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Subject[PATCH 5.13 065/223] perf sched: Fix record failure when CONFIG_SCHEDSTATS is not set
Date
From: Yang Jihong <yangjihong1@huawei.com>

[ Upstream commit b0f008551f0bf4d5f6db9b5f0e071b02790d6a2e ]

The tracepoints trace_sched_stat_{wait, sleep, iowait} are not exposed to user
if CONFIG_SCHEDSTATS is not set, "perf sched record" records the three events.
As a result, the command fails.

Before:

#perf sched record sleep 1
event syntax error: 'sched:sched_stat_wait'
\___ unknown tracepoint

Error: File /sys/kernel/tracing/events/sched/sched_stat_wait not found.
Hint: Perhaps this kernel misses some CONFIG_ setting to enable this feature?.

Run 'perf list' for a list of valid events

Usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]

-e, --event <event> event selector. use 'perf list' to list available events

Solution:
Check whether schedstat tracepoints are exposed. If no, these events are not recorded.

After:
# perf sched record sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.163 MB perf.data (1091 samples) ]
# perf sched report
run measurement overhead: 4736 nsecs
sleep measurement overhead: 9059979 nsecs
the run test took 999854 nsecs
the sleep test took 8945271 nsecs
nr_run_events: 716
nr_sleep_events: 785
nr_wakeup_events: 0
...
------------------------------------------------------------

Fixes: 2a09b5de235a6 ("sched/fair: do not expose some tracepoints to user if CONFIG_SCHEDSTATS is not set")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
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>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Yafang Shao <laoar.shao@gmail.com>
Link: http://lore.kernel.org/lkml/20210713112358.194693-1-yangjihong1@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/builtin-sched.c | 33 +++++++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 954ce2f594e9..3e5b7faf0c16 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -3335,6 +3335,16 @@ static void setup_sorting(struct perf_sched *sched, const struct option *options
sort_dimension__add("pid", &sched->cmp_pid);
}

+static bool schedstat_events_exposed(void)
+{
+ /*
+ * Select "sched:sched_stat_wait" event to check
+ * whether schedstat tracepoints are exposed.
+ */
+ return IS_ERR(trace_event__tp_format("sched", "sched_stat_wait")) ?
+ false : true;
+}
+
static int __cmd_record(int argc, const char **argv)
{
unsigned int rec_argc, i, j;
@@ -3346,21 +3356,33 @@ static int __cmd_record(int argc, const char **argv)
"-m", "1024",
"-c", "1",
"-e", "sched:sched_switch",
- "-e", "sched:sched_stat_wait",
- "-e", "sched:sched_stat_sleep",
- "-e", "sched:sched_stat_iowait",
"-e", "sched:sched_stat_runtime",
"-e", "sched:sched_process_fork",
"-e", "sched:sched_wakeup_new",
"-e", "sched:sched_migrate_task",
};
+
+ /*
+ * The tracepoints trace_sched_stat_{wait, sleep, iowait}
+ * are not exposed to user if CONFIG_SCHEDSTATS is not set,
+ * to prevent "perf sched record" execution failure, determine
+ * whether to record schedstat events according to actual situation.
+ */
+ const char * const schedstat_args[] = {
+ "-e", "sched:sched_stat_wait",
+ "-e", "sched:sched_stat_sleep",
+ "-e", "sched:sched_stat_iowait",
+ };
+ unsigned int schedstat_argc = schedstat_events_exposed() ?
+ ARRAY_SIZE(schedstat_args) : 0;
+
struct tep_event *waking_event;

/*
* +2 for either "-e", "sched:sched_wakeup" or
* "-e", "sched:sched_waking"
*/
- rec_argc = ARRAY_SIZE(record_args) + 2 + argc - 1;
+ rec_argc = ARRAY_SIZE(record_args) + 2 + schedstat_argc + argc - 1;
rec_argv = calloc(rec_argc + 1, sizeof(char *));

if (rec_argv == NULL)
@@ -3376,6 +3398,9 @@ static int __cmd_record(int argc, const char **argv)
else
rec_argv[i++] = strdup("sched:sched_wakeup");

+ for (j = 0; j < schedstat_argc; j++)
+ rec_argv[i++] = strdup(schedstat_args[j]);
+
for (j = 1; j < (unsigned int)argc; j++, i++)
rec_argv[i] = argv[j];

--
2.30.2


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