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sched_ext: Move reject DSQ draining into core

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The reject DSQ drain will be generalized for placement failures outside
sub-scheduler capability rejection. Move the drain into the core
sched_ext implementation first so the subsequent behavioral changes can
be reviewed separately. No functional change.

Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Andrea Righi 2026-09-22 18:51:47 +02:00 committed by Tejun Heo
parent 5f882051ef
commit cea8b60e4a
3 changed files with 50 additions and 54 deletions
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50
kernel/sched/ext/ext.c
View File

@ -4849,6 +4849,56 @@ static void process_deferred_reenq_users(struct rq *rq)
}
}
#ifdef CONFIG_EXT_SUB_SCHED
/*
* Drain @rq->scx.reject_dsq, reenqueueing each task so the BPF re-decides
* from p->scx.reenq_reason_*.
*
* A task can be re-rejected repeatedly. The reenqueue is bounded per task in
* scx_do_enqueue_task(), which ejects the owning sub past SCX_REENQ_MAX_REPEAT.
* Rejection can't happen for root.
*/
static void scx_reenq_reject(struct rq *rq)
{
LIST_HEAD(tasks);
struct task_struct *p, *n;
lockdep_assert_rq_held(rq);
if (!scx_has_subs() || list_empty(&rq->scx.reject_dsq.list))
return;
/*
* Move to a private list so a task re-rejected by the
* scx_do_enqueue_task() below isn't revisited this round.
*/
list_for_each_entry_safe(p, n, &rq->scx.reject_dsq.list, scx.dsq_list.node) {
/* migration_pending tasks should have bypassed to local DSQ */
if (WARN_ON_ONCE(p->migration_pending))
continue;
scx_reenq_wait_dispatching(p);
scx_dispatch_dequeue(rq, p);
if (WARN_ON_ONCE(p->scx.flags & SCX_TASK_REENQ_REASON_MASK))
p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
p->scx.flags |= SCX_TASK_REENQ_CAP;
list_add_tail(&p->scx.dsq_list.node, &tasks);
}
list_for_each_entry_safe(p, n, &tasks, scx.dsq_list.node) {
list_del_init(&p->scx.dsq_list.node);
scx_do_enqueue_task(rq, p, SCX_ENQ_REENQ, -1);
p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
}
}
#else
static void scx_reenq_reject(struct rq *rq) {}
#endif
static void run_deferred(struct rq *rq)
{
process_ddsp_deferred_locals(rq);

44
kernel/sched/ext/sub.c
View File

@ -772,50 +772,6 @@ bool scx_task_reenq_on_cap_revoke(struct rq *rq, struct task_struct *p)
return true;
}
/*
* Drain @rq->scx.reject_dsq, reenqueueing each task so the BPF re-decides
* from p->scx.reenq_reason_*.
*
* A task can be re-rejected repeatedly. The reenqueue is bounded per task in
* scx_do_enqueue_task(), which ejects the owning sub past SCX_REENQ_MAX_REPEAT.
* Rejection can't happen for root.
*/
void __scx_reenq_reject(struct rq *rq)
{
LIST_HEAD(tasks);
struct task_struct *p, *n;
if (list_empty(&rq->scx.reject_dsq.list))
return;
/*
* Move to a private list so a task re-rejected by the
* scx_do_enqueue_task() below isn't revisited this round.
*/
list_for_each_entry_safe(p, n, &rq->scx.reject_dsq.list, scx.dsq_list.node) {
/* migration_pending tasks should have bypassed to local DSQ */
if (WARN_ON_ONCE(p->migration_pending))
continue;
scx_reenq_wait_dispatching(p);
scx_dispatch_dequeue(rq, p);
if (WARN_ON_ONCE(p->scx.flags & SCX_TASK_REENQ_REASON_MASK))
p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
p->scx.flags |= SCX_TASK_REENQ_CAP;
list_add_tail(&p->scx.dsq_list.node, &tasks);
}
list_for_each_entry_safe(p, n, &tasks, scx.dsq_list.node) {
list_del_init(&p->scx.dsq_list.node);
scx_do_enqueue_task(rq, p, SCX_ENQ_REENQ, -1);
p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
}
}
/* record a caps change, see struct scx_caps_updated */
static void caps_updated_record(struct scx_pshard *ps, const struct scx_cmask *cids, u64 caps,
struct list_head *to_deliver)

10
kernel/sched/ext/sub.h
View File

@ -37,7 +37,6 @@ void scx_discard_stale_ecaps_syncs(void);
struct scx_dispatch_q *__scx_resolve_local_dsq(struct scx_sched *sch, struct rq *rq,
struct task_struct *p, u64 *enq_flags);
bool scx_task_reenq_on_cap_revoke(struct rq *rq, struct task_struct *p);
void __scx_reenq_reject(struct rq *rq);
void scx_rescue_charge(struct rq *rq, s64 delta_exec);
void scx_rescue_end(struct rq *rq);
bool scx_rescue_keep(struct rq *rq, struct task_struct *p);
@ -91,14 +90,6 @@ static inline struct scx_dispatch_q *scx_resolve_local_dsq(struct scx_sched *sch
return __scx_resolve_local_dsq(sch, rq, p, enq_flags);
}
static inline void scx_reenq_reject(struct rq *rq)
{
lockdep_assert_rq_held(rq);
if (scx_has_subs())
__scx_reenq_reject(rq);
}
#else /* CONFIG_EXT_SUB_SCHED */
static inline struct scx_sched *scx_next_descendant_pre(struct scx_sched *pos, struct scx_sched *root) { return pos ? NULL : root; }
@ -120,7 +111,6 @@ static inline void scx_discard_ecaps_to_sync(s32 cpu, struct scx_sched_pcpu *pcp
static inline void scx_discard_stale_ecaps_syncs(void) {}
static inline struct scx_dispatch_q *scx_resolve_local_dsq(struct scx_sched *sch, struct rq *rq, struct task_struct *p, u64 *enq_flags) { return &rq->scx.local_dsq; }
static inline bool scx_task_reenq_on_cap_revoke(struct rq *rq, struct task_struct *p) { return false; }
static inline void scx_reenq_reject(struct rq *rq) {}
static inline void scx_rescue_charge(struct rq *rq, s64 delta_exec) {}
static inline void scx_rescue_end(struct rq *rq) {}
static inline bool scx_rescue_keep(struct rq *rq, struct task_struct *p) { return false; }