perf/core: Fix lock inversion between perf,trace,cpuhp

[sfrench/cifs-2.6.git] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4df5b695bf0db1c035a22b914d87ad190d1a0f42..2d80824298a71902b2ef06ec3659ab7513444797 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1231,6 +1231,10 @@ static void put_ctx(struct perf_event_context *ctx)
  *           perf_event_context::lock
  *         perf_event::mmap_mutex
  *         mmap_sem
+ *
+ *    cpu_hotplug_lock
+ *      pmus_lock
+ *       cpuctx->mutex / perf_event_context::mutex
  */
 static struct perf_event_context *
 perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
@@ -4196,6 +4200,7 @@ int perf_event_release_kernel(struct perf_event *event)
 {
        struct perf_event_context *ctx = event->ctx;
        struct perf_event *child, *tmp;
+       LIST_HEAD(free_list);
 
        /*
         * If we got here through err_file: fput(event_file); we will not have
@@ -4268,8 +4273,7 @@ again:
                                               struct perf_event, child_list);
                if (tmp == child) {
                        perf_remove_from_context(child, DETACH_GROUP);
-                       list_del(&child->child_list);
-                       free_event(child);
+                       list_move(&child->child_list, &free_list);
                        /*
                         * This matches the refcount bump in inherit_event();
                         * this can't be the last reference.
@@ -4284,6 +4288,11 @@ again:
        }
        mutex_unlock(&event->child_mutex);
 
+       list_for_each_entry_safe(child, tmp, &free_list, child_list) {
+               list_del(&child->child_list);
+               free_event(child);
+       }
+
 no_ctx:
        put_event(event); /* Must be the 'last' reference */
        return 0;