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sched_ext: Drop NONE early return in scx_disable_and_exit_task()

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d3e73a0808 ("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: d3e73a0808 ("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>
This commit is contained in:
Tejun Heo 2026-05-12 10:30:00 -10:00
parent 9a415cc537
commit 39e25a2100
1 changed files with 2 additions and 10 deletions
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12
kernel/sched/ext.c
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@ -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))