This fix is the deadline version of the change made to the rt scheduler here: https://lore.kernel.org/lkml/20250225180553.167995-1-harshit@xxxxxxxxxxx/ Please go through the original change for more details on the issue. In this fix we bail out or retry in the push_dl_task, if the task is no longer at the head of pushable tasks list because this list changed while trying to lock the runqueue of the other CPU. Signed-off-by: Harshit Agarwal <harshit@xxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- kernel/sched/deadline.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 38e4537790af..c5048969c640 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2704,6 +2704,7 @@ static int push_dl_task(struct rq *rq) { struct task_struct *next_task; struct rq *later_rq; + struct task_struct *task; int ret = 0; next_task = pick_next_pushable_dl_task(rq); @@ -2734,15 +2735,30 @@ static int push_dl_task(struct rq *rq) /* Will lock the rq it'll find */ later_rq = find_lock_later_rq(next_task, rq); - if (!later_rq) { - struct task_struct *task; + task = pick_next_pushable_dl_task(rq); + if (later_rq && (!task || task != next_task)) { + /* + * We must check all this again, since + * find_lock_later_rq releases rq->lock and it is + * then possible that next_task has migrated and + * is no longer at the head of the pushable list. + */ + double_unlock_balance(rq, later_rq); + if (!task) { + /* No more tasks */ + goto out; + } + put_task_struct(next_task); + next_task = task; + goto retry; + } + if (!later_rq) { /* * We must check all this again, since * find_lock_later_rq releases rq->lock and it is * then possible that next_task has migrated. */ - task = pick_next_pushable_dl_task(rq); if (task == next_task) { /* * The task is still there. We don't try @@ -2751,9 +2767,10 @@ static int push_dl_task(struct rq *rq) goto out; } - if (!task) + if (!task) { /* No more tasks */ goto out; + } put_task_struct(next_task); next_task = task; -- 2.22.3
