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Subject[PATCH v2] ARM: Fix deadlock scenario with smp_send_stop()
Date
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>
---

Changes since v1:
- Use local_irq_disable() instead of preempt_disable()

arch/arm/kernel/process.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index d3ca4f6..08b47eb 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -197,6 +197,7 @@ void machine_shutdown(void)
*/
void machine_halt(void)
{
+ local_irq_disable();
smp_send_stop();

local_irq_disable();
@@ -211,6 +212,7 @@ void machine_halt(void)
*/
void machine_power_off(void)
{
+ local_irq_disable();
smp_send_stop();

if (pm_power_off)
@@ -230,6 +232,7 @@ void machine_power_off(void)
*/
void machine_restart(char *cmd)
{
+ local_irq_disable();
smp_send_stop();

arm_pm_restart(reboot_mode, cmd);
--
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