From nobody Tue Dec 2 01:51:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 EC98B33CEB7 for ; Thu, 20 Nov 2025 14:57:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650632; cv=none; b=Td5OvVOM+uAP8DR5sHflZK1VBT5+xRMVyVt9CILRB1kzpFmXkzwNgj4OdXVeZlNvXTFDqb1KK/TiCCnDByE5fCw/VxOXrJgd93G0sQE3Di5YFX2cIk6L63Kx/d/U8N2rb07lv/jFYjeZtX6Pr4o5G2vBWwSIkpBxNSOokhMDaQ0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650632; c=relaxed/simple; bh=O9zK34ymQ3KroWMW5Fi9ejCqmujGPuZ0x+pj68Q/DUE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KVzjTo4g3liQRoMloh0c3Hfr9hyBbWMSygo/doN5soLX/jPLtGH7r+t/GFssw/GpQhVBSl2d2D/RoLVtVP8Qg2lEVECv5+Q4aX2keCOEHuY00Gmjtnn7KuCtp0R5ME7zM4UO/CuvC/qcK1BhndaLMtYhtkSR/136RQwm5xPiRNI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=f5kIQd65; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="f5kIQd65" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763650628; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zND6J3nrdpEPxMayGU9dWtIyvlRFzw/cBOy+nF51860=; b=f5kIQd65ahZlyunbhO1s+AK4BJeUSd4uvbchNAsN3EfW4+BPHxpQmSb/NDniBRKvwRsv+N 8nu1klv7EORuUzT/qxXMkWh2TrYjpPq4RoUc2UUL1r2m7wS9ozf65ZgpHcBHmt97V0uxkx pF8Ip/NHYz2u4tmNK7cfNbOv3G18QpQ= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-116-HEhayZAiOkKMRRntAy_oCw-1; Thu, 20 Nov 2025 09:57:05 -0500 X-MC-Unique: HEhayZAiOkKMRRntAy_oCw-1 X-Mimecast-MFC-AGG-ID: HEhayZAiOkKMRRntAy_oCw_1763650624 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4290F195609D; Thu, 20 Nov 2025 14:57:04 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.239]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id AA4C51940E88; Thu, 20 Nov 2025 14:57:01 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v16 1/7] timers/migration: Rename 'online' bit to 'available' Date: Thu, 20 Nov 2025 15:56:47 +0100 Message-ID: <20251120145653.296659-2-gmonaco@redhat.com> In-Reply-To: <20251120145653.296659-1-gmonaco@redhat.com> References: <20251120145653.296659-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" The timer migration hierarchy excludes offline CPUs via the tmigr_is_not_available function, which is essentially checking the online bit for the CPU. Rename the online bit to available and all references in function names and tracepoint to generalise the concept of available CPUs. Reviewed-by: Frederic Weisbecker Reviewed-by: Thomas Gleixner Signed-off-by: Gabriele Monaco --- include/trace/events/timer_migration.h | 4 ++-- kernel/time/timer_migration.c | 24 ++++++++++++------------ kernel/time/timer_migration.h | 2 +- 3 files changed, 15 insertions(+), 15 deletions(-) diff --git a/include/trace/events/timer_migration.h b/include/trace/events/= timer_migration.h index 47db5eaf2f9a..61171b13c687 100644 --- a/include/trace/events/timer_migration.h +++ b/include/trace/events/timer_migration.h @@ -173,14 +173,14 @@ DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_active, TP_ARGS(tmc) ); =20 -DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_online, +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_available, =20 TP_PROTO(struct tmigr_cpu *tmc), =20 TP_ARGS(tmc) ); =20 -DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_offline, +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_unavailable, =20 TP_PROTO(struct tmigr_cpu *tmc), =20 diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 57e38674e56e..2cfebed35e22 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -429,7 +429,7 @@ static DEFINE_PER_CPU(struct tmigr_cpu, tmigr_cpu); =20 static inline bool tmigr_is_not_available(struct tmigr_cpu *tmc) { - return !(tmc->tmgroup && tmc->online); + return !(tmc->tmgroup && tmc->available); } =20 /* @@ -926,7 +926,7 @@ static void tmigr_handle_remote_cpu(unsigned int cpu, u= 64 now, * updated the event takes care when hierarchy is completely * idle. Otherwise the migrator does it as the event is enqueued. */ - if (!tmc->online || tmc->remote || tmc->cpuevt.ignore || + if (!tmc->available || tmc->remote || tmc->cpuevt.ignore || now < tmc->cpuevt.nextevt.expires) { raw_spin_unlock_irq(&tmc->lock); return; @@ -973,7 +973,7 @@ static void tmigr_handle_remote_cpu(unsigned int cpu, u= 64 now, * (See also section "Required event and timerqueue update after a * remote expiry" in the documentation at the top) */ - if (!tmc->online || !tmc->idle) { + if (!tmc->available || !tmc->idle) { timer_unlock_remote_bases(cpu); goto unlock; } @@ -1422,19 +1422,19 @@ static long tmigr_trigger_active(void *unused) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); =20 - WARN_ON_ONCE(!tmc->online || tmc->idle); + WARN_ON_ONCE(!tmc->available || tmc->idle); =20 return 0; } =20 -static int tmigr_cpu_offline(unsigned int cpu) +static int tmigr_clear_cpu_available(unsigned int cpu) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); int migrator; u64 firstexp; =20 raw_spin_lock_irq(&tmc->lock); - tmc->online =3D false; + tmc->available =3D false; WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 /* @@ -1442,7 +1442,7 @@ static int tmigr_cpu_offline(unsigned int cpu) * offline; Therefore nextevt value is set to KTIME_MAX */ firstexp =3D __tmigr_cpu_deactivate(tmc, KTIME_MAX); - trace_tmigr_cpu_offline(tmc); + trace_tmigr_cpu_unavailable(tmc); raw_spin_unlock_irq(&tmc->lock); =20 if (firstexp !=3D KTIME_MAX) { @@ -1453,7 +1453,7 @@ static int tmigr_cpu_offline(unsigned int cpu) return 0; } =20 -static int tmigr_cpu_online(unsigned int cpu) +static int tmigr_set_cpu_available(unsigned int cpu) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); =20 @@ -1462,11 +1462,11 @@ static int tmigr_cpu_online(unsigned int cpu) return -EINVAL; =20 raw_spin_lock_irq(&tmc->lock); - trace_tmigr_cpu_online(tmc); + trace_tmigr_cpu_available(tmc); tmc->idle =3D timer_base_is_idle(); if (!tmc->idle) __tmigr_cpu_activate(tmc); - tmc->online =3D true; + tmc->available =3D true; raw_spin_unlock_irq(&tmc->lock); return 0; } @@ -1758,7 +1758,7 @@ static int tmigr_add_cpu(unsigned int cpu) * The (likely) current CPU is expected to be online in the hierarchy, * otherwise the old root may not be active as expected. */ - WARN_ON_ONCE(!per_cpu_ptr(&tmigr_cpu, raw_smp_processor_id())->online); + WARN_ON_ONCE(!per_cpu_ptr(&tmigr_cpu, raw_smp_processor_id())->available= ); ret =3D tmigr_setup_groups(-1, old_root->numa_node, old_root, true); } =20 @@ -1854,7 +1854,7 @@ static int __init tmigr_init(void) goto err; =20 ret =3D cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_cpu_online, tmigr_cpu_offline); + tmigr_set_cpu_available, tmigr_clear_cpu_available); if (ret) goto err; =20 diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h index ae19f70f8170..70879cde6fdd 100644 --- a/kernel/time/timer_migration.h +++ b/kernel/time/timer_migration.h @@ -97,7 +97,7 @@ struct tmigr_group { */ struct tmigr_cpu { raw_spinlock_t lock; - bool online; 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Thu, 20 Nov 2025 14:57:07 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.239]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D4ECC1940E88; Thu, 20 Nov 2025 14:57:04 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v16 2/7] timers/migration: Add mask for CPUs available in the hierarchy Date: Thu, 20 Nov 2025 15:56:48 +0100 Message-ID: <20251120145653.296659-3-gmonaco@redhat.com> In-Reply-To: <20251120145653.296659-1-gmonaco@redhat.com> References: <20251120145653.296659-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" Keep track of the CPUs available for timer migration in a cpumask. This prepares the ground to generalise the concept of unavailable CPUs. Reviewed-by: Frederic Weisbecker Reviewed-by: Thomas Gleixner Signed-off-by: Gabriele Monaco --- kernel/time/timer_migration.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 2cfebed35e22..3325ca7989b3 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -424,6 +424,12 @@ static struct tmigr_group *tmigr_root; =20 static DEFINE_PER_CPU(struct tmigr_cpu, tmigr_cpu); =20 +/* + * CPUs available for timer migration. + * Protected by cpuset_mutex (with cpus_read_lock held) or cpus_write_lock. + */ +static cpumask_var_t tmigr_available_cpumask; + #define TMIGR_NONE 0xFF #define BIT_CNT 8 =20 @@ -1433,6 +1439,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu) int migrator; u64 firstexp; =20 + cpumask_clear_cpu(cpu, tmigr_available_cpumask); raw_spin_lock_irq(&tmc->lock); tmc->available =3D false; WRITE_ONCE(tmc->wakeup, KTIME_MAX); @@ -1446,7 +1453,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu) raw_spin_unlock_irq(&tmc->lock); =20 if (firstexp !