From nobody Sun Oct 5 09:04:16 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 A9C0428A406 for ; Wed, 6 Aug 2025 09:39:16 +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=1754473158; cv=none; b=Y/t5+hYgOxyw2kcE2BoYMW4iK5/1Dr6wfNmBTDjMSndJHcPt28omEe2qRRz4H/8laTBpnLOtpNY3ReZbUsEmHkwy/vyZUW5L4+osavo7gZev/amEl6yzIkyBGHvpajbHdjC4emE27cCB3+PZcji6Qt7p3aHMURoiRxQqW7W0F9M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473158; c=relaxed/simple; bh=dzphjO/XH5mpfwewleznZjBQDK2wTt9cJNxDCg1iR2E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DwSsoSMCftl0OjCXiIO1pl4NAR0bDyJW0OSotE8ED3uWP+SF2eTHzgtFDANUQ8VY3FEh/qIWs2HfReWK3y80VtDVP3xB1ZvQ1Wn49cz4skndvjf5TBdwLq4Q/I1e1yMIntkdfrXIpINCKwDAMMnlRtr62LmHTnHIKnJv9UTHDzg= 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=K9G+LHXp; 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="K9G+LHXp" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473154; 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=2dFmTBAK5e28d1SFufaXHR10WXD/bQd9Cmo3nhugP2Y=; b=K9G+LHXp9e7vfeSCn6YpvyEpIDOV5QemU9WHwiA5aauMX9YYQkctqGnaBxVMxyqfzG0mH0 P5WjjqYYyM3rqLKy/Hi4Nl4Zj+P6mOBIDm41FnEwQe8zcirNMNY2DJZ4VvzJuDRtLxr6rN pqDGjXj+11oi+2ox3iyXGCvun4Ih1Yo= 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-21-wvIf0g3mO--YY-sjZ_o_eA-1; Wed, 06 Aug 2025 05:39:11 -0400 X-MC-Unique: wvIf0g3mO--YY-sjZ_o_eA-1 X-Mimecast-MFC-AGG-ID: wvIf0g3mO--YY-sjZ_o_eA_1754473150 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 008D1195608F; Wed, 6 Aug 2025 09:39:10 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 69BB11800446; Wed, 6 Aug 2025 09:39:07 +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 v10 1/8] timers/migration: Postpone online/offline callbacks registration to late initcall Date: Wed, 6 Aug 2025 11:38:48 +0200 Message-ID: <20250806093855.86469-2-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" From: Frederic Weisbecker During the early boot process, the default clocksource used for timekeeping is the jiffies. Better clocksources can only be selected once clocksource_done_booting() is called as an fs initcall. NOHZ can only be enabled after that stage, making global timer migration irrelevant up to that point. Therefore, don't bother with trashing the cache within that tree from the SMP bootup until NOHZ even matters. Make the CPUs available to the tree on late initcall, after the right clocksource had a chance to be selected. This will also simplify the handling of domain isolated CPUs on further patches. Signed-off-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/time/timer_migration.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index c0c54dc5314c..891891794b92 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -1481,6 +1481,16 @@ static int tmigr_cpu_online(unsigned int cpu) return 0; } =20 +/* + * NOHZ can only be enabled after clocksource_done_booting(). Don't + * bother trashing the cache in the tree before. + */ +static int __init tmigr_late_init(void) +{ + return cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", + tmigr_cpu_online, tmigr_cpu_offline); +} + static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, int node) { @@ -1843,18 +1853,10 @@ static int __init tmigr_init(void) =20 ret =3D cpuhp_setup_state(CPUHP_TMIGR_PREPARE, "tmigr:prepare", tmigr_cpu_prepare, NULL); - if (ret) - goto err; - - ret =3D cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_cpu_online, tmigr_cpu_offline); - if (ret) - goto err; - - return 0; - err: - pr_err("Timer