perf: Fix cgroup vs jump_label problem

Li Zefan reported that the jump label code sleeps and we're calling it
under a spinlock, *fail* ;-)

Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 193b190..ed253aa 100644 (file)
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -820,16 +820,8 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx)
                list_add_tail(&event->group_entry, list);
        }
 
-       if (is_cgroup_event(event)) {
+       if (is_cgroup_event(event))
                ctx->nr_cgroups++;
-               /*
-                * one more event:
-                * - that has cgroup constraint on event->cpu
-                * - that may need work on context switch
-                */
-               atomic_inc(&per_cpu(perf_cgroup_events, event->cpu));
-               jump_label_inc(&perf_sched_events);
-       }
 
        list_add_rcu(&event->event_entry, &ctx->event_list);
        if (!ctx->nr_events)
@@ -957,11 +949,8 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 
        event->attach_state &= ~PERF_ATTACH_CONTEXT;
 
-       if (is_cgroup_event(event)) {
+       if (is_cgroup_event(event))
                ctx->nr_cgroups--;
-               atomic_dec(&per_cpu(perf_cgroup_events, event->cpu));
-               jump_label_dec(&perf_sched_events);
-       }
 
        ctx->nr_events--;
        if (event->attr.inherit_stat)
@@ -2903,6 +2892,10 @@ static void free_event(struct perf_event *event)
                        atomic_dec(&nr_task_events);
                if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
                        put_callchain_buffers();
+               if (is_cgroup_event(event)) {
+                       atomic_dec(&per_cpu(perf_cgroup_events, event->cpu));
+                       jump_label_dec(&perf_sched_events);
+               }
        }
 
        if (event->buffer) {
@@ -6478,6 +6471,13 @@ SYSCALL_DEFINE5(perf_event_open,
                err = perf_cgroup_connect(pid, event, &attr, group_leader);
                if (err)
                        goto err_alloc;
+               /*
+                * one more event:
+                * - that has cgroup constraint on event->cpu
+                * - that may need work on context switch
+                */
+               atomic_inc(&per_cpu(perf_cgroup_events, event->cpu));
+               jump_label_inc(&perf_sched_events);
        }
 
        /*