[PATCH V2] perf test: Fix test perf stat tests for virtualized machines

[Thomas Richter <tmricht@linux.ibm.com>]

V1 --> V2: Add correct Fixes: tag, suggested by James Clark

On s390 perf test 'perf stat tests', subtest test_hybrid fails
for z/VM systems.
The root cause is this statement:

  $(perf stat -a -- sleep 0.1 2>&1 |\
                  grep -E "/cpu-cycles/[uH]*|  cpu-cycles[:uH]* -c)

The perf stat output on a s390 z/VM system is

 # perf stat -a -- sleep 0.1 2>&1
 Performance counter stats for 'system wide':

       56      context-switches  #     46.3 cs/sec  cs_per_second
 1,210.41 msec cpu-clock         #     11.9 CPUs  CPUs_utilized
       12      cpu-migrations    #      9.9 migrations/sec ...
       81      page-faults       #     66.9 faults/sec ...

       0.100891009 seconds time elapsed

The grep command does not match any single line and exits with error
code 1. As the bash script is executed with set -e, it aborts with the
first error code being non-zero.

Fix this and use wc -l to count matching lines instead of grep ... -c.

Output before:
 # perf test 102
 102: perf stat tests                      : FAILED!
 #
Output after:
 # perf test 102
 102: perf stat tests                      : Ok
 #

Fixes: bb6e7cb11d97c ("perf tools: Add fallback for exclude_guest")
Cc: James Clark <james.clark@linaro.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/shell/stat.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/shell/stat.sh b/tools/perf/tests/shell/stat.sh
index 0b2f0f88ca16..792a0b79f6b8 100755
--- a/tools/perf/tests/shell/stat.sh
+++ b/tools/perf/tests/shell/stat.sh
@@ -233,7 +233,7 @@ test_hybrid() {
   fi
 
   # Run default Perf stat
-  cycles_events=$(perf stat -a -- sleep 0.1 2>&1 | grep -E "/cpu-cycles/[uH]*|  cpu-cycles[:uH]*  " -c)
+  cycles_events=$(perf stat -a -- sleep 0.1 2>&1 | grep -E "/cpu-cycles/[uH]*|  cpu-cycles[:uH]*  "  | wc -l)
 
   # The expectation is that default output will have a cycles events on each
   # hybrid PMU. In situations with no cycles PMU events, like virtualized, this
-- 
2.52.0