=3D KTIME_MAX) { - migrator =3D cpumask_any_but(cpu_online_mask, cpu); + migrator =3D cpumask_any(tmigr_available_cpumask); work_on_cpu(migrator, tmigr_trigger_active, NULL); } =20 @@ -1461,6 +1468,7 @@ static int tmigr_set_cpu_available(unsigned int cpu) if (WARN_ON_ONCE(!tmc->tmgroup)) return -EINVAL; =20 + cpumask_set_cpu(cpu, tmigr_available_cpumask); raw_spin_lock_irq(&tmc->lock); trace_tmigr_cpu_available(tmc); tmc->idle =3D timer_base_is_idle(); @@ -1805,6 +1813,11 @@ static int __init tmigr_init(void) if (ncpus =3D=3D 1) return 0; =20 + if (!zalloc_cpumask_var(&tmigr_available_cpumask, GFP_KERNEL)) { + ret =3D -ENOMEM; + goto err; + } + /* * Calculate the required hierarchy levels. Unfortunately there is no * reliable information available, unless all possible CPUs have been --=20 2.51.1 From nobody Tue Dec 2 01:51:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 4E94E33A6F9 for ; Thu, 20 Nov 2025 14:57:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650638; cv=none; b=TeHbX1o5dFRS5Wg55wOvuGcqEKT0z+QsMiTE6kjYxoyHV59tKWYwRE9f3vUqUC/5NxP170fQ9+B5lpsRTmKe4BNFD0FC4k6zl3WhpZ954WpaebCrctnoTSakIiTG4PZp3cWIaXdu+Cv4xy4tDnNeLEpsklFgV9aOiLozanlkM3I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650638; c=relaxed/simple; bh=b14RG0XYqjWcOED2oSjxVhPsIYGUmwD/uPDUZoe7oS8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EKYZiulQ346HDOqJql082Q4efo8haJOHCUV0cF2AA5eeJXZu+yB9AcVpEJb5cJvsJr1wrKqBuUbpDgs8bJfaQrUDoMRfo0Vb41hDRQoeYH3lBJdeF06MqkHmyLNuFPztn5YK9IdFrHpiqPmq+R12OkpHOIKT6Aft0Mmg05bXcPU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=TKnj+ZNP; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TKnj+ZNP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763650636; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ner/7T7d8Fx26irSF8IiJ7glEDYHPZwkpOLYpKfYhYg=; b=TKnj+ZNPurPRrr5GjCsolWi6tttlKlQsoTjG4DoSKTyNhDaQGZtoOV4uFFxpiWfRntwL2K /k5Xf4Oz4KbE6zwWIu5sxS0FJdXOji+4c4WovWqWnR3BCfH+8PaPFyEymKykujDkcaUKn0 H27wRZjkq7WetUHQt4CNjb2Ie70Q8oM= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-457-_OvOBUN1P3CouIEMdvtqew-1; Thu, 20 Nov 2025 09:57:11 -0500 X-MC-Unique: _OvOBUN1P3CouIEMdvtqew-1 X-Mimecast-MFC-AGG-ID: _OvOBUN1P3CouIEMdvtqew_1763650630 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AFC35180048E; Thu, 20 Nov 2025 14:57:10 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.239]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0E9F51940E88; Thu, 20 Nov 2025 14:57:07 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v16 3/7] timers/migration: Use scoped_guard on available flag set/clear Date: Thu, 20 Nov 2025 15:56:49 +0100 Message-ID: <20251120145653.296659-4-gmonaco@redhat.com> In-Reply-To: <20251120145653.296659-1-gmonaco@redhat.com> References: <20251120145653.296659-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" Cleanup tmigr_clear_cpu_available() and tmigr_set_cpu_available() to prepare for easier checks on the available flag. Reviewed-by: Frederic Weisbecker Reviewed-by: Thomas Gleixner Signed-off-by: Gabriele Monaco --- kernel/time/timer_migration.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 3325ca7989b3..a01c7f8bdf52 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -1440,17 +1440,17 @@ static int tmigr_clear_cpu_available(unsigned int c= pu) u64 firstexp; =20 cpumask_clear_cpu(cpu, tmigr_available_cpumask); - raw_spin_lock_irq(&tmc->lock); - tmc->available =3D false; - WRITE_ONCE(tmc->wakeup, KTIME_MAX); + scoped_guard(raw_spinlock_irq, &tmc->lock) { + tmc->available =3D false; + WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 - /* - * CPU has to handle the local events on his own, when on the way to - * offline; Therefore nextevt value is set to KTIME_MAX - */ - firstexp =3D __tmigr_cpu_deactivate(tmc, KTIME_MAX); - trace_tmigr_cpu_unavailable(tmc); - raw_spin_unlock_irq(&tmc->lock); + /* + * CPU has to handle the local events on his own, when on the way to + * offline; Therefore nextevt value is set to KTIME_MAX + */ + firstexp =3D __tmigr_cpu_deactivate(tmc, KTIME_MAX); + trace_tmigr_cpu_unavailable(tmc); + } =20 if (firstexp !