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[147.75.199.223]) by mx.google.com with ESMTPS id z9-20020a05622a060900b004299b7236b8si12963687qta.632.2024.01.31.15.31.42 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 15:31:42 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-47358-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=hjdHutIP; arc=pass (i=1 dkim=pass dkdomain=kernel.org); spf=pass (google.com: domain of linux-kernel+bounces-47358-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) smtp.mailfrom="linux-kernel+bounces-47358-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 3B5FE1C265E4 for ; Wed, 31 Jan 2024 23:31:32 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 816F613AA4E; Wed, 31 Jan 2024 23:12:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hjdHutIP" Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8090E12BF13 for ; Wed, 31 Jan 2024 23:11:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706742718; cv=none; b=BZgXryhWIkkWSkNJ9S8jjRwGdx5VJHTyQYptlslnBtXqQhrOxO16M6GH83oWBQdHgTCVFjbmpqaQYxk7l0nTFqx1I2hl02Dv5uWZYxfPKEQPH6bmxhQkvywEUTBdSuYRE5FZt4fAS1HlPSD3LcU/aZYO0+cUYmyfQoYxB9gVHsM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706742718; c=relaxed/simple; bh=FIezuNO5LWygz4x2wl/CWc53JKa0Be31X2mAyqu+B2I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HfoRPrrvIrJXHBy3deBYBUcic167TcOMibyQLWMabX/AcAhRtr6mO8h4+8YY9Fp6idIgAxmnfn+2TymOJMpYINyugYmHT5ws8gcZm8SSE3O3ATrKDtd1aYLVYJCVBhECcgjGGfZbFVT+ny6yMFbBCf01arneUcQzJm6RZI+UpOU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hjdHutIP; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93D9CC433F1; Wed, 31 Jan 2024 23:11:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706742718; bh=FIezuNO5LWygz4x2wl/CWc53JKa0Be31X2mAyqu+B2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hjdHutIPw6SyPone9MGAdgDQBfK/rFP6rFlD0pFPZLH5dIDU9hsxGP4/HuuepWr1j k9avffTxMdMvlMasC2NF+hmKKjbkp8Ahjm3zLClIzzafqM0hp0kUSTz+4CN4RF7o2X 9hEjIHM08c2XHKe4euz2uC0NsuDl3oDnGOXJH/esUiEMzeMBcqyrKRzWNbl+RBT6ej zSIL19C2Kb0nYkC4FVHlOEiJ9t0bLTK8lLWJViUDMskM69fRWYwOhUTNR4/qb8lvrq bcXp2TAzUB2hniEs2xw/TDm/z+H+hpVmNH6faW0WY0r3/VdZU6wfA6MP8VqpJcahkV lTZYF/l4bVv+Q== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , Anna-Maria Behnsen , Peng Liu , Joel Fernandes Subject: [PATCH 14/15] tick: Shut down low-res tick from dying CPU Date: Thu, 1 Feb 2024 00:11:19 +0100 Message-ID: <20240131231120.12006-15-frederic@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240131231120.12006-1-frederic@kernel.org> References: <20240131231120.12006-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1789650694273157887 X-GMAIL-MSGID: 1789650694273157887 The timekeeping duty is handed over from the outgoing CPU within stop machine. This works well if CONFIG_NO_HZ_COMMON=n or the tick is in high-res mode. However in low-res dynticks mode, the tick isn't cancelled until the clockevent is shut down, which can happen later. The tick may therefore fire again once IRQs are re-enabled on stop machine and until IRQs are disabled for good upon the last call to idle. That's so many opportunities for a timekeeper to go idle and the outgoing CPU to take over that duty. This is why tick_nohz_idle_stop_tick() is called one last time on idle if the CPU is seen offline: so that the timekeeping duty is handed over again in case the CPU has re-taken the duty. This means there are two timekeeping handovers on CPU down hotplug with different undocumented constraints and purposes: 1) A handover on stop machine for !dynticks || highres. All online CPUs are guaranteed to be non-idle and the timekeeping duty can be safely handed-over. The hrtimer tick is cancelled so it is guaranteed that in dynticks mode the outgoing CPU won't take