From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EA5F03815DD; Thu, 20 Aug 2026 15:18:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787239132; cv=none; b=hkgAHprJaBlosoD1epv50U0nqx8gaEkFmKQ2rswCECXGCi4X9BlmpXYlsa3vNL+VOwcLbiGwt8PMlDOKnErhPhxEl2Bn0rKbkwDp9SJOUOqnJMrAOOiqU7U4IouasxS4GupaFBlqH9xj/k1nLN5dZukvnechoJNrr6G8crR6QkQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787239132; c=relaxed/simple; bh=zqfj3SBZk8waWfdLoY5a27jjKgwmWjtHkxipEXVXqUI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OjWZcFPxrOhroYCDpOrAGEoONFWH4o7p4zN+kjVHR9hP1k6YnOU0s9FgbnpvYNM+HDztnfyO4fc1V3z6mxMUp6MUjSVwtGoF7BvspFbZ8IPMq9edIxC7xiR9cFpVEITzQEFv8PcnV+DrWqgdmQm9eGsdglnizOzPFFdQa+X6jZk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=iL5vU4Rc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="iL5vU4Rc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35B001F000E9; Thu, 20 Aug 2026 15:18:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787239129; bh=3cVRQ7V3lZtUUsIMJWwR+uiz4YULWH57uO39fKdUfqo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=iL5vU4RcMo/qv0LjJbbHfv+vGX+BCecnlxej7bO5YhJGzfxmL/CuWsKtCDf/Klyfq buZleMFPBxn2nOWnLL/I748o44Whqlm33rLaFku2nbZ/yWyy22V9/pLCn36CikH+Yl IOVU/Op3EDwGzq5PJfPLgoTArmT+ojejkQWsAVYg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tejun Heo , Andrea Righi , Sasha Levin Subject: [PATCH 6.18 158/217] sched_ext: Reorganize enable/disable path for multi-scheduler support Date: Thu, 20 Aug 2026 16:55:26 +0200 Message-ID: <20260820145242.510599570@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145237.531699751@linuxfoundation.org> References: <20260820145237.531699751@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo [ Upstream commit dbd542a8fac7bcfba91e353f2a522e1bf2fbee27 ] 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 Stable-dep-of: 5f8b69642d18 ("sched_ext: Take cgroup_lock() first in scx_cgroup_lock()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/sched/ext.c | 78 +++++++++++++++++++++++++++++------------------------ 1 file changed, 43 insertions(+), 35 deletions(-) --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -3029,8 +3029,8 @@ void sched_ext_free(struct task_struct * 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; @@ -3962,24 +3962,12 @@ static void free_kick_pseqs(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); @@ -4124,6 +4112,9 @@ static bool scx_claim_exit(struct scx_sc 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; @@ -4136,21 +4127,31 @@ static bool scx_claim_exit(struct scx_sc 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) @@ -4662,10 +4663,9 @@ 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; @@ -4915,12 +4915,12 @@ 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); @@ -4946,7 +4946,7 @@ static int scx_enable(struct sched_ext_o 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); @@ -5089,7 +5089,7 @@ static void bpf_scx_unreg(void *kdata, s 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); } @@ -5217,7 +5217,15 @@ static struct bpf_struct_ops bpf_sched_e 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 = {