Commit 240eea98 authored May 07, 2014 by Arun KS Committed by Trilok Soni Jun 08, 2014

arm64: Fix deadlock scenario with smp_send_stop()



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);
 <PREEMPT>
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.

Change-Id: I7c2810dadccfff47addbb62129f72e026118f18f
Based-on-work-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Arun KS <getarunks@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: b9acc49ee9464f8f8232a790045d057eb158e869
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Trilok Soni <tsoni@codeaurora.org>

parent beb97697

arch/arm64/kernel/process.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -128,6 +128,7 @@ void machine_shutdown(void)
		*/
		void machine_halt(void)
		{
		local_irq_disable();
		smp_send_stop();
		while (1);
		}
		@@ -140,6 +141,7 @@ void machine_halt(void)
		*/
		void machine_power_off(void)
		{
		local_irq_disable();
		smp_send_stop();
		if (pm_power_off)
		pm_power_off();
		@@ -158,10 +160,9 @@ 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)