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-rw-r--r--kernel/smp.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index 4ec30e069987..17c6e5860231 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);