Re: [PATCH] ARM: Fix deadlock scenario with smp_send_stop()

From: Stephen Boyd
Date: Wed Jul 24 2013 - 16:29:07 EST

On 07/24/13 13:21, Russell King - ARM Linux wrote:
> On Wed, Jul 24, 2013 at 11:56:18AM -0700, Stephen Boyd wrote:
>> On 07/09, Stephen Boyd wrote:
>>> If one process calls sys_reboot and that process then stops other
>>> CPUs while those CPUs are within a spin_lock() region we can
>>> potentially encounter a deadlock scenario like below.
>>> CPU 0 CPU 1
>>> ----- -----
>>> spin_lock(my_lock)
>>> smp_send_stop()
>>> <send IPI> handle_IPI()
>>> disable_preemption/irqs
>>> while(1);
>>> spin_lock(my_lock) <--- Waits forever
>>> We shouldn't attempt to run any other tasks after we send a stop
>>> IPI to a CPU so disable preemption so that this task runs to
>>> completion.
>>> Reported-by: Sundarajan Srinivasan <sundaraj@xxxxxxxxxxxxxx>
>>> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
>>> ---
>>> Resending this patch now that the context has changed.
>> Ping? Shall I put this in the patch tracker?
> Well, looking at x86, they use local_irq_disable() before sending the
> stop, so I think we should do the same for cross-arch consistency.

Fair enough. I'll send v2 with that.

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