diff options
| -rw-r--r-- | kernel/smp.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/kernel/smp.c b/kernel/smp.c index 9910744f0856..aaeee20c5634 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -491,14 +491,15 @@ void smp_call_function_many(const struct cpumask *mask, cpumask_clear_cpu(this_cpu, data->cpumask); /* - * To ensure the interrupt handler gets an complete view - * we order the cpumask and refs writes and order the read - * of them in the interrupt handler. In addition we may - * only clear our own cpu bit from the mask. + * We reuse the call function data without waiting for any grace + * period after some other cpu removes it from the global queue. + * This means a cpu might find our data block as it is writen. + * The interrupt handler waits until it sees refs filled out + * while its cpu mask bit is set; here we may only clear our + * own cpu mask bit, and must wait to set refs until we are sure + * previous writes are complete and we have obtained the lock to + * add the element to the queue. */ - smp_wmb(); - - atomic_set(&data->refs, cpumask_weight(data->cpumask)); raw_spin_lock_irqsave(&call_function.lock, flags); /* @@ -507,6 +508,11 @@ void smp_call_function_many(const struct cpumask *mask, * will not miss any other list entries: */ list_add_rcu(&data->csd.list, &call_function.queue); + /* + * We rely on the wmb() in list_add_rcu to order the writes + * to func, data, and cpumask before this write to refs. + */ + atomic_set(&data->refs, cpumask_weight(data->cpumask)); raw_spin_unlock_irqrestore(&call_function.lock, flags); /* |