Revert "perf: Fix exit() vs PERF_FORMAT_GROUP"

This reverts commit 4fd38e45.

It causes various crashes and hangs when events are activated.

The cause is not fully understood yet but we need to revert it
because the effects are severe.
Reported-by: NStephane Eranian <eranian@google.com>
Reported-by: NLin Ming <ming.m.lin@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/linux/perf_event.h

@@ -575,7 +575,6 @@ struct pmu {
  * enum perf_event_active_state - the states of a event
  */
 enum perf_event_active_state {
-	PERF_EVENT_STATE_FREE		= -3,
 	PERF_EVENT_STATE_ERROR		= -2,
 	PERF_EVENT_STATE_OFF		= -1,
 	PERF_EVENT_STATE_INACTIVE	=  0,

kernel/perf_event.c

@@ -334,9 +334,6 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 	if (event->state > PERF_EVENT_STATE_OFF)
 		event->state = PERF_EVENT_STATE_OFF;
 
-	if (event->state > PERF_EVENT_STATE_FREE)
-		return;
-
 	/*
 	 * If this was a group event with sibling events then
 	 * upgrade the siblings to singleton events by adding them
@@ -1871,8 +1868,6 @@ int perf_event_release_kernel(struct perf_event *event)
 {
 	struct perf_event_context *ctx = event->ctx;
 
-	event->state = PERF_EVENT_STATE_FREE;
-
 	WARN_ON_ONCE(ctx->parent_ctx);
 	/*
 	 * There are two ways this annotation is useful: