Messages in this thread Patch in this message | | | From | Stephen Boyd <> | Subject | [PATCH] ARM: Fix deadlock scenario with smp_send_stop() | Date | Wed, 5 Sep 2012 14:01:26 -0700 |
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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 the reboot task runs to completion.
Reported-by: Sundarajan Srinivasan <sundaraj@codeaurora.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> ---
Unfortunately this won't fix the other problem I mentioned two weeks ago where smp_send_stop races with other CPUs calling cpu_up().
arch/arm/kernel/process.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 693b744..663a7a8 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -239,6 +239,7 @@ __setup("reboot=", reboot_setup); void machine_shutdown(void) { + preempt_disable(); #ifdef CONFIG_SMP smp_send_stop(); #endif -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation
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