=3D KTIME_MAX) { migrator =3D cpumask_any(tmigr_available_cpumask); @@ -1469,13 +1469,13 @@ static int tmigr_set_cpu_available(unsigned int cpu) return -EINVAL; =20 cpumask_set_cpu(cpu, tmigr_available_cpumask); - raw_spin_lock_irq(&tmc->lock); - trace_tmigr_cpu_available(tmc); - tmc->idle =3D timer_base_is_idle(); - if (!tmc->idle) - __tmigr_cpu_activate(tmc); - tmc->available =3D true; - raw_spin_unlock_irq(&tmc->lock); + scoped_guard(raw_spinlock_irq, &tmc->lock) { + trace_tmigr_cpu_available(tmc); + tmc->idle =3D timer_base_is_idle(); + if (!tmc->idle) + __tmigr_cpu_activate(tmc); + tmc->available =3D true; + } return 0; } =20 --=20 2.51.1 From nobody Tue Dec 2 01:51:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 3774E34A3D6 for ; 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charset="utf-8" update_unbound_workqueue_cpumask() updates unbound workqueues settings when there's a change in isolated CPUs, but it can be used for other subsystems requiring updated when isolated CPUs change. Generalise the name to update_isolation_cpumasks() to prepare for other functions unrelated to workqueues to be called in that spot. [longman: Change the function name to update_isolation_cpumasks()] Acked-by: Frederic Weisbecker Acked-by: Waiman Long Signed-off-by: Gabriele Monaco Signed-off-by: Waiman Long Reviewed-by: Chen Ridong --- kernel/cgroup/cpuset.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 27adb04df675..cf34623fe66f 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1339,7 +1339,7 @@ static bool partition_xcpus_del(int old_prs, struct c= puset *parent, return isolcpus_updated; } =20 -static void update_unbound_workqueue_cpumask(bool isolcpus_updated) +static void update_isolation_cpumasks(bool isolcpus_updated) { int ret; =20 @@ -1470,7 +1470,7 @@ static int remote_partition_enable(struct cpuset *cs,= int new_prs, list_add(&cs->remote_sibling, &remote_children); cpumask_copy(cs->effective_xcpus, tmp->new_cpus); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_isolation_cpumasks(isolcpus_updated); cpuset_force_rebuild(); cs->prs_err =3D 0; =20 @@ -1511,7 +1511,7 @@ static void remote_partition_disable(struct cpuset *c= s, struct tmpmasks *tmp) compute_effective_exclusive_cpumask(cs, NULL, NULL); reset_partition_data(cs); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_isolation_cpumasks(isolcpus_updated); cpuset_force_rebuild(); =20 /* @@ -1580,7 +1580,7 @@ static void remote_cpus_update(struct cpuset *cs, str= uct cpumask *xcpus, if (xcpus) cpumask_copy(cs->exclusive_cpus, xcpus); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_isolation_cpumasks(isolcpus_updated); if (adding || deleting) cpuset_force_rebuild(); =20 @@ -1943,7 +1943,7 @@ static int update_parent_effective_cpumask(struct cpu= set *cs, int cmd, WARN_ON_ONCE(parent->nr_subparts < 0); } spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_isolation_cpumasks(isolcpus_updated); =20 if ((old_prs !=3D new_prs) && (cmd =3D=3D partcmd_update)) update_partition_exclusive_flag(cs, new_prs); @@ -2968,7 +2968,7 @@ static int update_prstate(struct cpuset *cs, int new_= prs) else if (isolcpus_updated) isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_isolation_cpumasks(isolcpus_updated); =20 /* Force update if switching back to member & update effective_xcpus */ update_cpumasks_hier(cs, &tmpmask, !new_prs); --=20 2.51.1 From nobody Tue Dec 2 01:51:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 4AE1D34AB06 for ; Thu, 20 Nov 2025 14:57:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650644; cv=none; b=HAGlv4T7rH/tpNYqaqDh/iPhArlVaWahz1jq6FlmOeDgc8zfEdEEcm8tAucXWvHa6u40858yl26fXKz3Z48dJMUsRhtg6gdY1c1V1yGCEexs8OqXVP4gvoLFgd0WqKZiDK3ALxC902Yw8w3bLBZoM5JTQE8k1j++5hZk4bEMypY= ARC-Message-Signature: i=1; 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Thu, 20 Nov 2025 14:57:17 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.239]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1AACA1940E82; Thu, 20 Nov 2025 14:57:14 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v16 5/7] sched/isolation: Force housekeeping if isolcpus and nohz_full don't leave any Date: Thu, 20 Nov 2025 15:56:51 +0100 Message-ID: <20251120145653.296659-6-gmonaco@redhat.com> In-Reply-To: <20251120145653.296659-1-gmonaco@redhat.com> References: <20251120145653.296659-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" Currently the user can set up isolcpus and nohz_full in such a way that leaves no housekeeping CPU (i.e. no CPU that is neither domain isolated nor nohz full). This can be a problem for other subsystems (e.g. the timer wheel imgration). Prevent this configuration by invalidating the last setting in case the union of isolcpus (domain) and nohz_full covers all CPUs. Reviewed-by: Waiman Long Reviewed-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/sched/isolation.