[tip:perf/core] perf: Fix errors path in perf_output_begin()

[tip-bot for Stephane Eranian <eranian@google.com>]

Commit-ID:  00d1d0b095ba4e5c0958cb228b2a9c445d4a339d
Gitweb:     http://git.kernel.org/tip/00d1d0b095ba4e5c0958cb228b2a9c445d4a339d
Author:     Stephane Eranian <eranian@google.com>
AuthorDate: Mon, 17 May 2010 12:46:01 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 18 May 2010 18:35:47 +0200

perf: Fix errors path in perf_output_begin()

In case the sampling buffer has no "payload" pages,
nr_pages is 0. The problem is that the error path in
perf_output_begin() skips to a label which assumes
perf_output_lock() has been issued which is not the
case. That triggers a WARN_ON() in
perf_output_unlock().

This patch fixes the problem by skipping
perf_output_unlock() in case data->nr_pages is 0.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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: <4bf13674.014fd80a.6c82.ffffb20c@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/perf_event.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 17ac47f..8d61d29 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3036,7 +3036,7 @@ int perf_output_begin(struct perf_output_handle *handle,
 	handle->sample	= sample;
 
 	if (!data->nr_pages)
-		goto fail;
+		goto out;
 
 	have_lost = atomic_read(&data->lost);
 	if (have_lost)