[ Upstream commit 6add129c5d9210ada25217abc130df0b7096ee02 ]

When fail to mmap events in task exit case, it misses to set 'err' to
-1; thus the testing will not report failure for it.

This patch sets 'err' to -1 when fails to mmap events, thus Perf tool
can report correct result.

Fixes: d723a550 ("perf test: Add test case for checking number of EXIT events")
Signed-off-by: NLeo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20191011091942.29841-1-leo.yan@linaro.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>