Commit 084cd756 authored Feb 06, 2023 by Pietro Borrello Committed by Greg Kroah-Hartman Mar 11, 2023

sched/rt: pick_next_rt_entity(): check list_entry



[ Upstream commit 7c4a5b89a0b5a57a64b601775b296abf77a9fe97 ]

Commit 326587b8 ("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: 326587b8 ("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-b1a71bd1ac6b@diag.uniroma1.it


Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 0ff7ba5e

kernel/sched/rt.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -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);