[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>
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 84a9d18..b3d4dc8 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -119,13 +119,12 @@
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 @@
{
stopmachine_set_state(STOPMACHINE_EXIT);
local_irq_enable();
+ preempt_enable_no_resched();
}
struct stop_machine_data
