| Message ID | 1374698170-26605-1-git-send-email-sboyd@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/24/13 13:36, Stephen Boyd wrote: > 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> > --- Ok I threw this into the patch tracker because there were no more comments. > 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);
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);
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(+)