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index a4cf17b1fab0..3ad0d6df6a0a 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -167,6 +167,29 @@ static int __init housekeeping_setup(char *str, unsign= ed long flags) } } =20 + /* + * Check the combination of nohz_full and isolcpus=3Ddomain, + * necessary to avoid problems with the timer migration + * hierarchy. managed_irq is ignored by this check since it + * isn't considered in the timer migration logic. + */ + iter_flags =3D housekeeping.flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMA= IN); + type =3D find_first_bit(&iter_flags, HK_TYPE_MAX); + /* + * Pass the check if none of these flags were previously set or + * are not in the current selection. + */ + iter_flags =3D flags & (HK_FLAG_KERNEL_NOISE | HK_FLAG_DOMAIN); + first_cpu =3D (type =3D=3D HK_TYPE_MAX || !iter_flags) ? 0 : + cpumask_first_and_and(cpu_present_mask, + housekeeping_staging, housekeeping.cpumasks[type]); + if (first_cpu >=3D min(nr_cpu_ids, setup_max_cpus)) { + pr_warn("Housekeeping: must include one present CPU " + "neither in nohz_full=3D nor in isolcpus=3Ddomain, " + "ignoring setting %s\n", str); + goto free_housekeeping_staging; + } + iter_flags =3D flags & ~housekeeping.flags; =20 for_each_set_bit(type, &iter_flags, HK_TYPE_MAX) --=20 2.51.1 From nobody Tue Dec 2 01:51:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 181ED34B18C for ; Thu, 20 Nov 2025 14:57:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650648; cv=none; b=Tn0MQNWYOKwhsIKVWrs8wzY9yfoZdTnJC9I6aY1H0SnIQualDackM4skqGXUvkE9i0+LaFpYlZ53O3fXl4aPW29wFk8evvvMc4qTqcHbhuAKVAT0iQfIq54s4r5TIKcP1bcmG+rajHqoxcFDKJUx/Guuj0v8Cwq2Qac8YWBkny4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650648; c=relaxed/simple; bh=GjD9QEs7SzmnvHl3zPU+QeUV23iO3Qc9hI+AkOrFEL0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AceQyTe+LS9POVHQRYG/qnWN8Ol8qq36ZLE1VyoYSY5XUR2PffsR3xx/0uGI4X9iAU325vcBq1Ee7Esh3UzcWlQzyD/9F4coMocvsMUHWTma/hHUeAWqIqM56NdaMwAEh2dWcjf1uVron2mb+Le8/0YfiOZQp6Pc8fG5K5oD4Ek= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Dpu/ieQV; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Dpu/ieQV" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763650646; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M2+7kEHxFbK67aWdgfs3yD8hYiWGLMLm6j7NkVaF+ig=; b=Dpu/ieQVr8iOhVZ/KY1DUjJJchplfapP8032J7h/wgXSH/WZq6qxazxhiaittDPclZB1GY Buod9wMpXEMCvF1vvwkECALYSKPXBv8XObOpuCBLhX0fXCzKLc3vYvD/Svb3fFaSjAyxv3 vcHqmQmRvzQLjKvyHVS7uKwjrTiGyNk= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-184-UucdNpW6PJ6dnkWHQVC0Qw-1; Thu, 20 Nov 2025 09:57:22 -0500 X-MC-Unique: UucdNpW6PJ6dnkWHQVC0Qw-1 X-Mimecast-MFC-AGG-ID: UucdNpW6PJ6dnkWHQVC0Qw_1763650641 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 53A3B1800451; Thu, 20 Nov 2025 14:57:21 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.239]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 741311940E82; Thu, 20 Nov 2025 14:57:18 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Yury Norov , Gabriele Monaco Subject: [PATCH v16 6/7] cpumask: Add initialiser to use cleanup helpers Date: Thu, 20 Nov 2025 15:56:52 +0100 Message-ID: <20251120145653.296659-7-gmonaco@redhat.com> In-Reply-To: <20251120145653.296659-1-gmonaco@redhat.com> References: <20251120145653.296659-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" From: Yury Norov Now we can simplify a code that allocates cpumasks for local needs. Automatic variables have to be initialized at declaration, or at least before any possibility for the logic to return, so that compiler wouldn't try to call an associate destructor function on a random stack number. Because cpumask_var_t, depending on the CPUMASK_OFFSTACK config, is either a pointer or an array, we have to have a macro for initialization. So define a CPUMASK_VAR_NULL macro, which allows to init struct cpumask pointer with NULL when CPUMASK_OFFSTACK is enabled, and effectively a no-op when CPUMASK_OFFSTACK is disabled (initialisation optimised out with -O2). Signed-off-by: Yury Norov Signed-off-by: Gabriele Monaco Reviewed-by: Frederic Weisbecker --- include/linux/cpumask.