perf sched replay: Fix -r/--repeat command line option for infinity

Currently, the -r/--repeat option accepts values from 0 and complains
for -1. The help section specifies:
-r, --repeat <n>      repeat the workload replay N times (-1: infinite)

The -r -1 option raises an error because replay_repeat is defined as
an unsigned int.

In the current implementation, the workload is repeated n times when
-r <n> is used, except when n is 0.

When -r is set to 0, the workload is also repeated once. This happens
because when -r=0, the run_one_test function is not called. (Note that
mutex unlocking, which is essential for child threads spawned to emulate
the workload, happens in run_one_test.) However, mutex unlocking is
still performed in the destroy_tasks function. Thus, -r=0 results in the
workload running once coincidentally.

To clarify and maintain the existing logic for -r >= 1 (which runs the
workload the specified number of times) and to fix the issue with infinite
runs, make -r=0 perform an infinite run.

Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20240628071821.15264-1-vineethr@linux.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

2 files changed, 11 insertions, 1 deletions

diff --git a/tools/perf/Documentation/perf-sched.txt b/tools/perf/Documentation/perf-sched.txt
index 74c812f7a4a4..f0e5617f6652 100644
--- a/tools/perf/Documentation/perf-sched.txt
+++ b/tools/perf/Documentation/perf-sched.txt
@@ -202,6 +202,13 @@ OPTIONS for 'perf sched timehist'
 --state::
 	Show task state when it switched out.
 
+OPTIONS for 'perf sched replay'
+------------------------------
+
+-r::
+--repeat <n>::
+	repeat the workload n times (0: infinite). Default is 10.
+
 SEE ALSO
 --------
 linkperf:perf-record[1]
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index aa59f763ca46..24e9d83c7bb6 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -3386,6 +3386,9 @@ static int perf_sched__replay(struct perf_sched *sched)
 	sched->thread_funcs_exit = false;
 	create_tasks(sched);
 	printf("------------------------------------------------------------\n");
+	if (sched->replay_repeat == 0)
+		sched->replay_repeat = UINT_MAX;
+
 	for (i = 0; i < sched->replay_repeat; i++)
 		run_one_test(sched);
 
@@ -3551,7 +3554,7 @@ int cmd_sched(int argc, const char **argv)
 	};
 	const struct option replay_options[] = {
 	OPT_UINTEGER('r', "repeat", &sched.replay_repeat,
-		     "repeat the workload replay N times (-1: infinite)"),
+		     "repeat the workload replay N times (0: infinite)"),
 	OPT_PARENT(sched_options)
 	};
 	const struct option map_options[] = {