From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Wed, 24 Jul 2013 13:29:00 -0700 Subject: [PATCH] ARM: Fix deadlock scenario with smp_send_stop() In-Reply-To: <20130724202148.GA24642@n2100.arm.linux.org.uk> References: <1373384217-26307-1-git-send-email-sboyd@codeaurora.org> <20130724185618.GD27761@codeaurora.org> <20130724202148.GA24642@n2100.arm.linux.org.uk> Message-ID: <51F0390C.7090501@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 07/24/13 13:21, Russell King - ARM Linux wrote: > On Wed, Jul 24, 2013 at 11:56:18AM -0700, Stephen Boyd wrote: >> On 07/09, 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() >>> 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. >>> >>> Reported-by: Sundarajan Srinivasan >>> Signed-off-by: Stephen Boyd >>> --- >>> >>> Resending this patch now that the context has changed. >> Ping? Shall I put this in the patch tracker? > Well, looking at x86, they use local_irq_disable() before sending the > stop, so I think we should do the same for cross-arch consistency. Fair enough. I'll send v2 with that. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation