From mboxrd@z Thu Jan 1 00:00:00 1970 From: arunks.linux@gmail.com (arunks.linux at gmail.com) Date: Wed, 7 May 2014 07:11:23 +0530 Subject: [PATCH v1 2/2] arm64: Fix deadlock scenario with smp_send_stop() In-Reply-To: <1399426883-13779-1-git-send-email-arunks.linux@gmail.com> References: <1399426883-13779-1-git-send-email-arunks.linux@gmail.com> Message-ID: <1399426883-13779-2-git-send-email-arunks.linux@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Arun KS 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. Based-on-work-by: Stephen Boyd Signed-off-by: Arun KS --- arch/arm64/kernel/process.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 2d43614..abe57e0 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -134,6 +134,7 @@ void machine_shutdown(void) */ void machine_halt(void) { + local_irq_disable(); smp_send_stop(); while (1); } @@ -146,6 +147,7 @@ void machine_halt(void) */ void machine_power_off(void) { + local_irq_disable(); smp_send_stop(); if (pm_power_off) pm_power_off(); @@ -164,10 +166,9 @@ void machine_power_off(void) */ void machine_restart(char *cmd) { - smp_send_stop(); - /* Disable interrupts first */ local_irq_disable(); + smp_send_stop(); /* Now call the architecture specific reboot code. */ if (arm_pm_restart) -- 1.7.6