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);