migration setup failed\n"); + if (ret) + pr_err("Timer migration setup failed\n"); return ret; } early_initcall(tmigr_init); +late_initcall(tmigr_late_init); --=20 2.50.1 From nobody Sun Oct 5 09:04:16 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 6C70228A3FA for ; Wed, 6 Aug 2025 09:39:16 +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=1754473158; cv=none; b=Q7lCgyAVFNxkJW/AEq1fcHaqg0UkZMpQ//+wIq4DYixu+dPZpRGArwCaMcKAhAsLkl7hw1HTUqDKs9M13HzxXCynBvTSC4/lhrnEeFljxUchrB8LjtPMTwf9Uy+b0E96pOqXymT3HAps6isV2/iKlH4DOJC4wPt2qQ3Q00S/go4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473158; c=relaxed/simple; bh=2k5yEzfufKgnBRj8JIhZV7ZkaQdISnBdkqCuTW4/Dug=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mw9mMVhF4zWT2pVyMfwMldDo5Wx/5SLWNO5IoZevF3irq61FO7Xa632eKE6CLczr7BXU4GbE9zHsBJXbRBz3myanfauaCV1esuIG9lAS9NqVPnkvDuHDRUrW1mJh5yMca4bb3WM0wVd6ocukKuZRKI1U+OUq0f03s8LffVnHSb0= 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=aGZ07F4x; 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="aGZ07F4x" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473155; 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=WsaM/+IDmZbCwu63ppMgMMObFC3jn1+84pxM4xGsofk=; b=aGZ07F4xzScgX+BDR8bFnvTlc2nGg1XZva53HKQPZtoilAsK7dL/QZeJUZx+t2OeXYlvOH OBd59LkmikKaVlMpSa6XDWGUw3+4ZIQjjKnfoHgLN7+TxnAdbOUxx21lrDMLhus9WrC+cZ HPP3SRO5h3J0TPsXHUT58o7LIRtI2ng= 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-693-zM2aJnduOGuRSh61KQWB1Q-1; Wed, 06 Aug 2025 05:39:14 -0400 X-MC-Unique: zM2aJnduOGuRSh61KQWB1Q-1 X-Mimecast-MFC-AGG-ID: zM2aJnduOGuRSh61KQWB1Q_1754473153 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 118F0180036E; Wed, 6 Aug 2025 09:39:13 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 90B461800280; Wed, 6 Aug 2025 09:39:10 +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 v10 2/8] timers: Rename tmigr 'online' bit to 'available' Date: Wed, 6 Aug 2025 11:38:49 +0200 Message-ID: <20250806093855.86469-3-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 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 Signed-off-by: Gabriele Monaco --- include/trace/events/timer_migration.h | 4 ++-- kernel/time/timer_migration.c | 22 +++++++++++----------- kernel/time/timer_migration.h | 2 +- 3 files changed, 14 insertions(+), 14 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 891891794b92..55b186fd146c 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -427,7 +427,7 @@ 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; } @@ -1432,19 +1432,19 @@ 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 /* @@ -1452,7 +1452,7 @@ 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) { @@ -1463,7 +1463,7 @@ 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 @@ -1472,11 +1472,11 @@ 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; } @@ -1488,7 +1488,7 @@ static int tmigr_cpu_online(unsigned int cpu) static int __init tmigr_late_init(void) { return cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_cpu_online, tmigr_cpu_offline); + tmigr_set_cpu_available, tmigr_clear_cpu_available); } =20 static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, 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; + bool available; bool idle; bool remote; struct tmigr_group *tmgroup; --=20 2.50.1 From nobody Sun Oct 5 09:04:16 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 B5EC628AAF8 for ; Wed, 6 Aug 2025 09:39:21 +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=1754473163; cv=none; b=tEXbM716VeIgdn8kBtbhNmFAvDw4b17+XwjWJQ2o7/bLAtUSRYk7ruUFzEfZ5KPO1i4YwuoMo3DiA/N3DR17UW5v1oRjV0Xnl+nASUB0fcGF71z5Jf0khMroCN+UalDvhgebM6K3cpKHUurMhQvHvC9vFX084gt7ZLQ7d4cv2tc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473163; c=relaxed/simple; bh=8TkkDl9e0kta0uD/LKLHtBK0W5esLyJHiKmFGyDJ5ZQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BgDhYXEJ3K84ZZGXIrVhF18JbP74VhOqFF6fKBioyTWsTSdU7XRCGcj8OigzA70GUg1U7ZnyngirWBRDk89pAmI1/552iow3akYI3SmR1+HA/Bzc8HFD1Gm5ZJ5Rn8mlDk8THtFCeQRlqI+PT360/DXhnsNeXmpvhJKl+sTcyJ8= 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=AgROqMBr; 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="AgROqMBr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473160; 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=Wr2JNjgqP4AgIwwo35G6BEw7VGApArP7udy8G4uczbw=; b=AgROqMBr8v/trj2Rfr6emedy1VTJkDfN47e88c7e6u+9LTNZugwYm83t6SCi9pXpKTc5cv rRvYDN94T5rtUUH2h+ffLQkl/MB+k6sYJLXxHX6/2Pt9Yo4SVp+1JtSUedf39IK3liosHz Xd9mw0kwsm99u6xTV6oSnJc7ih6uHgs= 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-448-h4tu0qXWPiykZZtR6HSK0Q-1; Wed, 06 Aug 2025 05:39:17 -0400 X-MC-Unique: h4tu0qXWPiykZZtR6HSK0Q-1 X-Mimecast-MFC-AGG-ID: h4tu0qXWPiykZZtR6HSK0Q_1754473156 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 549391800446; Wed, 6 Aug 2025 09:39:16 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id BC25F1800446; Wed, 6 Aug 2025 09:39:13 +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 v10 3/8] timers: Add the available mask in timer migration Date: Wed, 6 Aug 2025 11:38:50 +0200 Message-ID: <20250806093855.86469-4-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 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 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 55b186fd146c..865071ab5062 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -422,6 +422,12 @@ static unsigned int tmigr_crossnode_level __read_mostl= y; =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 @@ -1443,6 +1449,7 @@ 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); @@ -1456,7 +1463,7 @@ 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 @@ -1471,6 +1478,7 @@ 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(); @@ -1808,6 +1816,11 @@ 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 2.50.1 From nobody Sun Oct 5 09:04:16 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 F2C2728A1E6 for ; Wed, 6 Aug 2025 09:39:24 +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=1754473166; cv=none; b=Em93K9/qgPoLEQ4EkGq31VPGyDKFPqA+O62h2812pxy7fEh4Mo7JA+YRj0vfHopQ2UYPuluIQQX0UjoeihMvZB/+SxdIQx2BZkMaO3ADbRzDtkYSFTO24hbh545IFA9ZtLgRfyWThSa2HslIbPskcCp2JBxkUtunN2BUVCvroLg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473166; c=relaxed/simple; bh=MiSGVhpIQjlXN9JkbotVzlfVE6k2035BwVIFbacwRoU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FFjMVDUZtN8FyVgQB68HVMGFDWWcBmoTauAns0sw6ihzuMDzyRq9Pc36/I/aff81oefBWPnizX5pVB/Cs2bH8bLPjZF+2RGVkAu1fdEaQqIgSvWs1pXBzd1u/8AowXRK5buvr+MFM+vQwgPisxsKJ9+24o8hUufKO5Fv09k8w1g= 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=YKTAAhR4; 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="YKTAAhR4" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473163; 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=teCf0CHCppIIE/YdmrDxUHZ2E2wZCqLiu68DZNCBVsI=; b=YKTAAhR4CAK2eSlQcm6SXBgpIngNCnQluIXffy3Zo0JYsBb3OFbru+nQGzLo4ARJgl4Hnb crcKnMwqmdQNBpbhUe8hJmdbMepDcc0o7cCf+kO1UPd9hV8wK6yQsaEt3E+Kgl5wQRN4KV 7bHsrZJe6Zl1SKjPg8iD0Pk7Ix0nWUw= Received: from mx-prod-mc-03.