From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, Lai Jiangshan <laijs@cn.fujitsu.com>,
Tejun Heo <tj@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: Q: select_fallback_rq() && cpuset_lock()
Date: Thu, 11 Mar 2010 16:22:01 +0100 [thread overview]
Message-ID: <20100311152201.GA13888@redhat.com> (raw)
In-Reply-To: <20100311145248.GA12907@redhat.com>
On 03/11, Oleg Nesterov wrote:
>
> How can we fix this later? Perhaps we can change
> cpuset_track_online_cpus(CPU_DEAD) to scan all affected cpusets and
> fixup the tasks with the wrong ->cpus_allowed == cpu_possible_mask.
Wait. We need to fix the CPU_DEAD case anyway?
Hmm. 6ad4c18884e864cf4c77f9074d3d1816063f99cd
"sched: Fix balance vs hotplug race" did s/CPU_DEAD/CPU_DOWN_PREPARE/
in cpuset_track_online_cpus(). This doesn't look exactly right to me,
we shouldn't do remove_tasks_in_empty_cpuset() at CPU_DOWN_PREPARE
stage, it can fail.
Otoh. This means that move_task_of_dead_cpu() can never see the
task without active cpus in ->cpus_allowed, it is called later by
CPU_DEAD. So, cpuset_lock() is not needed at all.
Oleg.
next prev parent reply other threads:[~2010-03-11 15:23 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-09 18:06 Q: select_fallback_rq() && cpuset_lock() Oleg Nesterov
2010-03-10 16:40 ` Peter Zijlstra
2010-03-10 17:30 ` Oleg Nesterov
2010-03-10 18:01 ` Peter Zijlstra
2010-03-10 18:33 ` Oleg Nesterov
2010-03-11 14:52 ` Oleg Nesterov
2010-03-11 15:22 ` Oleg Nesterov [this message]
2010-03-11 15:41 ` Peter Zijlstra
2010-03-11 15:35 ` Peter Zijlstra
2010-03-11 16:19 ` Oleg Nesterov
2010-03-11 16:29 ` Peter Zijlstra
2010-03-13 19:28 ` Oleg Nesterov
2010-03-14 2:11 ` Peter Zijlstra
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