perf_counter: Log vfork as a fork event

Right now we don't output vfork events. Even though we should
always see an exec after a vfork, we may get perfcounter
samples between the vfork and exec. These samples can lead to
some confusion when parsing perfcounter data.

To keep things consistent we should always log a fork event. It
will result in a little more log data, but is less confusing to
trace parsing tools.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090716104817.589309391@samba.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/fork.c

@@ -1408,14 +1408,11 @@ long do_fork(unsigned long clone_flags,
 		if (clone_flags & CLONE_VFORK) {
 			p->vfork_done = &vfork;
 			init_completion(&vfork);
-		} else if (!(clone_flags & CLONE_VM)) {
-			/*
-			 * vfork will do an exec which will call
-			 * set_task_comm()
-			 */
-			perf_counter_fork(p);
 		}
 
+		if (!(clone_flags & CLONE_THREAD))
+			perf_counter_fork(p);
+
 		audit_finish_fork(p);
 		tracehook_report_clone(regs, clone_flags, nr, p);