[PATCH v2 16/16] perf synthetic-events: Fix divide by zero in perf_event__synthesize_threads

[Ian Rogers]

If scandir() finds no matching tasks in /proc, n is 0. If thread_nr is > 1,
we bypass the single-thread fast path and then clamp thread_nr to n, making
it 0. This results in a divide by zero when calculating num_per_thread.

Handle n <= 1 early to use the single-thread fast path and prevent the
crash.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/synthetic-events.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 35de41ad14d3..19c1f3eaf58d 100644
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -1058,7 +1058,7 @@ int perf_event__synthesize_threads(const struct perf_tool *tool,
 	else
 		thread_nr = nr_threads_synthesize;
 
-	if (thread_nr <= 1) {
+	if (thread_nr <= 1 || n <= 1) {
 		err = __perf_event__synthesize_threads(tool, process,
 						       machine,
 						       needs_mmap, mmap_data,
-- 
2.55.0.rc0.799.gd6f94ed593-goog