From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Wed, 5 Sep 2012 14:01:26 -0700 Subject: [PATCH] ARM: Fix deadlock scenario with smp_send_stop() Message-ID: <1346878886-7159-1-git-send-email-sboyd@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 the reboot task runs to completion. Reported-by: Sundarajan Srinivasan Signed-off-by: Stephen Boyd --- 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