Commit 39e25a21 authored May 12, 2026 by Tejun Heo

sched_ext: Drop NONE early return in scx_disable_and_exit_task()



d3e73a08 ("sched_ext: Handle SCX_TASK_NONE in disable/switched_from
paths") skipped the trailing scx_set_task_sched(p, NULL) on NONE tasks.
After scx_fail_parent() parks a task at NONE/sched=parent and the parent
is later freed via queue_rcu_work() during root_disable, the preserved
p->scx.sched dangles - print_scx_info() from sched_show_task() reads
sch->ops.name from freed memory.

Drop the early return. __scx_disable_and_exit_task() already short-
circuits on NONE and the SUB_INIT block was cleared by
scx_fail_parent()'s earlier call, so clearing p->scx.sched is the only
work left - and the one thing the path actually needs.

v2: Extend the SUB_INIT block comment to note that the flag is only
    set on the sub-enable path, so it's always clear on the NONE
    re-entry (Andrea).

Fixes: d3e73a08 ("sched_ext: Handle SCX_TASK_NONE in disable/switched_from paths")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

parent 9a415cc5

kernel/sched/ext.c

+2 −10

Original line number	Diff line number	Diff line
		@@ -3703,22 +3703,14 @@ static void scx_sub_init_cancel_task(struct scx_sched sch, struct task_struct
		static void scx_disable_and_exit_task(struct scx_sched *sch,
		struct task_struct *p)
		{
		/*
		* %NONE means @p is already detached at the SCX level (e.g. handed
		* back to the parent by scx_fail_parent() with no init to undo).
		* Skip to avoid clobbering scx_task_sched() and writing %NONE again
		* on a state that's already %NONE.
		*/
		if (scx_get_task_state(p) == SCX_TASK_NONE)
		return;

		__scx_disable_and_exit_task(sch, p);

		/*
		* If set, @p exited between __scx_init_task() and scx_enable_task() in
		* scx_sub_enable() and is initialized for both the associated sched and
		* its parent. Exit for the child too - scx_enable_task() never ran for
		* it, so undo only init_task.
		* it, so undo only init_task. The flag is only set on the sub-enable
		* path, so it's always clear when @p arrives here in %SCX_TASK_NONE.
		*/
		if (p->scx.flags & SCX_TASK_SUB_INIT) {
		if (!WARN_ON_ONCE(!scx_enabling_sub_sched))