From: Pietro Borrello borrello@diag.uniroma1.it
[ 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@diag.uniroma1.it Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Phil Auld pauld@redhat.com Reviewed-by: Steven Rostedt (Google) rostedt@goodmis.org Link: https://lore.kernel.org/r/20230128-list-entry-null-check-sched-v3-1-b1a71bd1... Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/rt.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index e5d42947e57ab..186e7d78ded5c 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1561,6 +1561,8 @@ 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; @@ -1573,7 +1575,8 @@ 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);