1 files changed, 12 insertions, 1 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1d1ec6453a08..feb1329ca331 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5419,6 +5419,9 @@ struct swevent_htable {
 
         /* Recursion avoidance in each contexts */
         int                             recursion[PERF_NR_CONTEXTS];
+
+        /* Keeps track of cpu being initialized/exited */
+        bool                            online;
 };
 
 static DEFINE_PER_CPU(struct swevent_htable, swevent_htable);
@@ -5665,8 +5668,14 @@ static int perf_swevent_add(struct perf_event *event, int flags)
         hwc->state = !(flags & PERF_EF_START);
 
         head = find_swevent_head(swhash, event);
-        if (WARN_ON_ONCE(!head))
+        if (!head) {
+                /*
+                 * We can race with cpu hotplug code. Do not
+                 * WARN if the cpu just got unplugged.
+                 */
+                WARN_ON_ONCE(swhash->online);
                 return -EINVAL;
+        }
 
         hlist_add_head_rcu(&event->hlist_entry, head);
 
@@ -7845,6 +7854,7 @@ static void perf_event_init_cpu(int cpu)
         struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
 
         mutex_lock(&swhash->hlist_mutex);
+        swhash->online = true;
         if (swhash->hlist_refcount > 0) {
                 struct swevent_hlist *hlist;
 
@@ -7902,6 +7912,7 @@ static void perf_event_exit_cpu(int cpu)
         perf_event_exit_cpu_context(cpu);
 
         mutex_lock(&swhash->hlist_mutex);
+        swhash->online = false;
         swevent_hlist_release(swhash);
         mutex_unlock(&swhash->hlist_mutex);
 }