From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 4214A47B432 for ; Fri, 5 Jun 2026 07:35:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780644926; cv=none; b=ldGcUpBYeAXNZRf2cqyos4G9ObHU3xm+dFYXqEfFwiFfEGoQwjHRmX3ZIUr1kva5C8GubL/ju/wm+/Ls7aSDhf106umBdB6CK2pJy8RDrNuWVmN9iZCUKj3qlOskvgSO1oC/Vk9CvOykYuH0iaP3MhWDlG6TUgG/3EZEMTBkikc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780644926; c=relaxed/simple; bh=YrTuSOVKhy+0zjIegpHr49FpMVaxvAWEkXD+5SPJea8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PtQaR0XFUCBvkISN1Q1p1DpSlOFKH7OMDSF9z46B2UCW3ZA21gq0BciGAhOLcBdwJQFelRoAoppmkw+VQ8l9fZ6HyKpFvGNb/54LyDRwdnoz+9hX57ZSBnz/JF8+0DKTtNmKY1fkocc82oY3o+vQAYXmAn96HLmxyjoJV8Ha00g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=GhO6YyKO; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="GhO6YyKO" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780644912; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=V/38TPRJSdaRiKmREGJMFYleBrRqrj4e5ZZcuBKWtdU=; b=GhO6YyKOZevwWrJCbmMTJVPXvT2bA3Eav/vhGW3N+R7zSw7ra1PUcaT/ow1XGmk/dJGviU 2aqHO5CFFh5iubtoH0haZykLo2BiOLNVEUfhcGVhYinZ399bFRNV0/GWwNug3ImS6Aai2Y +B9I2NHXfW0P7vPYnHPCjREZ7ZYOSM0= Date: Fri, 5 Jun 2026 15:35:01 +0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] cgroup/cpuset: Support multiple source/destination cpusets using pids pattern To: Waiman Long Cc: cgroups@vger.kernel.org, Tejun Heo , Johannes Weiner , linux-kernel@vger.kernel.org References: <20260602023203.248077-7-longman@redhat.com> <20260603102604.177503-1-ridong.chen@linux.dev> <07bfe9cc-b8ab-4c4c-bfe0-b974abd3ff08@redhat.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ridong Chen In-Reply-To: <07bfe9cc-b8ab-4c4c-bfe0-b974abd3ff08@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 6/4/2026 2:47 AM, Waiman Long wrote: > On 6/3/26 6:26 AM, Ridong Chen wrote: >> The current cpuset_can_attach() and cpuset_attach() functions assume task >> migration is from one source cpuset to one destination cpuset. This >> can be >> wrong in several scenarios: >>   - Moving a multi-threaded process with threads in different cpusets >>   - Disabling the cpuset controller (many children to one parent) >>   - Enabling the cpuset controller (one parent to many children) >> >> Fix this by adopting the pids subsystem's per-task accounting pattern. >> In cpuset_can_attach(), use task_cs(task) to get the correct source >> cpuset >> for each task (like pids_can_attach uses task_css), adjust >> nr_deadline_tasks >> and reserve DL bandwidth per-task, and increment attach_in_progress >> per-task >> on the destination cpuset. In cpuset_attach(), handle destination cpuset >> changes within the task iteration loop. >> >> A shared helper cpuset_undo_attach() reverses the per-task operations for >> both partial rollback in cpuset_can_attach() and full reversal in >> cpuset_cancel_attach(). >> >> When multiple source cpusets are detected in can_attach(), set >> attach_many_sources so that cpuset_attach() forces cpus_updated and >> mems_updated to true, ensuring all tasks get properly updated regardless >> of which source cpuset cpuset_attach_old_cs points to. >> >> This eliminates the need for nr_migrate_dl_tasks, sum_migrate_dl_bw, and >> dl_bw_cpu fields in struct cpuset. >> >> Fixes: 4ec22e9c5a90 ("cpuset: Enable cpuset controller in default >> hierarchy") >> Signed-off-by: Ridong Chen > > It is not a problem doing per-task DL BW allocation and eliminating the > *dl_bw* fields. However, updating nr_deadline_tasks before it is > committed can be problematic. > Good to hear that. > nr_deadline_tasks is used in dl_rebuild_rd_accounting() which is called > by partition_sched_domains_locked(). After the release of cpuset_mutex > at the end of cpuset_can_attach() and before cpuset_attach() or > cpuset_cancel_attach() is called, it is possible > that partition_sched_domains_locked() can be called > and dl_rebuild_rd_accounting() is not getting the right DL BW accounting > information. So unless there is a way to confirm that this situation > cannot happen, we can't change nr_deadline_tasks before the attach is > commited. > We can keep the nr_migrate_dl_tasks field and update nr_deadline_tasks once migration is complete. I think this will be much simpler than fixing the issue using lists. -- Best regards, Ridong