From: Tejun Heo Date: Tue, 12 May 2026 20:30:00 +0000 (-1000) Subject: sched_ext: Drop NONE early return in scx_disable_and_exit_task() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=39e25a2100604320e8d9df54c6c31258f7a3df29;p=thirdparty%2Fkernel%2Flinux.git sched_ext: Drop NONE early return in scx_disable_and_exit_task() d3e73a0808dd ("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: d3e73a0808dd ("sched_ext: Handle SCX_TASK_NONE in disable/switched_from paths") Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 9354da79e162..68120f679178 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -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))