From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 71D503148AC for ; Wed, 29 Oct 2025 21:56:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761774995; cv=none; b=iftTsQCDmvdxBz2LgheQgibj1eoESz+7niQ2VYtwWY+wt8YngOijlaU3KLLh/WNDG5d34gOmkGytyhFAjGLw4rgQ9WT8Vb+li5/kHi+u1dvh725RMRrajIFxuTwoJlRe2ucyoOkU0VZ5cMv+yfdgGLUT7AgxdsRu8HkvgXPS9kI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761774995; c=relaxed/simple; bh=YG+OCyXAx1DocZpNMS6gi5m+fDdTlk1ofhG87v5IIig=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rJWr37qhkSky/zfwq+tPBaFMOdynPG1fL08mS38qj8xgtfjhH+gk9moP+5kWQIfmKWDhU7u4uUFyV6wk7YArUG8l6B8pfjKro5SRle7mvMDo5jMjglsN00/omGad9F2GK7/gUQwiPq17Jcl54zfTChWlBJ9feXqhcUSzPnBouSU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=h5l5trJE; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="h5l5trJE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761774992; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=INsiWkY7BmAeJ2Lt+5y778Nm9jHs2zNAVbEZhuTQT9Y=; b=h5l5trJEu+dnihq3yChWxpPKRBSP2ak94yjE41CWOmBpCFsENOtcUAMzzU4oo2kEqek1Am GzZeqmm+9JKuPE7FQyfbfw7DSUNIyX+FHVd4ITRWeTyifWQCQ3DI17vAwEbb9GZ1sboc23 1g5wQkSy+vd3U4ZxR2evdsyUnSZkI2I= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-575--lts_nf-OlqaLFw5pKVUAg-1; Wed, 29 Oct 2025 17:56:28 -0400 X-MC-Unique: -lts_nf-OlqaLFw5pKVUAg-1 X-Mimecast-MFC-AGG-ID: -lts_nf-OlqaLFw5pKVUAg_1761774986 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 801881800D8F; Wed, 29 Oct 2025 21:56:25 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.64.105]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E22BB19560AD; Wed, 29 Oct 2025 21:56:21 +0000 (UTC) From: Waiman Long To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Jonathan Corbet Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Andrew Morton , David Hildenbrand , Catalin Marinas , Nico Pache , Phil Auld , John Coleman , Waiman Long Subject: [PATCH v2 2/2] fs/proc: Show the content of task->user_cpus_ptr in /proc//status Date: Wed, 29 Oct 2025 17:55:55 -0400 Message-ID: <20251029215555.1006595-3-longman@redhat.com> In-Reply-To: <20251029215555.1006595-1-longman@redhat.com> References: <20251029215555.1006595-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 The task->user_cpus_ptr was introduced by commit b90ca8badbd1 ("sched: Introduce task_struct::user_cpus_ptr to track requested affinity") to keep track of user-requested CPU affinity. With commit da019032819a ("sched: Enforce user requested affinity"), user_cpus_ptr will persistently affect how cpus_allowed will be set. As child processes inherit the user_cpus_ptr setting from its parent, they may not know that their user_cpus_ptr may be set changing their CPU affinity in an unexpected way. Currently there is not an easy way to figure out if their user_cpus_ptr is set even if they have never called sched_setaffinity(2) themselves. So it makes sense to enable users to see the presence of a previously set user_cpus_ptr so they can do something about it without getting a surprise. Add new "Cpus_user" and "Cpus_user_list" fields to /proc//status output via task_cpus_allowed() as the presence of user_cpus_ptr will affect their cpus_allowed cpumask. The new fields will be empty if user_cpus_ptr isn't set. Signed-off-by: Waiman Long --- Documentation/filesystems/proc.rst | 3 +++ fs/proc/array.c | 9 +++++++++ 2 files changed, 12 insertions(+) diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 0b86a8022fa1..4317c79a530f 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -291,6 +291,9 @@ It's slow but very precise. SpeculationIndirectBranch indirect branch speculation mode Cpus_allowed mask of CPUs on which this process may run Cpus_allowed_list Same as previous, but in "list format" + Cpus_user mask of user requested CPUs from + sched_setaffinity(2), empty if not defined + Cpus_user_list Same as previous, but in "list format" Mems_allowed mask of memory nodes allowed to this process Mems_allowed_list Same as previous, but in "list format" voluntary_ctxt_switches number of voluntary context switches diff --git a/fs/proc/array.c b/fs/proc/array.c index 2ae63189091e..17e700556daa 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -403,10 +403,19 @@ static inline void task_context_switch_counts(struct seq_file *m, static void task_cpus_allowed(struct seq_file *m, struct task_struct *task) { + cpumask_t *user_cpus = task->user_cpus_ptr; + seq_printf(m, "Cpus_allowed:\t%*pb\n", cpumask_pr_args(&task->cpus_mask)); seq_printf(m, "Cpus_allowed_list:\t%*pbl\n", cpumask_pr_args(&task->cpus_mask)); + + if (user_cpus) { + seq_printf(m, "Cpus_user:\t%*pb\n", cpumask_pr_args(user_cpus)); + seq_printf(m, "Cpus_user_list:\t%*pbl\n", cpumask_pr_args(user_cpus)); + } else { + seq_puts(m, "Cpus_user:\nCpus_user_list:\n"); + } } static inline void task_core_dumping(struct seq_file *m, struct task_struct *task) -- 2.51.0