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 C73AA4F96BE; Mon, 19 Oct 2026 13:09:45 +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=1792415386; cv=none; b=cE213l0inrAYsu/AKyPVQjmmMtUlX5YYqeEVecb+1HA2W3FpG2bEYRJBruS5kDYTMg362bNPQQYg7Mp1cRfdDZ8IYIxuK+8v+ChRHZSVn69X76Xs6xq/p2cNCLvRDA1WUQNUPdR4Yq8s+2Zr3ZhK7Wc6cgfEvwA1PCVl8ceTbHU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792415386; c=relaxed/simple; bh=w1BrRRipaOkIbZu4fuKp4PSlvBlYXbfQrZNXQhM/Y2U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OH/DFDk01dmulbXSCzMxHuzxj91GA5oMnpjHd0XX+eZYKkPfIvlQ1HUB7x9aNmQTpVQS3pOHmwF8+jD82uYANUk53GVj2+Or/oruZe6Y3kAY5/N6D84p53a7zjUfCScAY9g0cZ0NxSOfNdcYoPAxCgfy3igqBVCa9eyt95pCEN0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n0L9xKH2; 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="n0L9xKH2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CB851F000C4; Mon, 19 Oct 2026 13:09:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792415385; bh=ehQznJ1A7d3/2oa5IlIxaIerl/qML7ZXU0JTRcCKZcc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=n0L9xKH2wgCvow6XotvkYeWctkk34LTYqAe//09SuPdqWBLgtYJC3QvzmnQx05Z1B mNOw8GJFlNDxvGj/gb49OKlnQjx0iedidMGGX6tchlBi/ayD+NZ7ATLihhm1De0Sii AEhqI8WQH0fjaziDwKUqdDvLfIlnuQLPp102dLUsP6ayyMx37joykKtNGA/UDp7K9R p7tm3TwH4HmimRjJuxTzSF/l0l8fk0rBGvm8CiFBih96vJ9h8SKhSuIrTzyjvdRjJb 5fCNFtmCNvaTy5fU6OFVq0fBzQ+pNYDAQyK9Y+4EphqaId1c3Iomuj4s5I7vGGMpBQ sVeXRhvyvCgEw== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , "H. Peter Anvin" , Adrian Hunter , Alexander Shishkin , Arnaldo Carvalho de Melo , Borislav Petkov , Dave Hansen , Ian Rogers , Ingo Molnar , James Clark , Jiri Olsa , Marco Crivellari , Mark Rutland , Namhyung Kim , Peter Zijlstra , Phil Auld , Thomas Gleixner , Waiman Long , linux-perf-users@vger.kernel.org, x86@kernel.org Subject: [RFC PATCH 14/49] perf/x86: Move CPUHP_AP_PERF_X86_STARTING post stop_machine() Date: Mon, 19 Oct 2026 15:08:21 +0200 Message-ID: <20261019130856.49711-15-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-perf-users@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(). Here only intel has a dying callback (intel_pmu_cpu_dying()) which does: * Deallocate the per CPU DS structure on the MSR_IA32_DS_AREA. This is already racy against offlining CPUs because all possible CPUs's MSR are written on a hardware event initialization, which still can happen before the CPU actually goes off. * Deallocate PEBS buffer. This is already well synchronized against hotplug up callback. Therefore the related teardwown callback can run concurrently with other CPUs. Move it to post stop_machine() accordingly. Signed-off-by: Frederic Weisbecker --- kernel/cpu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 5ac2a925f7d6..c37fa1272d57 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_PERF_X86_AMD_UNCORE_STARTING); + enum cpuhp_state target = max((int)st->target, CPUHP_AP_PERF_X86_STARTING); int err, cpu = smp_processor_id(); /* Ensure this CPU doesn't handle any more interrupts. */ @@ -1303,7 +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_PERF_X86_AMD_UNCORE_STARTING); + WARN_ON(st->state != CPUHP_AP_PERF_X86_STARTING); /* * Invoke the former CPU_DYING callbacks. DYING must not fail! */ -- 2.53.0