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 56003c6..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;
 
@@ -7856,14 +7866,14 @@ static void perf_pmu_rotate_stop(struct pmu *pmu)
 static void __perf_event_exit_context(void *__info)
 {
        struct perf_event_context *ctx = __info;
-       struct perf_event *event, *tmp;
+       struct perf_event *event;
 
        perf_pmu_rotate_stop(ctx->pmu);
 
-       list_for_each_entry_safe(event, tmp, &ctx->pinned_groups, group_entry)
-               __perf_remove_from_context(event);
-       list_for_each_entry_safe(event, tmp, &ctx->flexible_groups, group_entry)
+       rcu_read_lock();
+       list_for_each_entry_rcu(event, &ctx->event_list, event_entry)
                __perf_remove_from_context(event);
+       rcu_read_unlock();
 }
 
 static void perf_event_exit_cpu_context(int cpu)
@@ -7887,11 +7897,12 @@ static void perf_event_exit_cpu(int cpu)
 {
        struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
 
+       perf_event_exit_cpu_context(cpu);
+
        mutex_lock(&swhash->hlist_mutex);
+       swhash->online = false;
        swevent_hlist_release(swhash);
        mutex_unlock(&swhash->hlist_mutex);
-
-       perf_event_exit_cpu_context(cpu);
 }
 #else
 static inline void perf_event_exit_cpu(int cpu) { }