From: Prarit Bhargava <prarit@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
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, Rik van Riel <riel@redhat.com>,
Mel Gorman <mgorman@suse.de>
Subject: Re: smp_call_function_single with wait=0 considered harmful
Date: Fri, 28 Feb 2014 12:34:27 -0500 [thread overview]
Message-ID: <5310C8A3.9030102@redhat.com> (raw)
In-Reply-To: <20140228123905.GK3104@twins.programming.kicks-ass.net>
On 02/28/2014 07:39 AM, Peter Zijlstra wrote:
> On Fri, Feb 28, 2014 at 01:26:24PM +0100, Peter Zijlstra wrote:
>> On Wed, Dec 04, 2013 at 08:46:27AM -0800, Christoph Hellwig wrote:
>>> kernel/stop_machine.c:stop_two_cpus()
>>
>> That site should work with .wait=1 just fine, but given the above, the
>> .wait=0 doesn't appear problematic at all.
>
> Scratch that; its broken, but not because of smp_call_function_single().
>
> ---
> 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: Prarit Bhargava <prarit@redhat.com>
P.
next prev parent reply other threads:[~2014-02-28 17:35 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-04 16:46 smp_call_function_single with wait=0 considered harmful Christoph Hellwig
2013-12-05 21:43 ` Bjorn Helgaas
2013-12-06 10:56 ` Christoph Hellwig
2014-02-28 12:26 ` Peter Zijlstra
2014-02-28 12:39 ` Peter Zijlstra
2014-02-28 17:06 ` Rik van Riel
2014-02-28 17:34 ` Prarit Bhargava [this message]
2014-03-11 12:36 ` [tip:sched/core] stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus() tip-bot for Peter Zijlstra
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