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-441-KJAH6uKYPkCeHPKYTQ2Xrg-1; Wed, 06 Aug 2025 05:39:20 -0400 X-MC-Unique: KJAH6uKYPkCeHPKYTQ2Xrg-1 X-Mimecast-MFC-AGG-ID: KJAH6uKYPkCeHPKYTQ2Xrg_1754473159 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 94D2619560AA; Wed, 6 Aug 2025 09:39:19 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0AA981800446; Wed, 6 Aug 2025 09:39:16 +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 v10 4/8] timers: Use scoped_guard when setting/clearing the tmigr available flag Date: Wed, 6 Aug 2025 11:38:51 +0200 Message-ID: <20250806093855.86469-5-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 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 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 865071ab5062..0a3a26e766d0 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -1450,17 +1450,17 @@ 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); @@ -1479,13 +1479,13 @@ 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 2.50.1 From nobody Sun Oct 5 09:04:16 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 3BA6E28B41A for ; Wed, 6 Aug 2025 09:39:28 +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=1754473169; cv=none; b=aWWAxWNaJcZyRyyj3EZzgCQVb3CRz/utF9FFYhgZO5E4vae3AVPyNiDL/xxEOVUp2aXco0ORbJ/4MS1GmttPbt2NBf/LiHOYAkdWP44vQLgv0DUJRTknmNvUIe5KpQAbluS4yyTtMJWigbpIn0NDpdXUEFng3558UKLstZ4nKzo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473169; c=relaxed/simple; bh=KRV1uXGYcZHkF1428JaQE47itvL659ZCiDzud4k4Es8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uAEhFuWYis/gYvAxsBHvX2DM+2r8BCYn+vEZ6AuCEH/w/PNZDuAFHJprKBPM9yYtiKvV1v388knPf3esdx28/BdlmLQQFTcj44vxir+aBVHUn7RoUgfyEbAVwiblWiyS6lmKPiI98lzNxtHYnVzIxVMWHqg3n2ubbjqsD216hYo= 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=XsFNUCjg; 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="XsFNUCjg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473167; 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=OVLkMLH39nJ6vOhn8AQhGRkWMGBi+XodCwJjcIzIfGw=; b=XsFNUCjgsyIXA1a/G647oc4ywjoBTQ4FXq5eVQf2q1X/+EBlywyqlHBDWXdQ33zqQ6oec9 gL3NvSRH2r4GrD65bpNO0jX9CmedZGkDJ/ImAVistkcXaKex5X04bvlfOdcZUMyBw81x+O 3o97Jt/XWe0i2YjHaTa+XIUAC8Bu7g8= 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-387-GgmSuImFN9e1ZvCb7ulr0w-1; Wed, 06 Aug 2025 05:39:24 -0400 X-MC-Unique: GgmSuImFN9e1ZvCb7ulr0w-1 X-Mimecast-MFC-AGG-ID: GgmSuImFN9e1ZvCb7ulr0w_1754473163 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 14FC21800357; Wed, 6 Aug 2025 09:39:23 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4AD641800280; Wed, 6 Aug 2025 09:39:19 +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 v10 5/8] cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_exclusion_cpumasks() Date: Wed, 6 Aug 2025 11:38:52 +0200 Message-ID: <20250806093855.86469-6-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 Content-Type: text/plain; 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_exclusion_cpumasks() to prepare for other functions unrelated to workqueues to be called in that spot. Acked-by: Frederic Weisbecker Acked-by: Waiman Long Signed-off-by: Gabriele Monaco --- 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 3bc4301466f3..6e3f44ffaa21 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_exclusion_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_exclusion_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_exclusion_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_exclusion_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_exclusion_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_exclusion_cpumasks(isolcpus_updated); =20 /* Force update if switching back to member & update effective_xcpus */ update_cpumasks_hier(cs, &tmpmask, !new_prs); --=20 2.50.1 From nobody Sun Oct 5 09:04:16 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 CFC6F28B7C2 for ; Wed, 6 Aug 2025 09:39:32 +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=1754473174; cv=none; b=j3GqFdvmWHaHeObaYHztDHL2YL7BLV7culVOcVARHUaKTuFfq020Ypb7d0S5wkBZPHyr5Yscph/zFdI4h4h1iTtx2P5ROxjsYanRva5u+64Sur+XCwvnrpQQt2DqW1zolJ66OPFA3jk5OMVMCozARYBGQyjlc7DQ94g65UrW/OI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473174; c=relaxed/simple; bh=h8XNOggJ4J79JZ6BAnaBb7IQ4FdUTQtcb4Y9fTXyj+M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=prINFqCq8+kP1eRcCfUzCBnK/m0kXO6Brq0yQEudcFzWznC3tcDxGNrcb7Ua6DYk1TF9VSXhRlrm5VnhnkCTxzCQ6Mv18Bgxepe9TR43e++SuxxV/+ZXA6DN6mgSnvYB30VMdDE+gwZxme2h9XlyCYnhPwPn+9bUqGJYrbYzUJ8= 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=OQX9ISRL; 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="OQX9ISRL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473171; 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=g/iy7OCh32FBZCNmBHQsT+SwnOX4MJIRF8yuLtEQGIc=; b=OQX9ISRLLds23FbaaBDcvaEkYZvYtT+O7Tw1iZj4WBUw89f8MMCgYSSslTLcmFNQvW5l0+ pqichj97DbK+uq0jx1PHwYQa458UI9q2mLL39a0qLUVAtz7buQ0e3gE0enqLyJgTFZooGq LFHAn9wPOFyzS0zoOdNZt8+KslM+7o4= 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-498-_J_7cYq0N_ayUCpTlgbCdQ-1; Wed, 06 Aug 2025 05:39:28 -0400 X-MC-Unique: _J_7cYq0N_ayUCpTlgbCdQ-1 X-Mimecast-MFC-AGG-ID: _J_7cYq0N_ayUCpTlgbCdQ_1754473167 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 62BC81800293; Wed, 6 Aug 2025 09:39:27 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id C57D91800280; Wed, 6 Aug 2025 09:39:23 +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 v10 6/8] sched/isolation: Force housekeeping if isolcpus and nohz_full don't leave any Date: Wed, 6 Aug 2025 11:38:53 +0200 Message-ID: <20250806093855.86469-7-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 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. 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..0bf7b91684c0 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 nr_cpu_ids || first_cpu >=3D 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 2.50.1 From nobody Sun Oct 5 09:04:16 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 9EAD528B7DD for ; Wed, 6 Aug 2025 09:39:35 +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=1754473177; cv=none; b=Imkjkcw635QySdNDBjdcHPkHxAYjYesVQwCeBf5enau1GC2oijFLDxvgld0BWsY03EWCE9UkwBhMuBUXZindoWQa3KAn3LFpMuxK/iA88FdklhfJ0K26gx67qked54JaPYYiVj28c/zWap5Tfjs0UVJ6u2kCG9a5rY7nWkiF7IU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473177; c=relaxed/simple; bh=CRY0+GnaBWrlfpe8iXJlxsyVpbGWBfiDOGycoYwQiYk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=a11nn8mOpYT5ahmAufuWnH5TCQdAT4D98PumUR5gtOCQS0J9fAKvDqqf/kKlqWGHfeociF/3C48GxGb3uxElaxYIZm5JL6Vxx4FbMWoBlfNbS/+0UQieCdKWAkeGRaf48bRXNlKl6UazjrwP11rpGLEUxoO+Mg539MiILBV/Es8= 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=CJlSE2U3; 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="CJlSE2U3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473174; 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=c/4Yb/ZEMmy5bdm/K/cc0fxTqmOnDgZxgOXUTfhox3U=; b=CJlSE2U3vGkmukmwPBuylysx7YPAgvTxZVpXpzNLPyG958a+QTWL/kZvikOMTcymvg5VhW 