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 79F12C4CECE for ; Mon, 14 Oct 2019 15:41:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4395820873 for ; Mon, 14 Oct 2019 15:41:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571067701; bh=ymV5LEDVb8aHsr4Q8NYWv+K5Y1QpcdPwCL6+ZBDnL2M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=LQCZNylfQt24T/37F1hpWQkN/7ny6VqW9yuqerwVwCAO9f60KO8kf94k9NfeF8Uxw 6FOzoCUiqroL8ErXa9RAd1qhp9REq5gCPlp77yl7rdwizG/vs2KqYrAvsR06ETyobv Yv/ldx5ezY9XQau355jct8Ir0MDzHoPkNZ++kK5E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731008AbfJNPlk (ORCPT ); Mon, 14 Oct 2019 11:41:40 -0400 Received: from mail-qk1-f196.google.com ([209.85.222.196]:36800 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731457AbfJNPlk (ORCPT ); Mon, 14 Oct 2019 11:41:40 -0400 Received: by mail-qk1-f196.google.com with SMTP id y189so16290892qkc.3; Mon, 14 Oct 2019 08:41:39 -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=BUs6ww2wp2HkRKO5Ig1yFUSfYWRm/mJFXsejJnbtOqs=; b=oQOzhgiLemf2MFAncmQNwr1h9wmPYZjB9Mhg6CjWxiGAzLmQaUUeRd3rfj1VMVUgXB T/o3WuHsOpozELcayBmb+2CMX2fA22LFOds2rvcs7WSjLFP2WyZn5MlPTOwV0zJEUGk/ 0AH3sWGN4COj6efHDv2YZyJZGaaUl/5jK7q8NriAucA/qduGE/SI5d3R8Kq47J5m2EXo AP2tAQNe4qD4gD8HfxptPoFq51uauD9hmaTSpJmi6PdyFi/oYoXjibGgvoME/Pzo/d3Y 7pv6CwmKL8neIiyMfpoFvvqHNK7ArxkXw1SmJyNxDEi5/K0k6Cd9X3hcnMsDpkSu1bUO /G1A== 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=BUs6ww2wp2HkRKO5Ig1yFUSfYWRm/mJFXsejJnbtOqs=; b=G4AAw2jhzNI4PL0K2aVdIemeTkbuKlVHFnWUEvUcTnxF15VOcfOVu61KrSotSFV6kf p3FOrqX+uPG9a9emycij6j50iCG5q5+GpawRoSXhnos9ISzyZxnJhhNKYsSJa/2OSDPJ WKOkiKjwzhSdGqvBTkv/mxI5a1rkMS20zhoSP/DdpcIw37hEMrp6BIBbL6G0+d2MG9+w joj6B688sUo7eOd99dSii3q4u83Qiyl0M7XkFFnnNEGrcWyGjnnKjOUNj8slPWkbhWVf G7MVLeBYVJHvUhUnrb1vAbOHjjcd0orzdhKBI39khT8x1+XjIcWwwllfQwuv9yZU3ymo dFBg== X-Gm-Message-State: APjAAAWLnftbc/ZoibBYV/Xnr8m97g4EgbUEG/B+618L8bmFCUfcW+zX lw5omnY2eYAJCwhG6WSXvlQ= X-Google-Smtp-Source: APXvYqw6h4Cle6f9ZGijs+B74SXDMAHKmu3JulWpk9p6jKiLNU22tm/HqcYx2y0bbEjKhUbAETn66g== X-Received: by 2002:a05:620a:887:: with SMTP id b7mr27937691qka.186.1571067698911; Mon, 14 Oct 2019 08:41:38 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::1:50c5]) by smtp.gmail.com with ESMTPSA id c20sm7453462qkm.11.2019.10.14.08.41.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Oct 2019 08:41:38 -0700 (PDT) Date: Mon, 14 Oct 2019 08:41:36 -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: <20191014154136.GF18794@devbig004.ftw2.facebook.com> References: <20191012010539.6131-1-cyphar@cyphar.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191012010539.6131-1-cyphar@cyphar.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sat, Oct 12, 2019 at 12:05:39PM +1100, Aleksa Sarai wrote: > Because pids->limit can be changed concurrently (but we don't want to > take a lock because it would be needlessly expensive), use the > appropriate memory barriers. I can't quite tell what problem it's fixing. Can you elaborate a scenario where the current code would break that your patch fixes? Thanks. -- tejun