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.
Reported-by: Sundarajan Srinivasan <sundaraj@codeaurora.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
44424c3404