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index ff8f41ab7ce6..68be522449ec 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1005,6 +1005,7 @@ static __always_inline unsigned int cpumask_size(void) =20 #define this_cpu_cpumask_var_ptr(x) this_cpu_read(x) #define __cpumask_var_read_mostly __read_mostly +#define CPUMASK_VAR_NULL NULL =20 bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node); =20 @@ -1051,6 +1052,7 @@ static __always_inline bool cpumask_available(cpumask= _var_t mask) =20 #define this_cpu_cpumask_var_ptr(x) this_cpu_ptr(x) #define __cpumask_var_read_mostly +#define CPUMASK_VAR_NULL {} =20 static __always_inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t f= lags) { --=20 2.51.1 From nobody Tue Dec 2 01:51:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 88A1234AB06 for ; Thu, 20 Nov 2025 14:57:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650652; cv=none; b=KqrtL7ilk9WKnuETf+4SOyqSxCZV/wc8cj7qUjhUPNmBxmRJdSrL3S5o9ZGG1RV7kW45W9dksSd2eW5MNRG18iSOUPcmIafdwyDm9+5SDR/8JFaIPBq9qaopGKJtWSYvrrtdLS7NYb2CBu6nm3Yt/rW0cwr3yO+huMKUUytmgx8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763650652; c=relaxed/simple; bh=MBqulWxhzCg7tTSjhaBDfM0FVbGGkEXZ+OcNH7h6AAE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mXzGB0X2ap0Yul5uBXK64lLZnHCOYqxGdDbbVD6xkHp8jtGEhtoiEGt5EhpIHc78PLoo7cS67gGz+otlELL5Y5tDkysu2XtP64Egxz051xjZd+qsm5ktlvJJqUdE6btmxF4Bk1/ZVb4VlLLTawzPCuuSbCJEWVNMWuymGUT/yWU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Uju+ND70; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Uju+ND70" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763650649; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=K5GVdwYLSWSD+P3UHz0vpKR8IPFFO0pks0u5J755EOY=; b=Uju+ND70TCfP6TdTAa5XXOZk8JK8ZNtBgelR6GH3FfmWf6nu7P4xiq2dfb6q19F7jlRCIo t11VC+rsBU+YTySGOW27bLxPXfaSQrpwa7w9+3UbvMq7VPoxqV4Qm3YH0NV3+uhC1/fhqI 8RBsfo5MSkCTkp9S+HJHbKkxKc+QJck= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-643-IU1R8PINPv6i0GlRLcI6Ow-1; Thu, 20 Nov 2025 09:57:26 -0500 X-MC-Unique: IU1R8PINPv6i0GlRLcI6Ow-1 X-Mimecast-MFC-AGG-ID: IU1R8PINPv6i0GlRLcI6Ow_1763650645 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0E91419560AF; Thu, 20 Nov 2025 14:57:25 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.csb (unknown [10.45.224.239]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D4D2D1940E88; Thu, 20 Nov 2025 14:57:21 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco , "John B. Wyatt IV" , "John B. Wyatt IV" Subject: [PATCH v16 7/7] timers/migration: Exclude isolated cpus from hierarchy Date: Thu, 20 Nov 2025 15:56:53 +0100 Message-ID: <20251120145653.296659-8-gmonaco@redhat.com> In-Reply-To: <20251120145653.296659-1-gmonaco@redhat.com> References: <20251120145653.296659-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" The timer migration mechanism allows active CPUs to pull timers from idle ones to improve the overall idle time. This is however undesired when CPU intensive workloads run on isolated cores, as the algorithm would move the timers from housekeeping to isolated cores, negatively affecting the isolation. Exclude isolated cores from the timer migration algorithm, extend the concept of unavailable cores, currently used for offline ones, to isolated ones: * A core is unavailable if isolated or offline; * A core is available if non isolated and online; A core is considered unavailable as isolated if it belongs to: * the isolcpus (domain) list * an isolated cpuset Except if it is: * in the nohz_full list (already idle for the hierarchy) * the nohz timekeeper core (must be available to handle global timers) CPUs are added to the hierarchy during late boot, excluding isolated ones, the hierarchy is also adapted when the cpuset isolation changes. Due to how the timer migration algorithm works, any CPU part of the hierarchy can have their global timers pulled by remote CPUs and have to pull remote timers, only skipping pulling remote timers would break the logic. For this reason, prevent isolated CPUs from pulling remote global timers, but also the other way around: any global timer started on an isolated CPU will run there. This does not break the concept