From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>,
Rusty Russell <rusty@rustcorp.com.au>,
linux-kernel@vger.kernel.org, Li Zefan <lizf@cn.fujitsu.com>,
Miao Xie <miaox@cn.fujitsu.com>, Paul Menage <menage@google.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Gautham R Shenoy <ego@in.ibm.com>
Subject: Re: [PATCH] cpusets: fix deadlock with cpu_down()->cpuset_lock()
Date: Thu, 30 Jul 2009 09:53:42 +0800 [thread overview]
Message-ID: <4A70FD26.1010800@cn.fujitsu.com> (raw)
In-Reply-To: <20090729230043.GA28175@redhat.com>
Oleg Nesterov wrote:
> On 07/29, Oleg Nesterov wrote:
>> I strongly believe the bug does exist, but this patch needs the review
>> from maintainers.
>
> Yes...
>
>> IOW, with this patch migration_call(CPU_DEAD) runs without callback_mutex,
>> but kernel/cpuset.c always takes get_online_cpus() before callback_mutex.
>
> Oh. I'm afraid this is not an option.
>
> callback_mutex should nest under cgroup_mutex, but cpu hotplu pathes
> take cgroup_mutex under cpu_hotplug->lock. Lockdep won't be happy.
>
> Oleg.
>
We have made great effort to remove get_online_cpus() from cgroup_mutex
critical region.
We can migrate the owner of callback_mutex in migration_call(CPU_DEAD)
at first(and then take callback_mutex and migrate others).
It fixes this bug, but it can't help for your
"cpu_hotplug: don't play with current->cpus_allowed" patch.
Lai.
next prev parent reply other threads:[~2009-07-30 1:53 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-29 2:33 + cpu_hotplug-dont-affect-current-tasks-affinity.patch added to -mm tree Oleg Nesterov
2009-07-29 21:21 ` Oleg Nesterov
2009-07-29 21:22 ` [PATCH] cpusets: fix deadlock with cpu_down()->cpuset_lock() Oleg Nesterov
2009-07-29 23:00 ` Oleg Nesterov
2009-07-30 1:53 ` Lai Jiangshan [this message]
2009-07-30 17:51 ` Oleg Nesterov
2009-07-31 2:23 ` Lai Jiangshan
2009-08-01 4:42 ` [PATCH] cpusets: rework guarantee_online_cpus() to fix deadlock with cpu_down() Oleg Nesterov
2009-08-01 5:34 ` Oleg Nesterov
2009-08-02 2:18 ` Lai Jiangshan
2009-08-02 6:55 ` Oleg Nesterov
2009-08-04 7:35 ` Lai Jiangshan
2009-08-04 16:36 ` Oleg Nesterov
2009-07-29 21:42 ` [PATCH 0/1] cpu_hotplug: don't play with current->cpus_allowed Oleg Nesterov
2009-07-29 21:43 ` [PATCH 1/1] " Oleg Nesterov
2009-07-30 2:01 ` Lai Jiangshan
2009-07-30 16:32 ` Oleg Nesterov
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