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Message-ID: <20260121231140.832332-7-tj@kernel.org>
Date: Wed, 21 Jan 2026 13:11:12 -1000
From: Tejun Heo <tj@...nel.org>
To: linux-kernel@...r.kernel.org,
sched-ext@...ts.linux.dev
Cc: void@...ifault.com,
andrea.righi@...ux.dev,
changwoo@...lia.com,
emil@...alapatis.com,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 06/34] sched_ext: Reorganize enable/disable path for multi-scheduler support
In preparation for multiple scheduler support, reorganize the enable and
disable paths to make scheduler instances explicit. Extract
scx_root_disable() from scx_disable_workfn(). Rename scx_enable() to
scx_root_enable(). Change scx_disable() to take @sch parameter and only
queue disable_work if scx_claim_exit() succeeds for consistency. Move
exit_kind validation into scx_claim_exit(). The sysrq handler now prints a
message when no scheduler is loaded.
These changes don't materially affect user-visible behavior.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/sched/ext.c | 73 ++++++++++++++++++++++++++--------------------
1 file changed, 41 insertions(+), 32 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index e61af4b0961c..c501ce2ca5f2 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3094,8 +3094,8 @@ void sched_ext_dead(struct task_struct *p)
raw_spin_unlock_irqrestore(&scx_tasks_lock, flags);
/*
- * @p is off scx_tasks and wholly ours. scx_enable()'s READY -> ENABLED
- * transitions can't race us. Disable ops for @p.
+ * @p is off scx_tasks and wholly ours. scx_root_enable()'s READY ->
+ * ENABLED transitions can't race us. Disable ops for @p.
*/
if (scx_get_task_state(p) != SCX_TASK_NONE) {
struct rq_flags rf;
@@ -4246,24 +4246,12 @@ static void free_kick_syncs(void)
}
}
-static void scx_disable_workfn(struct kthread_work *work)
+static void scx_root_disable(struct scx_sched *sch)
{
- struct scx_sched *sch = container_of(work, struct scx_sched, disable_work);
struct scx_exit_info *ei = sch->exit_info;
struct scx_task_iter sti;
struct task_struct *p;
- int kind, cpu;
-
- kind = atomic_read(&sch->exit_kind);
- while (true) {
- if (kind == SCX_EXIT_DONE) /* already disabled? */
- return;
- WARN_ON_ONCE(kind == SCX_EXIT_NONE);
- if (atomic_try_cmpxchg(&sch->exit_kind, &kind, SCX_EXIT_DONE))
- break;
- }
- ei->kind = kind;
- ei->reason = scx_exit_reason(ei->kind);
+ int cpu;
/* guarantee forward progress by bypassing scx_ops */
scx_bypass(true);
@@ -4398,6 +4386,9 @@ static bool scx_claim_exit(struct scx_sched *sch, enum scx_exit_kind kind)
{
int none = SCX_EXIT_NONE;
+ if (WARN_ON_ONCE(kind == SCX_EXIT_NONE || kind == SCX_EXIT_DONE))
+ kind = SCX_EXIT_ERROR;
+
if (!atomic_try_cmpxchg(&sch->exit_kind, &none, kind))
return false;
@@ -4410,20 +4401,30 @@ static bool scx_claim_exit(struct scx_sched *sch, enum scx_exit_kind kind)
return true;
}
-static void scx_disable(enum scx_exit_kind kind)
+static void scx_disable_workfn(struct kthread_work *work)
{
- struct scx_sched *sch;
+ struct scx_sched *sch = container_of(work, struct scx_sched, disable_work);
+ struct scx_exit_info *ei = sch->exit_info;
+ int kind;
- if (WARN_ON_ONCE(kind == SCX_EXIT_NONE || kind == SCX_EXIT_DONE))
- kind = SCX_EXIT_ERROR;
+ kind = atomic_read(&sch->exit_kind);
+ while (true) {
+ if (kind == SCX_EXIT_DONE) /* already disabled? */
+ return;
+ WARN_ON_ONCE(kind == SCX_EXIT_NONE);
+ if (atomic_try_cmpxchg(&sch->exit_kind, &kind, SCX_EXIT_DONE))
+ break;
+ }
+ ei->kind = kind;
+ ei->reason = scx_exit_reason(ei->kind);
- rcu_read_lock();
- sch = rcu_dereference(scx_root);
- if (sch) {
- scx_claim_exit(sch, kind);
+ scx_root_disable(sch);
+}
+
+static void scx_disable(struct scx_sched *sch, enum scx_exit_kind kind)
+{
+ if (scx_claim_exit(sch, kind))
kthread_queue_work(sch->helper, &sch->disable_work);
- }
- rcu_read_unlock();
}
static void dump_newline(struct seq_buf *s)
@@ -4927,13 +4928,13 @@ static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
return 0;
}
-static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
+static s32 scx_root_enable(struct sched_ext_ops *ops, struct bpf_link *link)
{
struct scx_sched *sch;
struct scx_task_iter sti;
struct task_struct *p;
unsigned long timeout;
- int i, cpu, ret;
+ s32 i, cpu, ret;
if (!cpumask_equal(housekeeping_cpumask(HK_TYPE_DOMAIN),
cpu_possible_mask)) {
@@ -5180,7 +5181,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
* Flush scx_disable_work to ensure that error is reported before init
* completion. sch's base reference will be put by bpf_scx_unreg().
*/
- scx_error(sch, "scx_enable() failed (%d)", ret);
+ scx_error(sch, "scx_root_enable() failed (%d)", ret);
kthread_flush_work(&sch->disable_work);
return 0;
}
@@ -5312,7 +5313,7 @@ static int bpf_scx_check_member(const struct btf_type *t,
static int bpf_scx_reg(void *kdata, struct bpf_link *link)
{
- return scx_enable(kdata, link);
+ return scx_root_enable(kdata, link);
}
static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
@@ -5320,7 +5321,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
struct sched_ext_ops *ops = kdata;
struct scx_sched *sch = ops->priv;
- scx_disable(SCX_EXIT_UNREG);
+ scx_disable(sch, SCX_EXIT_UNREG);
kthread_flush_work(&sch->disable_work);
kobject_put(&sch->kobj);
}
@@ -5448,7 +5449,15 @@ static struct bpf_struct_ops bpf_sched_ext_ops = {
static void sysrq_handle_sched_ext_reset(u8 key)
{
- scx_disable(SCX_EXIT_SYSRQ);
+ struct scx_sched *sch;
+
+ rcu_read_lock();
+ sch = rcu_dereference(scx_root);
+ if (likely(sch))
+ scx_disable(sch, SCX_EXIT_SYSRQ);
+ else
+ pr_info("sched_ext: BPF schedulers not loaded\n");
+ rcu_read_unlock();
}
static const struct sysrq_key_op sysrq_sched_ext_reset_op = {
--
2.52.0
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