| Message ID | 1346878886-7159-1-git-send-email-sboyd@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/05/12 14:01, 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 the reboot task runs to > completion. > > Reported-by: Sundarajan Srinivasan <sundaraj@codeaurora.com> > Signed-off-by: Stephen Boyd <sboyd@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(). Any comments? > > 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
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
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 <sundaraj@codeaurora.com> Signed-off-by: Stephen Boyd <sboyd@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(+)