[RFC PATCH v6 5/5] perf sched: prefer to use prev_state_char introduced in sched_switch

[Ze Gao <zegao2021@gmail.com>]

Since the sched_switch tracepoint introduces a new variable to
report sched-out task state in symbolic char, we prefer to use
it to spare from knowing internal implementations in kernel.

Also we keep the old parsing logic intact but sync the state char
array with the latest kernel.

Signed-off-by: Ze Gao <zegao@tencent.com>
---
 tools/perf/builtin-sched.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 5042874ba204..6f99a36206c9 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -837,7 +837,7 @@ replay_wakeup_event(struct perf_sched *sched,
 
 static inline char task_state_char(int state)
 {
-	static const char state_to_char[] = "RSDTtXZPI";
+	static const char state_to_char[] = "RSDTtXZPIp";
 	unsigned int bit = state ? ffs(state) : 0;
 
 	return bit < sizeof(state_to_char) - 1 ? state_to_char[bit] : '?';
@@ -846,9 +846,20 @@ static inline char task_state_char(int state)
 static inline char get_task_prev_state(struct evsel *evsel,
 				       struct perf_sample *sample)
 {
-	const int prev_state = evsel__intval(evsel, sample, "prev_state");
+	char prev_state_char;
+	int prev_state;
 
-	return task_state_char(prev_state);
+	/* prefer to use prev_state_char */
+	if (evsel__field(evsel, "prev_state_char"))
+		prev_state_char = (char) evsel__intval(evsel,
+				sample, "prev_state_char");
+	else {
+		prev_state = (int) evsel__intval(evsel,
+				sample, "prev_state");
+		prev_state_char = task_state_char(prev_state);
+	}
+
+	return prev_state_char;
 }
 
 static int replay_switch_event(struct perf_sched *sched,
@@ -2145,7 +2156,7 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
 		else if (r->last_time) {
 			u64 dt_wait = tprev - r->last_time;
 
-			if (r->last_state == 'R')
+			if (r->last_state == 'R' || r->last_state == 'p')
 				r->dt_preempt = dt_wait;
 			else if (r->last_state == 'D')
 				r->dt_iowait = dt_wait;
-- 
2.41.0