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Date: Sat, 5 Jul 2014 19:10:15 +0100 From: Russell King - ARM Linux <linux@....linux.org.uk> To: pawandeep oza <oza.contri.linux.kernel@...il.com> Cc: akpm@...ux-foundation.org, holt@....com, mingo@...nel.org, sboyd@...eaurora.org, k.khlebnikov@...sung.com, u.kleine-koenig@...gutronix.de, nicolas.pitre@...aro.org, linux-arm-kernel@...ts.infradead.or, linux-kernel@...r.kernel.org Subject: Re: [PATCH] machine_power_off: not only local_irq_disable but also do disable preemption On Sat, Jul 05, 2014 at 10:44:41PM +0530, pawandeep oza wrote: > 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 Please explain how that <PREEMPT> occurs with IRQs already disabled. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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