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Date: Fri, 28 Feb 2014 12:06:57 -0500
From: Rik van Riel <riel@redhat.com>
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To: Peter Zijlstra <peterz@infradead.org>,
        Christoph Hellwig <hch@infradead.org>
CC: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Tony Luck <tony.luck@intel.com>,
        Robert Richter <rric@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        David Daney <david.daney@cavium.com>, linux-kernel@vger.kernel.org,
        Prarit Bhargava <prarit@redhat.com>, Mel Gorman <mgorman@suse.de>
Subject: Re: smp_call_function_single with wait=0 considered harmful
References: <20131204164627.GA27677@infradead.org> <20140228122624.GF9987@twins.programming.kicks-ass.net> <20140228123905.GK3104@twins.programming.kicks-ass.net>
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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@redhat.com>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>

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

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