diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2016-03-03 04:52:10 -0500 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2016-03-03 04:52:10 -0500 |
commit | 71f87b2fc64c2e9b6d53cb817f28711b959d3dfe (patch) | |
tree | 1be0de7afced46cfca629dcbfc1807280c50bb13 | |
parent | 27d50c7eeb0f03c3d3ca72aac4d2dd487ca1f3f0 (diff) |
cpu/hotplug: Plug death reporting race
Paul noticed that the conversion of the death reporting introduced a race
where the outgoing cpu might be delayed after waking the controll processor,
so it might not be able to call rcu_report_dead() before being physically
removed, leading to RCU stalls.
We cant call complete after rcu_report_dead(), so instead of going back to
busy polling, simply issue a function call to do the completion.
Fixes: 27d50c7eeb0f "rcu: Make CPU_DYING_IDLE an explicit call"
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20160302201127.GA23440@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
-rw-r--r-- | kernel/cpu.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index ff8059b76a85..93e9d89bb0ab 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c | |||
@@ -755,14 +755,26 @@ static int notify_dead(unsigned int cpu) | |||
755 | return 0; | 755 | return 0; |
756 | } | 756 | } |
757 | 757 | ||
758 | static void cpuhp_complete_idle_dead(void *arg) | ||
759 | { | ||
760 | struct cpuhp_cpu_state *st = arg; | ||
761 | |||
762 | complete(&st->done); | ||
763 | } | ||
764 | |||
758 | void cpuhp_report_idle_dead(void) | 765 | void cpuhp_report_idle_dead(void) |
759 | { | 766 | { |
760 | struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); | 767 | struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); |
761 | 768 | ||
762 | BUG_ON(st->state != CPUHP_AP_OFFLINE); | 769 | BUG_ON(st->state != CPUHP_AP_OFFLINE); |
763 | st->state = CPUHP_AP_IDLE_DEAD; | ||
764 | complete(&st->done); | ||
765 | rcu_report_dead(smp_processor_id()); | 770 | rcu_report_dead(smp_processor_id()); |
771 | st->state = CPUHP_AP_IDLE_DEAD; | ||
772 | /* | ||
773 | * We cannot call complete after rcu_report_dead() so we delegate it | ||
774 | * to an online cpu. | ||
775 | */ | ||
776 | smp_call_function_single(cpumask_first(cpu_online_mask), | ||
777 | cpuhp_complete_idle_dead, st, 0); | ||
766 | } | 778 | } |
767 | 779 | ||
768 | #else | 780 | #else |