Commit 4557398f authored Nov 13, 2005 by Kirill Korotaev Committed by Linus Torvalds Nov 13, 2005

[PATCH] stop_machine() vs. synchronous IPI send deadlock



This fixes deadlock of stop_machine() vs.  synchronous IPI send.  The
problem is that stop_machine() disables interrupts before disabling
preemption on other CPUs.  So if another CPU is preempted and then calls
something like flush_tlb_all() it will deadlock with CPU doing
stop_machine() and which can't process IPI due to disabled IRQs.

I changed stop_machine() to do the same things exactly as it does on other
CPUs, i.e.  it should disable preemption first on _all_ CPUs including
itself and only after that disable IRQs.

Signed-off-by: Kirill Korotaev <dev@sw.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Andrey Savochkin" <saw@sawoct.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent c5b60979

kernel/stop_machine.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -119,13 +119,12 @@ static int stop_machine(void)
		return ret;
		}

		/* Don't schedule us away at this point, please. */
		local_irq_disable();

		/* Now they are all started, make them hold the CPUs, ready. */
		preempt_disable();
		stopmachine_set_state(STOPMACHINE_PREPARE);

		/* Make them disable irqs. */
		local_irq_disable();
		stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);

		return 0;
		@@ -135,6 +134,7 @@ static void restart_machine(void)
		{
		stopmachine_set_state(STOPMACHINE_EXIT);
		local_irq_enable();
		preempt_enable_no_resched();
		}

		struct stop_machine_data