From mboxrd@z Thu Jan 1 00:00:00 1970 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 E0501217F53; Wed, 31 Dec 2025 14:02:37 +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=1767189758; cv=none; b=ZEiGfeuF/HOCT+JVYNeMJbFvN70P3/Q5eHOImgqng5qr1MWmUDkcDsBP0f6i4z0t4bldvJym1V7xeD9TDdi+DQKUtfWJ5BKbuIF8Xmc7hBzl7crFvDznID0sd9yxRfci82J6NxMjuveyL14O/S4K3blbYJu/MWYjfnEfPbugveU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767189758; c=relaxed/simple; bh=CBFfLku7dIdIU6H6oIpUvPWYyR6ucYYMUyo6GlFZdAE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=B9OyGoe2LJ+Ze3m/J6cf+4H3/QKBQ+FlbIYRrc0fLjX2TqYmJMFLdcCtcID9tPwibNx4oMXurVE02zFArN0xZh3crzWEd/y2lKR0luZaj17sXb0+ku+W+20v1MAdKnq543jUXAwcwa7/8UccNYO2V2utcYNBY3WGUOF6b5YNPDU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V/KYCPL7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="V/KYCPL7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAA17C113D0; Wed, 31 Dec 2025 14:02:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767189757; bh=CBFfLku7dIdIU6H6oIpUvPWYyR6ucYYMUyo6GlFZdAE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=V/KYCPL7ZtkMijc6GCGy07DqTpJm2bcO1Hyk7oeLdmLDr4cryXHiAbYSa0rdHoTmz xO1R86BMlXOvB7Bi6HCf0I6MrrXlvW4Tifmo/YaGV1r6/hXHdzochqy+Rx9CDugnW8 KL0pY73twndKcZdjNDfVh7l6tZDUjQW4VDWv/nAL9ad6qz6ZAUtNrHXDCfP2Cywtm6 ugYPs4h+jagAwy6hsofbysUt3OS9gH+6R84kJxL4x3DsSiKIXbQvIHr3qZRG6sMKpf M6jkkbfhDqzpVpnYKxH0r6jDyw29DBX9RAwbViO1Y+CIGYDKBMqcVEFznqc1PXd0Hw Qai/24OW/4z9w== Date: Wed, 31 Dec 2025 15:02:34 +0100 From: Frederic Weisbecker To: Jens Axboe Cc: LKML , Michal =?iso-8859-1?Q?Koutn=FD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Chen Ridong , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH 09/33] block: Protect against concurrent isolated cpuset change Message-ID: References: <20251224134520.33231-1-frederic@kernel.org> <20251224134520.33231-10-frederic@kernel.org> <0f65c4fe-8b10-403d-b5b6-ed33fc4eb69c@kernel.dk> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0f65c4fe-8b10-403d-b5b6-ed33fc4eb69c@kernel.dk> Le Mon, Dec 29, 2025 at 05:37:29PM -0700, Jens Axboe a écrit : > On 12/24/25 6:44 AM, Frederic Weisbecker wrote: > > The block subsystem prevents running the workqueue to isolated CPUs, > > including those defined by cpuset isolated partitions. Since > > HK_TYPE_DOMAIN will soon contain both and be subject to runtime > > modifications, synchronize against housekeeping using the relevant lock. > > > > For full support of cpuset changes, the block subsystem may need to > > propagate changes to isolated cpumask through the workqueue in the > > future. > > > > Signed-off-by: Frederic Weisbecker > > --- > > block/blk-mq.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index 1978eef95dca..0037af1216f3 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -4257,12 +4257,16 @@ static void blk_mq_map_swqueue(struct request_queue *q) > > > > /* > > * Rule out isolated CPUs from hctx->cpumask to avoid > > - * running block kworker on isolated CPUs > > + * running block kworker on isolated CPUs. > > + * FIXME: cpuset should propagate further changes to isolated CPUs > > + * here. > > */ > > + rcu_read_lock(); > > for_each_cpu(cpu, hctx->cpumask) { > > if (cpu_is_isolated(cpu)) > > cpumask_clear_cpu(cpu, hctx->cpumask); > > } > > + rcu_read_unlock(); > > Want me to just take this one separately and get it out of your hair? > Doesn't seem to have any dependencies. The patch could be applied alone but the rest of the patchset needs it, otherwise it may dereference freed memory. So I fear it needs to stay within the lot. I appreciate the offer though. But an ack would help, even if I must admit this single patch (which doesn't change current behaviour) leaves a bitter taste because complete handling of cpuset isolated partition change will require more work. Speaking of, is there a way that I missed to define/overwrite the above hctx->cpumask on runtime? Thanks. -- Frederic Weisbecker SUSE Labs