From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CC04833E347 for ; Mon, 19 Oct 2026 13:09:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792415354; cv=none; b=rQBYzH+mgfTrfrCwcTkCWbWaJH9bQAknoWRVWYjcPWw31ztFT7GKPEHRMax04yVmUCXSgnL706SbbhV43tZLHqshTpiUp70lHefugSIIBavLEnAexJSIRjFK6fUSNUPBm09tppm1/SrGfICxNzEtkKtJItl27zqX/803TefqXeY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792415354; c=relaxed/simple; bh=R3iO0YBeO+1YLVtVxqieQpMSgmFrD9t366A6pTmbVY4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lqlo1l7FUoCkudxU/Q2ke2JihZIPcNSAoHdcPY5E+vXusN2gx39G+WwAeKYjdaekzDypcgiTUSur98wyDZzQ4fYBwRuySNv9XHZDEKUL3t4QaZuf8u8ohfyiarr4wJOLXAvQ+7ZQQGBxrEADX/AKaxjRQaP0R0+Tu8lHclcJF9E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nGwqCAcy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nGwqCAcy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F418E1F000C5; Mon, 19 Oct 2026 13:09:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792415352; bh=8nPvTyyxaOr4cFb+Dot9Pu38m3w5s43XoED5ZCnAm0o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nGwqCAcyBNhS34gjpubGAgioulyw0auaSVDK1GK8g1m9+tHa9aPBMwQz5zh5wC6Dg OslyBdEekjA1djj3HNvZAQsRsJen1S7xBPRftAaNPpW4knWjOcMJ1HTtHnF+ikP7Gf 1BTb0JFXm6sv3wAJpfuRouAJFbqbwe3WhUzO3c2rYbd6XvnErqUsiwVPLeHvS9PptH eXu2f3P/cgoyx4bgX8to82LT9ygYDnUvtJ+/Laa0jwpT/6elXFRC43DT9PudlgGMOO cChJm+yceBqZI1iubY2l4f1zrL+S2iqLF97y33FCztBoHzaWs/5N6Kf0rvweQlfGTL bfsGgykc863VA== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Ben Segall , Dietmar Eggemann , Ingo Molnar , Juri Lelli , K Prateek Nayak , Marco Crivellari , Mel Gorman , Peter Zijlstra , Phil Auld , Steven Rostedt , Thomas Gleixner , Valentin Schneider , Vincent Guittot , Waiman Long Subject: [RFC PATCH 03/49] sched: Move CPUHP_AP_SCHED_STARTING to post stop_machine() Date: Mon, 19 Oct 2026 15:08:10 +0200 Message-ID: <20261019130856.49711-4-frederic@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261019130856.49711-1-frederic@kernel.org> References: <20261019130856.49711-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Between CPUHP_TEARDOWN_CPU and CPUHP_AP_OFFLINE, stop_machine executes all the teardown callbacks while stopping all CPUs in the system. This doesn't mix-up well with running RT or isolated tasks. In order to transition smoothly from global stop_machine to finer grained synchronization between teardown callbacks and the other CPUs, a new stop machine post function has been introduced to be executed after the main one with IRQs still disabled while other CPUs can exit stop_machine(). - The nohz_full remote tick can be shutdown safely while it runs concurrently. - Updating the RQ clock shouldn't be a problem while offline with other CPUs around. - Since it is seen offline, no task can be queued to it remotely. - dl server stop is sychronized with rq lock. hrtimer_try_to_cancel() can become racy but then if it fires, it will just early return. - calc_load_migrate() just folds local load to the global accumulation - update_max_interval() only depends on the number of online CPUs, which is stable at this stage. - hrtick_clear() deals with a strictly local timer - sched_core_cpu_dying() doesn't race with anything Move this teardown callback to post stop_machine() accordingly. Signed-off-by: Frederic Weisbecker --- kernel/cpu.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index da07c804ff53..4f3f0ae36893 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1275,7 +1275,7 @@ void clear_tasks_mm_cpumask(int cpu) static int take_cpu_down(void *_param) { struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); - enum cpuhp_state target = max((int)st->target, CPUHP_AP_CACHECTRL_STARTING); + enum cpuhp_state target = max((int)st->target, CPUHP_AP_SCHED_STARTING); int err, cpu = smp_processor_id(); /* Ensure this CPU doesn't handle any more interrupts. */ @@ -1303,8 +1303,7 @@ static int take_cpu_down_post(void *_param) enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE); int cpu = smp_processor_id(); - WARN_ON(st->state != CPUHP_AP_CACHECTRL_STARTING); - + WARN_ON(st->state != CPUHP_AP_SCHED_STARTING); /* * Invoke the former CPU_DYING callbacks. DYING must not fail! */ -- 2.53.0