From 30fb2b1e4d41a641a059f295a717ffa0e24307e7 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 16 Oct 2026 19:37:16 -1000 Subject: [PATCH] sched_ext: Fix the running task keeping its protection into bypass Protection ends when the scheduler enters bypass, so that bypass scheduling can cut every task's slice. scx_bypass() clears it for the queued tasks by cycling them, and strips the running task's in the same walk over rq->scx.runnable_list. The running task is never on that list. set_next_task_scx() takes it off and put_prev_task_scx() puts it back, so the strip never runs. A protected running task then keeps its slice into bypass, where the tick's attempts to cut it are refused. Strip the running task's protection outside the walk. Fixes: 9cfc6ab34a31 ("sched_ext: Add SCX_TASK_PROTECTED") Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- kernel/sched/ext/ext.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 2c213153bdab..d6689bf8e769 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -6318,6 +6318,16 @@ void scx_bypass(struct scx_sched *sch, bool bypass) continue; } + /* + * Bypass trumps protection. Cycling the queued tasks below + * clears theirs. The current task isn't on the runnable list, + * so strip its protection here. + */ + p = rq->curr; + if (bypass && p->sched_class == &ext_sched_class && + scx_is_descendant(scx_task_sched(p), sch)) + scx_task_slice_ended(rq, p); + /* * The use of list_for_each_entry_safe_reverse() is required * because each task is going to be removed from and added back @@ -6330,13 +6340,6 @@ void scx_bypass(struct scx_sched *sch, bool bypass) if (!scx_is_descendant(scx_task_sched(p), sch)) continue; - /* - * Bypass trumps protection. Cycling clears for queued - * tasks but current task needs explicit stripping. - */ - if (bypass && task_current(rq, p)) - scx_task_slice_ended(rq, p); - /* cycling deq/enq is enough, see the function comment */ scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE) { /* nothing */ ;