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From:   Thomas Richter <tmricht@linux.ibm.com>
To:     linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        acme@kernel.org
Cc:     brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, Thomas Richter <tmricht@linux.ibm.com>
Subject: [PATCH] perf test: Fix failure of test 14 on s390
Date:   Tue, 19 Feb 2019 16:36:39 +0100
Message-Id: <20190219153639.31267-1-tmricht@linux.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Commit 489338a717a0 ("perf tests evsel-tp-sched: Fix bitwise operator")
causes test case 14 "Parse sched tracepoints fields" to fail on s390.
This test succeeds on x86.
In fact this test now fails on all architectures with type char
treated as type unsigned char.

The root cause is the signed-ness of character arrays in the
tracepoints sched_switch for structure members prev_comm and
next_comm.

On s390 the output of
 [root@m35lp76 perf]# cat /sys/kernel/debug/tracing/events/\
				sched/sched_switch/format
 name: sched_switch
 ID: 287
 format:
   field:unsigned short common_type; offset:0; size:2;	signed:0;
   ...
   field:char prev_comm[16]; offset:8; size:16;	signed:0;
   ...
   field:char next_comm[16]; offset:40; size:16; signed:0;

reveals the character arrays prev_comm and next_comm are per
default unsigned char and have values in the range of 0..255.

On x86 both fields are signed as this output shows:
 [root@f29]# cat /sys/kernel/debug/tracing/events/sched/\
			sched_switch/format
 name: sched_switch
 ID: 287
 format:
   field:unsigned short common_type; offset:0; size:2;	signed:0;
   ...
   field:char prev_comm[16]; offset:8; size:16;	signed:1;
   ...
   field:char next_comm[16]; offset:40; size:16; signed:1;

and the character arrays prev_comm and next_comm are per
default signed char and have values in the range of -1..127.
The implementation of type char is architecture specific.

Since the character arrays in both tracepoints
sched_switch and sched_wakeup should contain ascii characters,
simply omit the check for signedness in the test case.

Output before:
[root@m35lp76 perf]# ./perf test -F 14
14: Parse sched tracepoints fields                        :
--- start ---
sched:sched_switch: "prev_comm" signedness(0) is wrong, should be 1
sched:sched_switch: "next_comm" signedness(0) is wrong, should be 1
sched:sched_wakeup: "comm" signedness(0) is wrong, should be 1
---- end ----
14: Parse sched tracepoints fields                        : FAILED!
[root@m35lp76 perf]#

Output after:
[root@m35lp76 perf]# ./perf test -Fv 14
14: Parse sched tracepoints fields                        :
--- start ---
---- end ----
Parse sched tracepoints fields: Ok
[root@m35lp76 perf]#

Fixes: 489338a717a0 ("perf tests evsel-tp-sched: Fix bitwise operator")

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/evsel-tp-sched.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/tests/evsel-tp-sched.c b/tools/perf/tests/evsel-tp-sched.c
index 5cbba70bcdd0..ea7acf403727 100644
--- a/tools/perf/tests/evsel-tp-sched.c
+++ b/tools/perf/tests/evsel-tp-sched.c
@@ -43,7 +43,7 @@ int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtes
 		return -1;
 	}
 
-	if (perf_evsel__test_field(evsel, "prev_comm", 16, true))
+	if (perf_evsel__test_field(evsel, "prev_comm", 16, false))
 		ret = -1;
 
 	if (perf_evsel__test_field(evsel, "prev_pid", 4, true))
@@ -55,7 +55,7 @@ int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtes
 	if (perf_evsel__test_field(evsel, "prev_state", sizeof(long), true))
 		ret = -1;
 
-	if (perf_evsel__test_field(evsel, "next_comm", 16, true))
+	if (perf_evsel__test_field(evsel, "next_comm", 16, false))
 		ret = -1;
 
 	if (perf_evsel__test_field(evsel, "next_pid", 4, true))
@@ -73,7 +73,7 @@ int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtes
 		return -1;
 	}
 
-	if (perf_evsel__test_field(evsel, "comm", 16, true))
+	if (perf_evsel__test_field(evsel, "comm", 16, false))
 		ret = -1;
 
 	if (perf_evsel__test_field(evsel, "pid", 4, true))
-- 
2.19.1