2014-06-04 8:25 ` Lai Jiangshan
2014-06-04 9:39 ` Peter Zijlstra
2014-06-05 10:54 ` Lai Jiangshan
2014-06-05 15:22 ` Jason J. Herne
2014-06-06 12:39 ` Jason J. Herne
2014-06-06 13:36 ` Peter Zijlstra
2014-06-08 2:50 ` Lai Jiangshan
2014-09-01 3:04 ` Lai Jiangshan
2014-09-03 15:15 ` Peter Zijlstra
2014-09-04 2:22 ` Lai Jiangshan
2014-09-04 6:39 ` Peter Zijlstra
2014-06-09 14:01 ` Jason J. Herne
2014-06-10 1:21 ` Lai Jiangshan
2014-06-16 1:30 ` Lai Jiangshan
2014-09-09 14:52 ` [tip:sched/core] sched: Migrate waking tasks tip-bot for Lai Jiangshan
2014-09-10 7:38 ` Kirill Tkhai
2014-09-10 7:53 ` Peter Zijlstra
2014-06-04 2:28 ` workqueue: WARN at at kernel/workqueue.c:2176 Lai Jiangshan
2014-06-04 6:48 ` Peter Zijlstra
2014-05-19 13:07 ` [tip:sched/core] sched: Fix hotplug vs set_cpus_allowed_ptr() tip-bot for Lai Jiangshan
2014-05-22 12:26 ` [tip:sched/core] sched: Fix hotplug vs. set_cpus_allowed_ptr() tip-bot for Lai Jiangshan
2014-05-22 22:02 ` Srivatsa S. Bhat
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