perf: Prevent false warning in perf_swevent_add

[platform/adaptation/renesas_rcar/renesas_kernel.git] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index fa0b2d4..e80611f 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5406,6 +5406,9 @@ 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);
@@ -5652,8 +5655,14 @@ 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);
 
@@ -7833,6 +7842,7 @@ 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;
 
@@ -7890,6 +7900,7 @@ 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);
 }