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 the reboot task runs to
completion.
Reported-by: Sundarajan Srinivasan <sunda...@codeaurora.com>
Signed-off-by: Stephen Boyd <sb...@codeaurora.org>
---
Unfortunately this won't fix the other problem I mentioned two weeks
ago where smp_send_stop races with other CPUs calling cpu_up().
arch/arm/kernel/process.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 693b744..663a7a8 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -239,6 +239,7 @@ __setup("reboot=", reboot_setup);
void machine_shutdown(void)
{
+ preempt_disable();
#ifdef CONFIG_SMP
smp_send_stop();
#endif
--
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