---

yaml
---
r: 232024
b: refs/heads/master
c: 6dc1989
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 713735b4233fad3ae35b5cad656baa41413887ca
+refs/heads/master: 6dc19899958e420a931274b94019e267e2396d3e

trunk/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);