From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92F2AFA372A for ; Wed, 16 Oct 2019 15:54:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A84720650 for ; Wed, 16 Oct 2019 15:54:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571241253; bh=VanuJ71RvvI5sjdozyr9x7rrGpfPj3c8ybI0pGjZh9g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Bn2EbKqXH7JlEqPnprY/8hET/Rbpeg+o3zDs8y/EIQSw6ReFtLKxaMcL1cWbCyuix +g7zG43x3OI0sY0RVAEHE5fBIkzvJxNXnnzgR8sV4hX7HOLHT5NDCFmW89EfzeIhcO RjjhFhot8uKR9DYstyYPh1FIxTfLltoS5UdzmodI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405916AbfJPPyM (ORCPT ); Wed, 16 Oct 2019 11:54:12 -0400 Received: from mail-qk1-f193.google.com ([209.85.222.193]:43565 "EHLO mail-qk1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405903AbfJPPyL (ORCPT ); Wed, 16 Oct 2019 11:54:11 -0400 Received: by mail-qk1-f193.google.com with SMTP id h126so23207747qke.10; Wed, 16 Oct 2019 08:54:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=0WPO79DQDmX9K5UUvDG9NIvgYir9s6WI5TJKIJkxgcM=; b=KCKGbCnnZALErjaIOXUYlE+dIZkF5JwVP/bpZ27+TuqqGH9oF0ds351xGOTB7cX87c c4943D0f6UUJc5cY4nDXJIhYnPI8ba57pzg6LD+UtawPccJUsKjuyd0K8Y6vM2/hJm5I RflHR2EyV1blt1g8DVrTRsNn+6EwcKLXhSqsK6OznGPFaYfeKCajl+kZriwEBFPPtDIC LGwjAz89030aFNhbBaWQtFZnJTGGXoLm4aPpNSC1rj5FOBJXVMSkAZGyhvXwt8cU8Ppo 1pTL4woX4HN5aiZXh64itUXu4jap71Aba4sJGmNQlXnuRmfaDnNtUd8f4WP9tHxpEf67 KKXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=0WPO79DQDmX9K5UUvDG9NIvgYir9s6WI5TJKIJkxgcM=; b=cNAR3KtXW+5S96RcMbualKEeWbYNHyBu2nz7xJkLbxfGHCpHjYHnIfEZ0PVIjnLg60 /4OKmYU1mirnTYYwEKeuykLjM/Uu9n+S7MRadHAtJz17YQCDw8+l2XBvSwj4u7Zxi3d5 t1P9bu4OWFWaMKQB2ua00X65xN1pl7cpS0a43xxtNBfaxhIKUUGyFNCsJ+Vs/yZWdm2A HdURnkMokfyVwkkFQLskztrY0KKNOO21C7ZwpN3Ew9+brbcfBgrcgTyOwIGwyIc/L4mo vbLg5/hnWo1QWhu2kopSAu1FzKJIqEbeYCOLnhWx1cbXXIsM/TN6Gp5zPyMLY54LctJR eTig== X-Gm-Message-State: APjAAAXlS4AuDcpmmM6CzWWcBtoKrYvU/nGS7/paNQkj26aNM9V2aXpO jXvgCxs0lOWVfZFwnoNP284= X-Google-Smtp-Source: APXvYqwBOCFb3TTsHBTEWw1SzJD1ztkfhHtDDk3aI2+Pj7u5QuOWjlAz0L3mRgFVS7r/KKRiaPiqBw== X-Received: by 2002:a37:db0a:: with SMTP id e10mr4290823qki.3.1571241250379; Wed, 16 Oct 2019 08:54:10 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::1:2d57]) by smtp.gmail.com with ESMTPSA id b4sm11832566qkd.121.2019.10.16.08.54.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 16 Oct 2019 08:54:09 -0700 (PDT) Date: Wed, 16 Oct 2019 08:54:07 -0700 From: Tejun Heo To: Aleksa Sarai Cc: Li Zefan , Johannes Weiner , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] cgroup: pids: use {READ,WRITE}_ONCE for pids->limit operations Message-ID: <20191016155407.GP18794@devbig004.ftw2.facebook.com> References: <20191012010539.6131-1-cyphar@cyphar.com> <20191014154136.GF18794@devbig004.ftw2.facebook.com> <20191014155931.jl7idjebhqxb3ck3@yavin.dot.cyphar.com> <20191014163307.GG18794@devbig004.ftw2.facebook.com> <20191016083218.ttsaqnxpjh5i5bgv@yavin.dot.cyphar.com> <20191016142756.GN18794@devbig004.ftw2.facebook.com> <20191016152946.34j5x45ko5auhv3g@yavin.dot.cyphar.com> <20191016153520.zet5mn5xsygig4xc@yavin.dot.cyphar.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191016153520.zet5mn5xsygig4xc@yavin.dot.cyphar.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 17, 2019 at 02:35:20AM +1100, Aleksa Sarai wrote: > > Sure, I will switch it to use atomic64_read() and atomic64_set() instead > > if that's what you'd prefer. Though I will mention that on quite a few > > architectures atomic64_read() is defined as: > > > > #define atomic64_read(v) READ_ONCE((v)->counter) > > Though I guess that's because on those architectures it turns out that > READ_ONCE is properly atomic? Oh yeah, on archs where 64bit accesses are atomic, READ_ONCE() / WRITE_ONCE() would work here. If the limit variable were ulong instead of an explicit 64bit variable, RW ONCE would work too as ulong accesses are atomic on all archs IIRC. Thanks. -- tejun