From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Wed, 24 Jul 2013 13:36:10 -0700 Subject: [PATCH v2] ARM: Fix deadlock scenario with smp_send_stop() In-Reply-To: <20130724202148.GA24642@n2100.arm.linux.org.uk> Message-ID: <1374698170-26605-1-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() 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. We use local_irq_disable() here for cross-arch consistency with x86. Reported-by: Sundarajan Srinivasan Signed-off-by: Stephen Boyd --- 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); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation