perf_events: Fix broken event grouping

Events were not grouped anymore. The reason was that in
perf_event_open(), the field event->group_leader was
initialized before the function looked up the group_fd
to find the event leader. This patch fixes this by
reordering the code correctly.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Robert Richter <robert.richter@amd.com>
LKML-Reference: <20100917093009.360420946@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 86f394e15d53f54d8ea04ea7ed249d7bcc0f9ebc..ce95617f5d2c9c9b98436ff445302105c3910865 100644 (file)
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5550,17 +5550,11 @@ SYSCALL_DEFINE5(perf_event_open,
        if (event_fd < 0)
                return event_fd;
 
-       event = perf_event_alloc(&attr, cpu, group_leader, NULL, NULL);
-       if (IS_ERR(event)) {
-               err = PTR_ERR(event);
-               goto err_fd;
-       }
-
        if (group_fd != -1) {
                group_leader = perf_fget_light(group_fd, &fput_needed);
                if (IS_ERR(group_leader)) {
                        err = PTR_ERR(group_leader);
-                       goto err_alloc;
+                       goto err_fd;
                }
                group_file = group_leader->filp;
                if (flags & PERF_FLAG_FD_OUTPUT)
@@ -5569,6 +5563,12 @@ SYSCALL_DEFINE5(perf_event_open,
                        group_leader = NULL;
        }
 
+       event = perf_event_alloc(&attr, cpu, group_leader, NULL, NULL);
+       if (IS_ERR(event)) {
+               err = PTR_ERR(event);
+               goto err_fd;
+       }
+
        /*
         * Special case software events and allow them to be part of
         * any hardware group.
@@ -5653,7 +5653,6 @@ err_context:
        put_ctx(ctx);
 err_group_fd:
        fput_light(group_file, fput_needed);
-err_alloc:
        free_event(event);
 err_fd:
        put_unused_fd(event_fd);