From nobody Sat Feb 7 16:26:23 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36AD9EB64DA for ; Sat, 24 Jun 2023 18:28:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232332AbjFXS2c (ORCPT ); Sat, 24 Jun 2023 14:28:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229623AbjFXS2a (ORCPT ); Sat, 24 Jun 2023 14:28:30 -0400 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62C581BC1 for ; Sat, 24 Jun 2023 11:28:28 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R371e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=cruzzhao@linux.alibaba.com;NM=1;PH=DS;RN=26;SR=0;TI=SMTPD_---0VlplJJJ_1687631295; Received: from rt2b04371.sqa.tbc.tbsite.net(mailfrom:CruzZhao@linux.alibaba.com fp:SMTPD_---0VlplJJJ_1687631295) by smtp.aliyun-inc.com; Sun, 25 Jun 2023 02:28:23 +0800 From: Cruz Zhao To: gregkh@linuxfoundation.org, jirislaby@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, paulmck@kernel.org, quic_neeraju@quicinc.com, joel@joelfernandes.org, josh@joshtriplett.org, boqun.feng@gmail.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang1.zhang@intel.com, jstultz@google.com, clingutla@codeaurora.org, nsaenzju@redhat.com, tglx@linutronix.de, frederic@kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2] sched/core: introduce sched_core_idle_cpu() Date: Sun, 25 Jun 2023 02:28:15 +0800 Message-Id: <1687631295-126383-1-git-send-email-CruzZhao@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" As core scheduling introduced, a new state of idle is defined as force idle, running idle task but nr_running greater than zero. If a cpu is in force idle state, idle_cpu() will return zero. This result makes sense in certain scenarios, e.g., load balance. but this will cause error in other scenarios, e.g., tick_irq_exit() will not change ts->idle_active back to 1 because idle_cpu() returns 0 when force idle. To solve this problem, we introduce sched_core_idle_cpu(), which returns 1 when force idle. We audit all users of idle_cpu(), and change idle_cpu() into sched_core_idle_cpu() in the following functions: - showacpu() - rcu_is_rcuc_kthread_starving() - tick_irq_exit() v1-->v2: replace idle_cpu() with sched_core_idle_cpu() in function showacpu() and rcu_is_rcuc_kthread_starving() Signed-off-by: Cruz Zhao --- drivers/tty/sysrq.c | 2 +- include/linux/sched.h | 2 ++ kernel/rcu/tree_stall.h | 2 +- kernel/sched/core.c | 13 +++++++++++++ kernel/softirq.c | 2 +- 5 files changed, 18 insertions(+), 3 deletions(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index b6e70c5cfa17..8a6586800385 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -232,7 +232,7 @@ static void showacpu(void *dummy) unsigned long flags; =20 /* Idle CPUs have no interesting backtrace. */ - if (idle_cpu(smp_processor_id())) { + if (sched_core_idle_cpu(smp_processor_id())) { pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id()); return; } diff --git a/include/linux/sched.h b/include/linux/sched.h index b09a83bfad8b..73e61c0f10a7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2430,9 +2430,11 @@ extern void sched_core_free(struct task_struct *tsk); extern void sched_core_fork(struct task_struct *p); extern int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type= type, unsigned long uaddr); +extern int sched_core_idle_cpu(int cpu); #else static inline void sched_core_free(struct task_struct *tsk) { } static inline void sched_core_fork(struct task_struct *p) { } +static inline int sched_core_idle_cpu(int cpu) { return idle_cpu(cpu); } #endif =20 extern void sched_set_stop_task(int cpu, struct task_struct *stop); diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index b10b8349bb2a..6169faf30ecd 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -418,7 +418,7 @@ static bool rcu_is_rcuc_kthread_starving(struct rcu_dat= a *rdp, unsigned long *jp return false; =20 cpu =3D task_cpu(rcuc); - if (cpu_is_offline(cpu) || idle_cpu(cpu)) + if (cpu_is_offline(cpu) || sched_core_idle_cpu(cpu)) return false; =20 j =3D jiffies - READ_ONCE(rdp->rcuc_activity); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 71c1a0f232b4..c80088956987 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7286,6 +7286,19 @@ struct task_struct *idle_task(int cpu) return cpu_rq(cpu)->idle; } =20 +#ifdef CONFIG_SCHED_CORE +int sched_core_idle_cpu(int cpu) +{ + struct rq *rq =3D cpu_rq(cpu); + + if (sched_core_enabled(rq) && rq->curr =3D=3D rq->idle) + return 1; + + return idle_cpu(cpu); +} + +#endif + #ifdef CONFIG_SMP /* * This function computes an effective utilization for the given CPU, to be diff --git a/kernel/softirq.c b/kernel/softirq.c index c8a6913c067d..98b98991ce45 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -630,7 +630,7 @@ static inline void tick_irq_exit(void) int cpu =3D smp_processor_id(); =20 /* Make sure that timer wheel updates are propagated */ - if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { + if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(c= pu)) { if (!in_hardirq()) tick_nohz_irq_exit(); } --=20 2.27.0