From 4a81d59a9d81e6db4e76f84a3d2638e64ff79533 Mon Sep 17 00:00:00 2001 From: Aaron Tomlin Date: Thu, 6 Aug 2026 11:39:23 -0400 Subject: [PATCH] perf sched: Suppress latency table output when trace samples are missing When 'perf sched latency' is executed on a perf.data file that lacks tracepoint samples (i.e., a file recorded without the -R flag or containing only non-tracepoint events), perf_session__has_traces() correctly outputs an error message. However, perf_sched__read_events() subsequently falls through and returns 0 (success). Consequently, caller functions such as perf_sched__lat() assume event processing succeeded and proceed to render empty latency header tables and total summary statistics. Fix this behaviour by ensuring perf_sched__read_events() aborts early and returns a suitable error code when perf_session__has_traces() evaluates to false. Additionally, validate thread__get_runtime() against NULL in map_switch_event() to prevent potential null-pointer dereferences. Fixes: 27295592c22e ("perf session: Share the common trace sample_check routine as perf_session__has_traces") Reviewed-by: Ian Rogers Signed-off-by: Aaron Tomlin Signed-off-by: Namhyung Kim --- tools/perf/builtin-sched.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c index acc8d81a20d3..39a375ef209a 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -1833,7 +1833,7 @@ static int map_switch_event(struct perf_sched *sched, struct perf_sample *sampl sched_out: if (sched->map.task_name) { tr = thread__get_runtime(sched->curr_out_thread[this_cpu.cpu]); - if (strcmp(tr->shortname, "") == 0) + if (tr == NULL || strcmp(tr->shortname, "") == 0) goto out; if (proceed == 1) @@ -2001,7 +2001,7 @@ static int perf_sched__read_events(struct perf_sched *sched) .mode = PERF_DATA_MODE_READ, .force = sched->force, }; - int rc = -1; + int rc = -1, err; session = perf_session__new(&data, &sched->tool); if (IS_ERR(session)) { @@ -2018,18 +2018,19 @@ static int perf_sched__read_events(struct perf_sched *sched) if (perf_session__set_tracepoints_handlers(session, handlers)) goto out_delete; - if (perf_session__has_traces(session, "record -R")) { - int err = perf_session__process_events(session); - if (err) { - pr_err("Failed to process events, error %d", err); - goto out_delete; - } + if (!perf_session__has_traces(session, "record -R")) + goto out_delete; - sched->nr_events = evlist__stats(session->evlist)->nr_events[0]; - sched->nr_lost_events = evlist__stats(session->evlist)->total_lost; - sched->nr_lost_chunks = evlist__stats(session->evlist)->nr_events[PERF_RECORD_LOST]; + err = perf_session__process_events(session); + if (err) { + pr_err("Failed to process events, error %d", err); + goto out_delete; } + sched->nr_events = evlist__stats(session->evlist)->nr_events[0]; + sched->nr_lost_events = evlist__stats(session->evlist)->total_lost; + sched->nr_lost_chunks = evlist__stats(session->evlist)->nr_events[PERF_RECORD_LOST]; + rc = 0; out_delete: perf_session__delete(session);