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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 9E471C43441 for ; Tue, 13 Nov 2018 20:58:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F5F9223AE for ; Tue, 13 Nov 2018 20:58:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="FLZWfjcs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F5F9223AE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728718AbeKNG6a (ORCPT ); Wed, 14 Nov 2018 01:58:30 -0500 Received: from mail-yb1-f193.google.com ([209.85.219.193]:37866 "EHLO mail-yb1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725892AbeKNG63 (ORCPT ); Wed, 14 Nov 2018 01:58:29 -0500 Received: by mail-yb1-f193.google.com with SMTP id d18-v6so6003199yba.4; Tue, 13 Nov 2018 12:58:35 -0800 (PST) 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=S60uROdWn0WL7K7ecFcE3+FHfbw6BesWS23KZQCAEPE=; b=FLZWfjcsr1Gt3kuyzezxsRzj3iWOkeZzbXJIqDPo/+0ZtHx68ZPEyW0xbRT5/qIRI6 TiuMMbEGmcrxOx3P7/z6n6jYNgBfk/jCV6XSMl6Pgg/ZLQYQgBWZlk4wJAlQCLZzramo eNT0CrG3P1/3nL6/EYg0EvvdD8GtNAL8P1pme8+9hFvGXzLyd83GJgJQv9lbXhPEod4E 2WGgRw7RIaTw8S45D1FUr5KC9B7qmElhvXPIZh+R3rCfWAx1pb3ILp9/fQFhUSiuMB9R ed6qNoRHYCw8v/r9JcnIMjgDDk8CghN/k8nnWEwNnZxpqUJv118YUf8nrnomhAbPWh0R P6vg== 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=S60uROdWn0WL7K7ecFcE3+FHfbw6BesWS23KZQCAEPE=; b=TaLJ8MJzOOArETKB8pQSk/6zAvCQrcAiGkFW+AZvUXUTsZjjZzJqgzmQGGtDEu8XWO pt6WAtX6xuef/Vpn/6sZJR5i+LcZ2FvfphfSrafSVyVujgedh8qIfCCJ2FhLVn59orO+ wk2cDiFEW8B9Gq7Q6O/R5h5GzWiK3o78vt0ZapnV73Luz/YOgb7TKz3rMLvMYLpoVjRJ 1kMFaNVDDduUdyEwBJoDUqhwVVTRWmD5NEY80w7CLQm/3KWQYvx17J3pXIS+yH+OEK6i 2KJ36V6xtwZdEkppRViwwAnV/HEUcd6soIeJ1ojjGbnLiHNmehkPXYh2uySFR0FU/ygF Ddqg== X-Gm-Message-State: AGRZ1gLG3clTSIOQeGTBKDJY6aHsfYDz7F9i4beEbQjIKI+ZVnGtE9RX OBflUzMx3uV9HDXfIHmL0qA= X-Google-Smtp-Source: AJdET5feeNzahH4L8A+jwhba+JdaniS1Uagf2yOhTCwKhBsb3ft64WM5dSOXWPS/3uXhva9mKWasww== X-Received: by 2002:a25:8311:: with SMTP id s17-v6mr6807075ybk.142.1542142714568; Tue, 13 Nov 2018 12:58:34 -0800 (PST) Received: from localhost ([2620:10d:c091:200::6:e2a7]) by smtp.gmail.com with ESMTPSA id c6-v6sm15635059ywh.34.2018.11.13.12.58.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Nov 2018 12:58:33 -0800 (PST) Date: Tue, 13 Nov 2018 12:58:31 -0800 From: Tejun Heo To: Roman Gushchin Cc: Roman Gushchin , Oleg Nesterov , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Kernel Team , Linus Torvalds , Andrew Morton , Ingo Molnar Subject: Re: [PATCH v2 3/6] cgroup: cgroup v2 freezer Message-ID: <20181113205831.GP2509588@devbig004.ftw2.facebook.com> References: <20181112230422.5911-1-guro@fb.com> <20181112230422.5911-5-guro@fb.com> <20181113020817.GE2509588@devbig004.ftw2.facebook.com> <20181113184751.GB21629@tower.DHCP.thefacebook.com> <20181113191541.GM2509588@devbig004.ftw2.facebook.com> <20181113205507.GB15590@tower.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181113205507.GB15590@tower.DHCP.thefacebook.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 Tue, Nov 13, 2018 at 08:55:11PM +0000, Roman Gushchin wrote: > > > > > + if (lock_task_sighand(task, &flags)) { > > > > > + if (test_bit(CGRP_FREEZE, &dst->flags)) > > > > > + task->jobctl |= JOBCTL_TRAP_FREEZE; > > > > > + else > > > > > + task->jobctl &= ~JOBCTL_TRAP_FREEZE; > > > > > > > > How are these flags synchronized? > > > > > > Using the css_set_lock. > > > > But other JOBCTL_TRAP bits aren't synchronized by css_set_lock, right? > > But if we don't touch this bit anywhere else, should be fine, right? But other JOBCTL_TRAP_ bits aren't synchronized with css_set_lock, so they can be updated (read-modify-write) concurrently and clobber each other, no? Thanks. -- tejun