3zfR837gm7pPTSM8crOzjW6afYFxAXYBNq4RsP4Ow5gxz+ykAMyp0Mfbqk2ck54El+NBAn m8tWQ41N98PYEvw7uPsD3epMd/WpD+Q= 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-256-wZvVtGD7PkSwOCI_G3HWHg-1; Wed, 06 Aug 2025 05:39:31 -0400 X-MC-Unique: wZvVtGD7PkSwOCI_G3HWHg-1 X-Mimecast-MFC-AGG-ID: wZvVtGD7PkSwOCI_G3HWHg_1754473170 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 63D14180036F; Wed, 6 Aug 2025 09:39:30 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 010C11800446; Wed, 6 Aug 2025 09:39:27 +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 v10 7/8] cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping Date: Wed, 6 Aug 2025 11:38:54 +0200 Message-ID: <20250806093855.86469-8-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" Currently the user can set up isolated cpus via cpuset 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 blocking any assignation that would cause the union of domain isolated cpus and nohz_full to covers all CPUs. Acked-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/cgroup/cpuset.c | 57 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 6e3f44ffaa21..7b66ccedbc53 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1275,6 +1275,19 @@ static void isolated_cpus_update(int old_prs, int ne= w_prs, struct cpumask *xcpus cpumask_andnot(isolated_cpus, isolated_cpus, xcpus); } =20 +/* + * isolated_cpus_should_update - Returns if the isolated_cpus mask needs u= pdate + * @prs: new or old partition_root_state + * @parent: parent cpuset + * Return: true if isolated_cpus needs modification, false otherwise + */ +static bool isolated_cpus_should_update(int prs, struct cpuset *parent) +{ + if (!parent) + parent =3D &top_cpuset; + return prs !=3D parent->partition_root_state; +} + /* * partition_xcpus_add - Add new exclusive CPUs to partition * @new_prs: new partition_root_state @@ -1339,6 +1352,36 @@ static bool partition_xcpus_del(int old_prs, struct = cpuset *parent, return isolcpus_updated; } =20 +/* + * isolcpus_nohz_conflict - check for isolated & nohz_full conflicts + * @new_cpus: cpu mask for cpus that are going to be isolated + * Return: true if there is conflict, false otherwise + * + * If nohz_full is enabled and we have isolated CPUs, their combination mu= st + * still leave housekeeping CPUs. + */ +static bool isolcpus_nohz_conflict(struct cpumask *new_cpus) +{ + cpumask_var_t full_hk_cpus; + int res =3D false; + + if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE)) + return false; + + if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL)) + return true; + + cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE), + housekeeping_cpumask(HK_TYPE_DOMAIN)); + cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus); + cpumask_and(full_hk_cpus, full_hk_cpus, cpu_online_mask); + if (!cpumask_weight_andnot(full_hk_cpus, new_cpus)) + res =3D true; + + free_cpumask_var(full_hk_cpus); + return res; +} + static void update_exclusion_cpumasks(bool isolcpus_updated) { int ret; @@ -1464,6 +1507,9 @@ static int remote_partition_enable(struct cpuset *cs,= int new_prs, if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) || cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus)) return PERR_INVCPUS; + if (isolated_cpus_should_update(new_prs, NULL) && + isolcpus_nohz_conflict(tmp->new_cpus)) + return PERR_HKEEPING; =20 spin_lock_irq(&callback_lock); isolcpus_updated =3D partition_xcpus_add(new_prs, NULL, tmp->new_cpus); @@ -1563,6 +1609,9 @@ static void