Re: [PATCH] ARM: Fix deadlock scenario with smp_send_stop()
From: Russell King - ARM Linux
Date: Wed Jul 24 2013 - 16:22:05 EST
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);
> > <PREEMPT>
> > 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.
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