This is a note to let you know that I've just added the patch titled sched/rt: pick_next_rt_entity(): check list_entry to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sched-rt-pick_next_rt_entity-check-list_entry.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a91503c3e97d70860e32442ff8effed0ba1494cd Author: Pietro Borrello <borrello@xxxxxxxxxxxxxxxx> Date: Mon Feb 6 22:33:54 2023 +0000 sched/rt: pick_next_rt_entity(): check list_entry [ Upstream commit 7c4a5b89a0b5a57a64b601775b296abf77a9fe97 ] Commit 326587b84078 ("sched: fix goto retry in pick_next_task_rt()") removed any path which could make pick_next_rt_entity() return NULL. However, BUG_ON(!rt_se) in _pick_next_task_rt() (the only caller of pick_next_rt_entity()) still checks the error condition, which can never happen, since list_entry() never returns NULL. Remove the BUG_ON check, and instead emit a warning in the only possible error condition here: the queue being empty which should never happen. Fixes: 326587b84078 ("sched: fix goto retry in pick_next_task_rt()") Signed-off-by: Pietro Borrello <borrello@xxxxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Phil Auld <pauld@xxxxxxxxxx> Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20230128-list-entry-null-check-sched-v3-1-b1a71bd1ac6b@xxxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ed2a47e4ddaec..0a11f44adee57 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1777,6 +1777,8 @@ static struct sched_rt_entity *pick_next_rt_entity(struct rt_rq *rt_rq) BUG_ON(idx >= MAX_RT_PRIO); queue = array->queue + idx; + if (SCHED_WARN_ON(list_empty(queue))) + return NULL; next = list_entry(queue->next, struct sched_rt_entity, run_list); return next; @@ -1789,7 +1791,8 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq) do { rt_se = pick_next_rt_entity(rt_rq); - BUG_ON(!rt_se); + if (unlikely(!rt_se)) + return NULL; rt_rq = group_rt_rq(rt_se); } while (rt_rq);