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SubjectRe: [PATCH v2] ARM: Fix deadlock scenario with smp_send_stop()
On 07/24/13 13:36, 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. We use local_irq_disable() here for cross-arch
> consistency with x86.
>
> Reported-by: Sundarajan Srinivasan <sundaraj@codeaurora.com>
> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> ---

Ok I threw this into the patch tracker because there were no more comments.

> Changes since v1:
> - Use local_irq_disable() instead of preempt_disable()
>
> arch/arm/kernel/process.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index d3ca4f6..08b47eb 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -197,6 +197,7 @@ void machine_shutdown(void)
> */
> void machine_halt(void)
> {
> + local_irq_disable();
> smp_send_stop();
>
> local_irq_disable();
> @@ -211,6 +212,7 @@ void machine_halt(void)
> */
> void machine_power_off(void)
> {
> + local_irq_disable();
> smp_send_stop();
>
> if (pm_power_off)
> @@ -230,6 +232,7 @@ void machine_power_off(void)
> */
> void machine_restart(char *cmd)
> {
> + local_irq_disable();
> smp_send_stop();
>
> arm_pm_restart(reboot_mode, cmd);


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