of isolation (global timers don't come from outside the CPU) and, if considered inappropriate, can usually be mitigated with other isolation techniques (e.g. IRQ pinning). This effect was noticed on a 128 cores machine running oslat on the isolated cores (1-31,33-63,65-95,97-127). The tool monopolises CPUs, and the CPU with lowest count in a timer migration hierarchy (here 1 and 65) appears as always active and continuously pulls global timers, from the housekeeping CPUs. This ends up moving driver work (e.g. delayed work) to isolated CPUs and causes latency spikes: before the change: # oslat -c 1-31,33-63,65-95,97-127 -D 62s ... Maximum: 1203 10 3 4 ... 5 (us) after the change: # oslat -c 1-31,33-63,65-95,97-127 -D 62s ... Maximum: 10 4 3 4 3 ... 5 (us) The same behaviour was observed on a machine with as few as 20 cores / 40 threads with isocpus set to: 1-9,11-39 with rtla-osnoise-top. Tested-by: John B. Wyatt IV Tested-by: John B. Wyatt IV Signed-off-by: Gabriele Monaco Reviewed-by: Frederic Weisbecker Reviewed-by: Thomas Gleixner --- include/linux/timer.h | 9 +++ kernel/cgroup/cpuset.c | 3 + kernel/time/timer_migration.c | 142 ++++++++++++++++++++++++++++++++++ 3 files changed, 154 insertions(+) diff --git a/include/linux/timer.h b/include/linux/timer.h index 0414d9e6b4fc..62e1cea71125 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -188,4 +188,13 @@ int timers_dead_cpu(unsigned int cpu); #define timers_dead_cpu NULL #endif =20 +#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) +extern int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask); +#else +static inline int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_c= pumask) +{ + return 0; +} +#endif + #endif diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index cf34623fe66f..bfc3b319e1c0 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1350,6 +1350,9 @@ static void update_isolation_cpumasks(bool isolcpus_u= pdated) =20 ret =3D workqueue_unbound_exclude_cpumask(isolated_cpus); WARN_ON_ONCE(ret < 0); + + ret =3D tmigr_isolated_exclude_cpumask(isolated_cpus); + WARN_ON_ONCE(ret < 0); } =20 /** diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index a01c7f8bdf52..4c5f2a576e13 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -10,6 +10,7 @@ #include #include #include +#include =20 #include "timer_migration.h" #include "tick-internal.h" @@ -427,8 +428,13 @@ static DEFINE_PER_CPU(struct tmigr_cpu, tmigr_cpu); /* * CPUs available for timer migration. * Protected by cpuset_mutex (with cpus_read_lock held) or cpus_write_lock. + * Additionally tmigr_available_mutex serialises set/clear operations with= each other. */ static cpumask_var_t tmigr_available_cpumask; +static DEFINE_MUTEX(tmigr_available_mutex); + +/* Enabled during late initcall */ +static DEFINE_STATIC_KEY_FALSE(tmigr_exclude_isolated); =20 #define TMIGR_NONE 0xFF #define BIT_CNT 8 @@ -438,6 +444,33 @@ static inline bool tmigr_is_not_available(struct tmigr= _cpu *tmc) return !(tmc->tmgroup && tmc->available); } =20 +/* + * Returns true if @cpu should be excluded from the hierarchy as isolated. + * Domain isolated CPUs don't participate in timer migration, nohz_full CP= Us + * are still part of the hierarchy but become idle (from a tick and timer + * migration perspective) when they stop their tick. This lets the timekee= ping + * CPU handle their global timers. Marking also isolated CPUs as idle woul= d be + * too costly, hence they are completely excluded from the hierarchy. + * This check is necessary, for instance, to prevent offline isolated CPUs= from + * being incorrectly marked as available once getting back online. + * + * This function returns false during early boot and the isolation logic is + * enabled only after isolated CPUs are marked as unavailable at late boot. + * The tick CPU can be isolated at boot, however we cannot mark it as + * unavailable to avoid having no global migrator for the nohz_full CPUs. = This + * should be ensured by the callers of this function: implicitly from hotp= lug + * callbacs and explicitly in tmigr_init_isolation() and + * tmigr_isolated_exclude_cpumask(). + */ +static inline bool tmigr_is_isolated(int cpu) +{ + if (!static_branch_unlikely(&tmigr_exclude_isolated)) + return false; + return (!housekeeping_cpu(cpu, HK_TYPE_DOMAIN) || + cpuset_cpu_is_isolated(cpu)) && + housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE); +} + /* * Returns true, when @childmask corresponds to the group migrator or when= the * group is not active - so no migrator is set. @@ -1439,8 +1472,12 @@ static int tmigr_clear_cpu_available(unsigned int cp= u) int migrator; u64 firstexp; =20 + guard(mutex)(&tmigr_available_mutex); + cpumask_clear_cpu(cpu, tmigr_available_cpumask); scoped_guard(raw_spinlock_irq, &tmc->lock) { + if (!tmc->available) + return 0; tmc->available =3D false; WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 @@ -1468,8 +1505,15 @@ static int tmigr_set_cpu_available(unsigned int cpu) if (WARN_ON_ONCE(!tmc->tmgroup)) return -EINVAL; =20 + if (tmigr_is_isolated(cpu)) + return 0; + + guard(mutex)(&tmigr_available_mutex); + cpumask_set_cpu(cpu, tmigr_available_cpumask); scoped_guard(raw_spinlock_irq, &tmc->lock) { + if (tmc->available) + return 0; trace_tmigr_cpu_available(tmc); tmc->idle =3D timer_base_is_idle(); if (!tmc->idle) @@ -1479,6 +1523,103 @@ static int tmigr_set_cpu_available(unsigned int cpu) return 0; } =20 +static void tmigr_cpu_isolate(struct work_struct *ignored) +{ + tmigr_clear_cpu_available(smp_processor_id()); +} + +static void tmigr_cpu_unisolate(struct work_struct *ignored) +{ + tmigr_set_cpu_available(smp_processor_id()); +} + +/** + * tmigr_isolated_exclude_cpumask - Exclude given CPUs from hierarchy + * @exclude_cpumask: the cpumask to be excluded from timer migration hiera= rchy + * + * This function can be called from cpuset code to provide the new set of + * isolated CPUs that should be excluded from the hierarchy. + * Online CPUs not present in exclude_cpumask but already excluded are bro= ught + * back to the hierarchy. + * Functions to isolate/unisolate need to be called locally and can sleep. + */ +int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask) +{ + struct work_struct __percpu *works __free(free_percpu) =3D + alloc_percpu(struct work_struct); + cpumask_var_t cpumask __free(free_cpumask_var) =3D CPUMASK_VAR_NULL; + int cpu; + + lockdep_assert_cpus_held(); + + if (!works) + return -ENOMEM; + if (!alloc_cpumask_var(&cpumask, GFP_KERNEL)) + return -ENOMEM; + + /* + * First set previously isolated CPUs as available (unisolate). + * This cpumask contains only CPUs that switched to available now. + */ + cpumask_andnot(cpumask, cpu_online_mask, exclude_cpumask); + cpumask_andnot(cpumask, cpumask, tmigr_available_cpumask); + + for_each_cpu(cpu, cpumask) { + struct work_struct *work =3D per_cpu_ptr(works, cpu); + + INIT_WORK(work, tmigr_cpu_unisolate); + schedule_work_on(cpu, work); + } + for_each_cpu(cpu, cpumask) + flush_work(per_cpu_ptr(works, cpu)); + + /* + * Then clear previously available CPUs (isolate). + * This cpumask contains only CPUs that switched to not available now. + * There cannot be overlap with the newly available ones. + */ + cpumask_and(cpumask, exclude_cpumask, tmigr_available_cpumask); + cpumask_and(cpumask, cpumask, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)); + /* + * Handle this here and not in the cpuset code because exclude_cpumask + * might include also the tick CPU if included in isolcpus. + */ + for_each_cpu(cpu, cpumask) { + if (!tick_nohz_cpu_hotpluggable(cpu)) { + cpumask_clear_cpu(cpu, cpumask); + break; + } + } + + for_each_cpu(cpu, cpumask) { + struct work_struct *work =3D per_cpu_ptr(works, cpu); + + INIT_WORK(work, tmigr_cpu_isolate); + schedule_work_on(cpu, work); + } + for_each_cpu(cpu, cpumask) + flush_work(per_cpu_ptr(works, cpu)); + + return 0; +} + +static int __init tmigr_init_isolation(void) +{ + cpumask_var_t cpumask __free(free_cpumask_var) =3D CPUMASK_VAR_NULL; + + static_branch_enable(&tmigr_exclude_isolated); + + if (!housekeeping_enabled(HK_TYPE_DOMAIN)) + return 0; + if (!alloc_cpumask_var(&cpumask, GFP_KERNEL)) + return -ENOMEM; + + cpumask_andnot(cpumask, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_D= OMAIN)); + + guard(cpus_read_lock)(); + return tmigr_isolated_exclude_cpumask(cpumask); +} + static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, int node) { @@ -1878,3 +2019,4 @@ static int __init tmigr_init(void) return ret; } early_initcall(tmigr_init); +late_initcall(tmigr_init_isolation); --=20 2.51.1