[PATCH 3/5] perf sched: Fix thread reference leaks in timehist_get_thread()

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

timehist_get_thread() acquires a thread reference via
machine__findnew_thread() and an idle thread reference via
get_idle_thread() (which calls thread__get()).  Two error paths in
the idle_hist block return NULL without releasing these references:

 - When get_idle_thread() fails, the thread reference leaks.
 - When thread__priv(idle) returns NULL, both idle and thread leak.

Additionally, the idle thread reference acquired on the success path
is never released, leaking a reference on every sample when
--idle-hist is active.

Add thread__put() calls on both error paths and release the idle
reference after use on the success path.

Fixes: 5d8f17fb5822 ("perf sched timehist: Add -I/--idle-hist option")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/builtin-sched.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 4aa7833cae6e36b8..7bd61028327b39db 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -2546,12 +2546,16 @@ static struct thread *timehist_get_thread(struct perf_sched *sched,
 			idle = get_idle_thread(sample->cpu);
 			if (idle == NULL) {
 				pr_err("Failed to get idle thread for cpu %d.\n", sample->cpu);
+				thread__put(thread);
 				return NULL;
 			}
 
 			itr = thread__priv(idle);
-			if (itr == NULL)
+			if (itr == NULL) {
+				thread__put(idle);
+				thread__put(thread);
 				return NULL;
+			}
 
 			thread__put(itr->last_thread);
 			itr->last_thread = thread__get(thread);
@@ -2559,6 +2563,8 @@ static struct thread *timehist_get_thread(struct perf_sched *sched,
 			/* copy task callchain when entering to idle */
 			if (perf_sample__intval(sample, "next_pid") == 0)
 				save_idle_callchain(sched, itr, sample);
+
+			thread__put(idle);
 		}
 	}
 
-- 
2.54.0