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>

1 files changed, 7 insertions, 8 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 86f394e15d53..ce95617f5d2c 100644
--- 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);