Hello Andrew,
This patch 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 <[email protected]>
Kirill
--- ./kernel/stop_machine.c.stpmach 2005-11-01 12:06:03.000000000 +0300
+++ ./kernel/stop_machine.c 2005-11-09 13:58:03.000000000 +0300
@@ -114,13 +114,12 @@ 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;
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