again the duty. 2) A handover on last idle call for dynticks && lowres. Setting the duty to TICK_DO_TIMER_NONE makes sure that a CPU will take over the timekeeping. Prepare for consolidating the handover to a single place (the first one) with shutting down the low-res tick as well from tick_cancel_sched_timer() as well. This will simplify the handover and unify the tick cancellation between high-res and low-res. Reviewed-by: Thomas Gleixner Signed-off-by: Frederic Weisbecker --- kernel/time/tick-common.c | 3 ++- kernel/time/tick-sched.c | 32 +++++++++++++++++++++++++------- kernel/time/tick-sched.h | 4 ++-- 3 files changed, 29 insertions(+), 10 deletions(-) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 522414089c0d..9cd09eea06d6 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -410,7 +410,8 @@ int tick_cpu_dying(unsigned int dying_cpu) if (tick_do_timer_cpu == dying_cpu) tick_do_timer_cpu = cpumask_first(cpu_online_mask); - tick_cancel_sched_timer(dying_cpu); + /* Make sure the CPU won't try to retake the timekeeping duty */ + tick_sched_timer_dying(dying_cpu); /* Remove CPU from timer broadcasting */ tick_offline_cpu(dying_cpu); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 67759e7e025a..cb8e4a171288 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -308,6 +308,14 @@ static enum hrtimer_restart tick_nohz_handler(struct hrtimer *timer) return HRTIMER_RESTART; } +static void tick_sched_timer_cancel(struct tick_sched *ts) +{ + if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) + hrtimer_cancel(&ts->sched_timer); + else if (tick_sched_flag_test(ts, TS_FLAG_NOHZ)) + tick_program_event(KTIME_MAX, 1); +} + #ifdef CONFIG_NO_HZ_FULL cpumask_var_t tick_nohz_full_mask; EXPORT_SYMBOL_GPL(tick_nohz_full_mask); @@ -997,10 +1005,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) * the tick timer. */ if (unlikely(expires == KTIME_MAX)) { - if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) - hrtimer_cancel(&ts->sched_timer); - else - tick_program_event(KTIME_MAX, 1); + tick_sched_timer_cancel(ts); return; } @@ -1560,14 +1565,27 @@ void tick_setup_sched_timer(bool hrtimer) tick_nohz_activate(ts); } -void tick_cancel_sched_timer(int cpu) +/* + * Shut down the tick and make sure the CPU won't try to retake the timekeeping + * duty before disabling IRQs in idle for the last time. + */ +void tick_sched_timer_dying(int cpu) { + struct tick_device *td = &per_cpu(tick_cpu_device, cpu); struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); + struct clock_event_device *dev = td->evtdev; ktime_t idle_sleeptime, iowait_sleeptime; unsigned long idle_calls, idle_sleeps; - if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) - hrtimer_cancel(&ts->sched_timer); + /* This must happen before hrtimers are migrated! */ + tick_sched_timer_cancel(ts); + + /* + * If the clockevents doesn't support CLOCK_EVT_STATE_ONESHOT_STOPPED, + * make sure not to call low-res tick handler. + */ + if (tick_sched_flag_test(ts, TS_FLAG_NOHZ)) + dev->event_handler = clockevents_handle_noop; idle_sleeptime = ts->idle_sleeptime; iowait_sleeptime = ts->iowait_sleeptime; diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h index bbe72a078985..58d8d1c49dd3 100644 --- a/kernel/time/tick-sched.h +++ b/kernel/time/tick-sched.h @@ -106,9 +106,9 @@ extern struct tick_sched *tick_get_tick_sched(int cpu); extern void tick_setup_sched_timer(bool hrtimer); #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS -extern void tick_cancel_sched_timer(int cpu); +extern void tick_sched_timer_dying(int cpu); #else -static inline void tick_cancel_sched_timer(int cpu) { } +static inline void tick_sched_timer_dying(int cpu) { } #endif #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST