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From: Steven Rostedt <rostedt@goodmis.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Tejun Heo <htejun@gmail.com>, Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	tglx@linutronix.de, "Steven J . Hill" <steven.hill@cavium.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH] Revert mm/vmstat.c: fix vmstat_update() preemption BUG
Date: Wed, 27 Jun 2018 08:36:57 -0400	[thread overview]
Message-ID: <20180627123657.2hb7ow4szjyhg5aj@home.goodmis.org> (raw)
In-Reply-To: <20180411190729.7sbmbsxtkcng7ddx@linutronix.de>

On Wed, Apr 11, 2018 at 09:07:30PM +0200, Sebastian Andrzej Siewior wrote:
> 
> This already happens:
> - vmstat_shepherd() does get_online_cpus() and within this block it does
>   queue_delayed_work_on(). So this has to wait until cpuhotplug
>   completed before it can schedule something and then it won't schedule
>   anything on the "off" CPU.

But can't we have something like this happen: ?

	CPU0			CPU1			CPU2
	----			----			----
 get_online_cpus()
 queue_work(vmstat_update, cpu1)
    wakeup(kworker/1)
			     High prio task running
 put_online_cpus()
 						     Shutdown CPU 1
			     migrate kworker/1
 schedule kworker/1
 (smp_processor_id() != 1)

-- Steve


  parent reply	other threads:[~2018-06-27 12:37 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-11  9:57 [PATCH] Revert mm/vmstat.c: fix vmstat_update() preemption BUG Sebastian Andrzej Siewior
2018-04-11 13:56 ` Vlastimil Babka
2018-04-11 14:09   ` Tejun Heo
2018-04-11 14:42     ` Sebastian Andrzej Siewior
2018-04-11 19:07       ` Sebastian Andrzej Siewior
2018-04-18 15:44         ` Sebastian Andrzej Siewior
2018-04-18 19:54           ` Andrew Morton
2018-06-27 12:36         ` Steven Rostedt [this message]
2018-06-27 12:47           ` Sebastian Andrzej Siewior

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