Commit d3e73a08 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Handle SCX_TASK_NONE in disable/switched_from paths 



scx_fail_parent() leaves cgroup tasks at (state=NONE, sched=parent,
sched_class=ext) until the parent itself is torn down by the scx_error() it
raised. When the later root_disable iterates them, two paths trip on NONE.

scx_disable_and_exit_task() re-enters the wrapper at NONE: the inner switch
returns early but the trailing scx_set_task_sched(p, NULL) clobbers the
parent sched left by scx_fail_parent(), and scx_set_task_state(p, NONE)
wastes a write on an already-NONE task. switched_from_scx() then calls
scx_disable_task(), which WARNs on non-ENABLED state and writes state=READY,
producing a NONE -> READY transition the validation matrix rejects.

Treat NONE as "nothing to do" in both paths. Add a NONE early-return at the
top of scx_disable_and_exit_task() and a parallel NONE check in
switched_from_scx() next to task_dead_and_done().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
parent cd6aab73

kernel/sched/ext.c

+19 −0
Original line number Diff line number Diff line
@@ -3703,6 +3703,15 @@ 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);



	/*
@@ -3921,6 +3930,16 @@ static void switched_from_scx(struct rq *rq, struct task_struct *p) 
	if (task_dead_and_done(p))

		return;



	/*

	 * %NONE means SCX is no longer tracking @p at the task level (e.g.

	 * scx_fail_parent() handed @p back to the parent at NONE pending the

	 * parent's own teardown). There is nothing to disable; calling

	 * scx_disable_task() would WARN on the non-%ENABLED state and trigger a

	 * NONE -> READY validation failure.

	 */

	if (scx_get_task_state(p) == SCX_TASK_NONE)

		return;



	scx_disable_task(scx_task_sched(p), p);

}