[PATCH v5 12/15] tools/perf/test: make perf test adopt to task comm size change

[Yafang Shao <laoar.shao@gmail.com>]

kernel test robot reported a perf-test failure after I extended task comm
size from 16 to 24. The failure as follows,

2021-10-13 18:00:46 sudo /usr/src/perf_selftests-x86_64-rhel-8.3-317419b91ef4eff4e2f046088201e4dc4065caa0/tools/perf/perf test 15
15: Parse sched tracepoints fields                                  : FAILED!

The reason is perf-test requires a fixed-size task comm. If we extend
task comm size to 24, it will not equil with the required size 16 in perf
test.

After some analyzation, I found perf itself can adopt to the size
change, for example, below is the output of perf-sched after I extend
comm size to 24 -

task    614 (            kthreadd:        84), nr_events: 1
task    615 (             systemd:       843), nr_events: 1
task    616 (     networkd-dispat:      1026), nr_events: 1
task    617 (             systemd:       846), nr_events: 1

$ cat /proc/843/comm
networkd-dispatcher

The task comm can be displayed correctly as expected.

Now that task comm can have a different size, then the test should accept
the two sizes as possible and pass if it is 16 or 24. In order to do
that, a new macro TASK_COMM_LEN_24 is introduced.

After this patch, the perf-test succeeds no matter task comm is 16 or
24 -

15: Parse sched tracepoints fields                                  : Ok

This patch is a preparation for the followup patch.

Reported-by: kernel test robot <oliver.sang@intel.com>
Suggested-by: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Petr Mladek <pmladek@suse.com>
---
 tools/include/linux/sched/task.h  |  1 +
 tools/perf/tests/evsel-tp-sched.c | 26 ++++++++++++++++++++------
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/tools/include/linux/sched/task.h b/tools/include/linux/sched/task.h
index 7657dd3e0e02..da49ac983ac6 100644
--- a/tools/include/linux/sched/task.h
+++ b/tools/include/linux/sched/task.h
@@ -2,5 +2,6 @@
 #define _TOOLS_PERF_LINUX_SCHED_TASK_H
 
 #define TASK_COMM_LEN_16 16
+#define TASK_COMM_LEN_24 24
 
 #endif  /* _TOOLS_PERF_LINUX_SCHED_TASK_H */
diff --git a/tools/perf/tests/evsel-tp-sched.c b/tools/perf/tests/evsel-tp-sched.c
index f9e34bd26cf3..cf4e0472e29e 100644
--- a/tools/perf/tests/evsel-tp-sched.c
+++ b/tools/perf/tests/evsel-tp-sched.c
@@ -1,11 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/err.h>
+#include <linux/sched/task.h>
 #include <traceevent/event-parse.h>
 #include "evsel.h"
 #include "tests.h"
 #include "debug.h"
 
-static int evsel__test_field(struct evsel *evsel, const char *name, int size, bool should_be_signed)
+static int evsel__test_field_alt(struct evsel *evsel, const char *name,
+				 int size, int alternate_size, bool should_be_signed)
 {
 	struct tep_format_field *field = evsel__field(evsel, name);
 	int is_signed;
@@ -23,15 +25,24 @@ static int evsel__test_field(struct evsel *evsel, const char *name, int size, bo
 		ret = -1;
 	}
 
-	if (field->size != size) {
-		pr_debug("%s: \"%s\" size (%d) should be %d!\n",
+	if (field->size != size && field->size != alternate_size) {
+		pr_debug("%s: \"%s\" size (%d) should be %d",
 			 evsel->name, name, field->size, size);
+		if (alternate_size > 0)
+			pr_debug(" or %d", alternate_size);
+		pr_debug("!\n");
 		ret = -1;
 	}
 
 	return ret;
 }
 
+static int evsel__test_field(struct evsel *evsel, const char *name,
+			     int size, bool should_be_signed)
+{
+	return evsel__test_field_alt(evsel, name, size, -1, should_be_signed);
+}
+
 int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtest __maybe_unused)
 {
 	struct evsel *evsel = evsel__newtp("sched", "sched_switch");
@@ -42,7 +53,8 @@ int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtes
 		return -1;
 	}
 
-	if (evsel__test_field(evsel, "prev_comm", 16, false))
+	if (evsel__test_field_alt(evsel, "prev_comm", TASK_COMM_LEN_16,
+				  TASK_COMM_LEN_24, false))
 		ret = -1;
 
 	if (evsel__test_field(evsel, "prev_pid", 4, true))
@@ -54,7 +66,8 @@ int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtes
 	if (evsel__test_field(evsel, "prev_state", sizeof(long), true))
 		ret = -1;
 
-	if (evsel__test_field(evsel, "next_comm", 16, false))
+	if (evsel__test_field_alt(evsel, "next_comm", TASK_COMM_LEN_16,
+				  TASK_COMM_LEN_24, false))
 		ret = -1;
 
 	if (evsel__test_field(evsel, "next_pid", 4, true))
@@ -72,7 +85,8 @@ int test__perf_evsel__tp_sched_test(struct test *test __maybe_unused, int subtes
 		return -1;
 	}
 
-	if (evsel__test_field(evsel, "comm", 16, false))
+	if (evsel__test_field_alt(evsel, "comm", TASK_COMM_LEN_16,
+				  TASK_COMM_LEN_24, false))
 		ret = -1;
 
 	if (evsel__test_field(evsel, "pid", 4, true))
-- 
2.17.1