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| author | Thomas Gleixner <tglx@linutronix.de> | 2016-03-03 10:52:10 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-03-03 10:52:10 +0100 |
| commit | 71f87b2fc64c2e9b6d53cb817f28711b959d3dfe (patch) | |
| tree | 1be0de7afced46cfca629dcbfc1807280c50bb13 | |
| parent | 27d50c7eeb0f03c3d3ca72aac4d2dd487ca1f3f0 (diff) | |
| download | linux-71f87b2fc64c2e9b6d53cb817f28711b959d3dfe.tar.bz2 | |
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) return 0; } +static void cpuhp_complete_idle_dead(void *arg) +{ + struct cpuhp_cpu_state *st = arg; + + complete(&st->done); +} + void cpuhp_report_idle_dead(void) { struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); BUG_ON(st->state != CPUHP_AP_OFFLINE); - st->state = CPUHP_AP_IDLE_DEAD; - complete(&st->done); rcu_report_dead(smp_processor_id()); + st->state = CPUHP_AP_IDLE_DEAD; + /* + * We cannot call complete after rcu_report_dead() so we delegate it + * to an online cpu. + */ + smp_call_function_single(cpumask_first(cpu_online_mask), + cpuhp_complete_idle_dead, st, 0); } #else |