From: Tejun Heo Date: Fri, 6 Mar 2026 17:58:02 +0000 (-1000) Subject: sched_ext: Reorganize enable/disable path for multi-scheduler support X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dbd542a8fac7bcfba91e353f2a522e1bf2fbee27;p=thirdparty%2Fkernel%2Flinux.git 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_workfn() to scx_root_enable_workfn(). 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. v2: Keep scx_enable() name as-is and only rename the workfn to scx_root_enable_workfn(). Change scx_enable() return type to s32. Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index d42a22f5a098e..142845bcddaaa 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -3267,8 +3267,8 @@ 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; @@ -4430,24 +4430,12 @@ 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); @@ -4591,6 +4579,9 @@ static bool scx_claim_exit(struct scx_sched *sch, enum scx_exit_kind kind) lockdep_assert_preemption_disabled(); + 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; @@ -4603,21 +4594,31 @@ 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) { - guard(preempt)(); - scx_claim_exit(sch, kind); + scx_root_disable(sch); +} + +static void scx_disable(struct scx_sched *sch, enum scx_exit_kind kind) +{ + guard(preempt)(); + 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) @@ -5135,10 +5136,9 @@ struct scx_enable_cmd { int ret; }; -static void scx_enable_workfn(struct kthread_work *work) +static void scx_root_enable_workfn(struct kthread_work *work) { - struct scx_enable_cmd *cmd = - container_of(work, struct scx_enable_cmd, work); + struct scx_enable_cmd *cmd = container_of(work, struct scx_enable_cmd, work); struct sched_ext_ops *ops = cmd->ops; struct scx_sched *sch; struct scx_task_iter sti; @@ -5387,12 +5387,12 @@ err_disable: * 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); cmd->ret = 0; } -static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) +static s32 scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) { static struct kthread_worker *helper; static DEFINE_MUTEX(helper_mutex); @@ -5418,7 +5418,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) mutex_unlock(&helper_mutex); } - kthread_init_work(&cmd.work, scx_enable_workfn); + kthread_init_work(&cmd.work, scx_root_enable_workfn); cmd.ops = ops; kthread_queue_work(READ_ONCE(helper), &cmd.work); @@ -5561,7 +5561,7 @@ 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); } @@ -5689,7 +5689,15 @@ 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 = {