diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/smp.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/smp.c b/kernel/smp.c index 4ec30e06998..17c6e586023 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -195,6 +195,24 @@ void generic_smp_call_function_interrupt(void) list_for_each_entry_rcu(data, &call_function.queue, csd.list) { int refs; + /* + * Since we walk the list without any locks, we might + * see an entry that was completed, removed from the + * list and is in the process of being reused. + * + * We must check that the cpu is in the cpumask before + * checking the refs, and both must be set before + * executing the callback on this cpu. + */ + + if (!cpumask_test_cpu(cpu, data->cpumask)) + continue; + + smp_rmb(); + + if (atomic_read(&data->refs) == 0) + continue; + if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) continue; @@ -203,6 +221,8 @@ void generic_smp_call_function_interrupt(void) refs = atomic_dec_return(&data->refs); WARN_ON(refs < 0); if (!refs) { + WARN_ON(!cpumask_empty(data->cpumask)); + raw_spin_lock(&call_function.lock); list_del_rcu(&data->csd.list); raw_spin_unlock(&call_function.lock); @@ -454,11 +474,21 @@ void smp_call_function_many(const struct cpumask *mask, data = &__get_cpu_var(cfd_data); csd_lock(&data->csd); + BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask)); data->csd.func = func; data->csd.info = info; cpumask_and(data->cpumask, mask, cpu_online_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. + */ + smp_wmb(); + atomic_set(&data->refs, cpumask_weight(data->cpumask)); raw_spin_lock_irqsave(&call_function.lock, flags); |