remote_cpus_update(struct cpuset *cs, str= uct cpumask *xcpus, else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) || cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)) cs->prs_err =3D PERR_NOCPUS; + else if (isolated_cpus_should_update(prs, NULL) && + isolcpus_nohz_conflict(tmp->addmask)) + cs->prs_err =3D PERR_HKEEPING; if (cs->prs_err) goto invalidate; } @@ -1914,6 +1963,12 @@ static int update_parent_effective_cpumask(struct cp= uset *cs, int cmd, return err; } =20 + if (deleting && isolated_cpus_should_update(new_prs, parent) && + isolcpus_nohz_conflict(tmp->delmask)) { + cs->prs_err =3D PERR_HKEEPING; + return PERR_HKEEPING; + } + /* * Change the parent's effective_cpus & effective_xcpus (top cpuset * only). @@ -2934,6 +2989,8 @@ static int update_prstate(struct cpuset *cs, int new_= prs) * Need to update isolated_cpus. */ isolcpus_updated =3D true; + if (isolcpus_nohz_conflict(cs->effective_xcpus)) + err =3D PERR_HKEEPING; } else { /* * Switching back to member is always allowed even if it --=20 2.50.1 From nobody Sun Oct 5 09:04:16 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 2D58228BA82 for ; Wed, 6 Aug 2025 09:39:38 +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=1754473181; cv=none; b=T8f2ZbDBYc/U8tuheAjnkYbNiA4I2DJ5uDH+L4EtuBQs9hz3taTWvLkfmx96y17qPqAJxGfjVVkac+AifTYPUPQaJAJgFuOQKFlNYHRNA6fjSJhQViXRxLMlPdbo0kJTrqwRd+kkfeBRuG/NuxNeH2w7vGsOHIiuO9AmgYJT6Zc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754473181; c=relaxed/simple; bh=UzBNdo4FDG4Lh7CLufC8kGIXdpIhNvgOn/Gby+8QYKA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Wp7VZxboVH8unZOm8tKH/a1adwtLSNXsIaS03wYvSEKCaOvYX8o0SacMVSr3GKj51PQi8TRKeUfZO1xftfTaeFi+FvJsfWOjgT6k/fD8eCQHPgQC3rohshW4HEYa6N5z8VjtDbBnYSmkbRzO3skiIItT7XGwWPlIZKFknPR2lj8= 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=i1WYP6Pr; 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="i1WYP6Pr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754473177; 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=HdZmIV1NVzMkNRzteqwWlk5HlODlr8/rl1lI0EToPeg=; b=i1WYP6PrUeevhGXOHVXcDHq1FlHJFNzLFHbdUfPzHQSEURY4F7jbD41m53MdD2ET7X+0wC 6Td2vWbhKILpCVAyoKHiRO9/JFzrpepvahdxwA7LALc9KWyldEsG2/mcs9pEspeylTAKnj 1AXYCNenzw5H1ZXov5DcjJ0Tlf1sWs0= Received: from mx-prod-mc-01.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-480-mc0z8U9rNruFgoN6_3638A-1; Wed, 06 Aug 2025 05:39:34 -0400 X-MC-Unique: mc0z8U9rNruFgoN6_3638A-1 X-Mimecast-MFC-AGG-ID: mc0z8U9rNruFgoN6_3638A_1754473173 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 877AC195608E; Wed, 6 Aug 2025 09:39:33 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.45.224.173]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 120281800446; Wed, 6 Aug 2025 09:39:30 +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 v10 8/8] timers: Exclude isolated cpus from timer migration Date: Wed, 6 Aug 2025 11:38:55 +0200 Message-ID: <20250806093855.86469-9-gmonaco@redhat.com> In-Reply-To: <20250806093855.86469-1-gmonaco@redhat.com> References: <20250806093855.86469-1-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 3.4.1 on 10.30.177.111 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) Signed-off-by: Gabriele Monaco --- include/linux/timer.h | 9 +++ kernel/cgroup/cpuset.c | 3 + kernel/time/timer_migration.c | 103 +++++++++++++++++++++++++++++++++- 3 files changed, 112 insertions(+), 3 deletions(-) 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 7b66ccedbc53..2e73fc450a81 