Hi Paul, On Tue, Dec 12, 2017 at 09:20:59AM -0800, Paul E. McKenney wrote: > The ARM implementation of arch_cpu_idle_dead() invokes complete(), but > does so after RCU has stopped watching the outgoing CPU, which results > in lockdep complaints because complete() invokes functions containing RCU > readers. This patch therefore uses Thomas Gleixner's trick of delegating > the complete() call to a surviving CPU via smp_call_function_single(). > > Reported-by: Peng Fan <[email protected]> > Reported-by: Russell King - ARM Linux <[email protected]> > Signed-off-by: Paul E. McKenney <[email protected]> > Tested-by: Tested-by: Fabio Estevam <[email protected]>
Fabio reported only once, though he might have tested twice. baruch > Cc: Russell King <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: "Peter Zijlstra (Intel)" <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: <[email protected]> > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > index b4fbf00ee4ad..75f85e20aafa 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -267,6 +267,14 @@ void __cpu_die(unsigned int cpu) > } > > /* > + * Invoke complete() on behalf of the outgoing CPU. > + */ > +static void arch_cpu_idle_dead_complete(void *arg) > +{ > + complete(&cpu_died); > +} > + > +/* > * Called from the idle thread for the CPU which has been shutdown. > * > * Note that we disable IRQs here, but do not re-enable them > @@ -293,9 +301,11 @@ void arch_cpu_idle_dead(void) > /* > * Tell __cpu_die() that this CPU is now safe to dispose of. Once > * this returns, power and/or clocks can be removed at any point > - * from this CPU and its cache by platform_cpu_kill(). > + * from this CPU and its cache by platform_cpu_kill(). We cannot > + * call complete() this late, so we delegate it to an online CPU. > */ > - complete(&cpu_died); > + smp_call_function_single(cpumask_first(cpu_online_mask), > + arch_cpu_idle_dead_complete, NULL, 0); > > /* > * Ensure that the cache lines associated with that completion are -- http://baruch.siach.name/blog/ ~. .~ Tk Open Systems =}------------------------------------------------ooO--U--Ooo------------{= - [email protected] - tel: +972.52.368.4656, http://www.tkos.co.il -
