linux-kernel - Re: smp_call_function_single with wait=0 considered harmful

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Message-ID: <5310C231.5000503@redhat.com>
Date:	Fri, 28 Feb 2014 12:06:57 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Christoph Hellwig <hch@...radead.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	Robert Richter <rric@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	David Daney <david.daney@...ium.com>,
	linux-kernel@...r.kernel.org, Prarit Bhargava <prarit@...hat.com>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: smp_call_function_single with wait=0 considered harmful

On 02/28/2014 07:39 AM, Peter Zijlstra wrote:

> Subject: stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus()
> 
> We must use smp_call_function_single(.wait=1) for the
> irq_cpu_stop_queue_work() to ensure the queueing is actually done under
> stop_cpus_lock. Without this we could have dropped the lock by the time
> we do the queueing and get the race we tried to fix.
> 
> Fixes: 7053ea1a34fa ("stop_machine: Fix race between stop_two_cpus() and stop_cpus()")
> Cc: Prarit Bhargava <prarit@...hat.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>

Reviewed-by: Rik van Riel <riel@...hat.com>

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