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1393,6 +1393,9 @@ static void update_exclusion_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 0a3a26e766d0..07b63be18f83 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" @@ -436,6 +437,23 @@ 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. + */ +static inline bool tmigr_is_isolated(int cpu) +{ + 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. @@ -1451,6 +1469,8 @@ static int tmigr_clear_cpu_available(unsigned int cpu) =20 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 @@ -1470,7 +1490,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu) return 0; } =20 -static int tmigr_set_cpu_available(unsigned int cpu) +static inline int _tmigr_set_cpu_available(unsigned int cpu) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); =20 @@ -1480,6 +1500,8 @@ static int tmigr_set_cpu_available(unsigned int cpu) =20 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) @@ -1489,14 +1511,89 @@ static int tmigr_set_cpu_available(unsigned int cpu) return 0; } =20 +static int tmigr_set_cpu_available(unsigned int cpu) +{ + if (tmigr_is_isolated(cpu)) + return 0; + return _tmigr_set_cpu_available(cpu); +} + +static bool tmigr_should_isolate_cpu(int cpu, void *ignored) +{ + /* + * The tick CPU can be marked as isolated by the cpuset code, however + * we cannot mark it as unavailable to avoid having no global migrator + * for the nohz_full CPUs. + */ + return tick_nohz_cpu_hotpluggable(cpu); +} + +static void tmigr_cpu_isolate(void *ignored) +{ + tmigr_clear_cpu_available(smp_processor_id()); +} + +static void tmigr_cpu_unisolate(void *ignored) +{ + tmigr_set_cpu_available(smp_processor_id()); +} + +static void tmigr_cpu_unisolate_force(void *ignored) +{ + /* + * Required at boot to restore the tick CPU if nohz_full is available. + * Hotplug handlers don't check for tick CPUs during runtime. + */ + _tmigr_set_cpu_available(smp_processor_id()); +} + +int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask) +{ + cpumask_var_t cpumask; + + lockdep_assert_cpus_held(); + + if (!alloc_cpumask_var(&cpumask, GFP_KERNEL)) + return -ENOMEM; + + cpumask_and(cpumask, exclude_cpumask, tmigr_available_cpumask); + cpumask_and(cpumask, cpumask, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)); + on_each_cpu_cond_mask(tmigr_should_isolate_cpu, tmigr_cpu_isolate, NULL, + 1, cpumask); + + cpumask_andnot(cpumask, cpu_online_mask, exclude_cpumask); + cpumask_andnot(cpumask, cpumask, tmigr_available_cpumask); + on_each_cpu_mask(cpumask, tmigr_cpu_unisolate, NULL, 1); + + free_cpumask_var(cpumask); + return 0; +} + /* * NOHZ can only be enabled after clocksource_done_booting(). Don't * bother trashing the cache in the tree before. */ static int __init tmigr_late_init(void) { - return cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_set_cpu_available, tmigr_clear_cpu_available); + int cpu, ret; + + ret =3D cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", + tmigr_set_cpu_available, tmigr_clear_cpu_available); + if (ret) + return ret; + /* + * The tick CPU may not be marked as available in the above call, this + * can occur only at boot as hotplug handlers are not called on the + * tick CPU. Force it enabled here. + */ + for_each_possible_cpu(cpu) { + if (!tick_nohz_cpu_hotpluggable(cpu)) { + ret =3D smp_call_function_single( + cpu, tmigr_cpu_unisolate_force, NULL, 1); + break; + } + } + return ret; } =20 static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, --=20 2.50.1