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_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 D129FC6778D for ; Tue, 11 Sep 2018 05:41:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 234B520854 for ; Tue, 11 Sep 2018 05:41:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="nLWej1bg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 234B520854 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com 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 S1726840AbeIKKjK (ORCPT ); Tue, 11 Sep 2018 06:39:10 -0400 Received: from mail-pg1-f173.google.com ([209.85.215.173]:41358 "EHLO mail-pg1-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726274AbeIKKjK (ORCPT ); Tue, 11 Sep 2018 06:39:10 -0400 Received: by mail-pg1-f173.google.com with SMTP id s15-v6so11651242pgv.8; Mon, 10 Sep 2018 22:41:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=lWNX0+9g0p0SQsBRlm5zPRffGGsTTVk7JxlEp7OQ3JQ=; b=nLWej1bgtEVhw12Ik8cEl/ywaSJowNJG9IWI9lQvQLDRs47xLOd48fpl5t5JCZNMK1 ZPSndQQ9f5uuOXBcszh5AvHHEN6JyDu8suJCIpSF9HeYzMB5+HeJYezLLXNbp4iyZ4QX iJ59+WkyP70+AtOvbrTwDw0pqAiH7RpE61cRhYUHf1/3gg150l7hnzi83WCpQpX45DUm nYEJ4oj8T+87Ultp7hEA/po4FWnLrhIoCvrd8uwCuJr6UcNrPjxozaxGjUp1MNXWtJVd xrCJVzB/QnMkztiOrH2aSPbe+/R5bTn7HVtm4X9EHlhJe59NsRvP/3q8LXhHxBhW/Pme AJ1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=lWNX0+9g0p0SQsBRlm5zPRffGGsTTVk7JxlEp7OQ3JQ=; b=IBEZpEb7fUQYWJqmNREbZV7dKsJCCLVeAegKwgdyBkZlTU+VE7UQWK3yHose/Szg0Y M/lnlb4H7fEQtPhsYzdyPWsl5cseh1OWmwIdufo1SQUBNrFXtNJhXhKt4aH0TULqADNU m71j3TInikss8MuL6gsc+VNDEg7jUaev/78BnDUih8IieUCKfg5eU5dlGgrzW/96Czvs 5SQbXr0VRUNaZ+rZal5koVP74YybJrgf2FtBTz1F91lqGnerbDe3dRiJ6+bRT63DYeT/ za2IwvatT6p1UY3lYizwSQx80z9ltpeFBUZ3Ho5bzcbVMwblvJETXpxY9+FNOEMhLmXE zvVA== X-Gm-Message-State: APzg51DCBo/1QwdXPIke5ZSO+OXObt7DkWw+edPNO9Q5wgnz9+Lm/Lam kX2Hor8Svxm9/Cn28aeZ0Dg= X-Google-Smtp-Source: ANB0VdbxQ43h8Vii//ReyeHjYNB5mK/icBmw2JSkwyb3kJHRc6oey5PlGA5H+hXw99rbruwWLWYIyg== X-Received: by 2002:a63:e70e:: with SMTP id b14-v6mr26243956pgi.68.1536644494740; Mon, 10 Sep 2018 22:41:34 -0700 (PDT) Received: from localhost ([39.7.19.225]) by smtp.gmail.com with ESMTPSA id x2-v6sm31396515pfi.166.2018.09.10.22.41.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 10 Sep 2018 22:41:33 -0700 (PDT) Date: Tue, 11 Sep 2018 14:41:29 +0900 From: Sergey Senozhatsky To: Dmitry Safonov Cc: linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Daniel Axtens , Dmitry Vyukov , Michael Neuling , Mikulas Patocka , Nathan March , Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= , Peter Hurley , "Rong, Chen" , Tan Xiaojun , Tetsuo Handa , stable@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby , Peter Zijlstra , "Paul E. McKenney" , Sergey Senozhatsky Subject: Re: [PATCHv3 2/6] tty/ldsem: Update waiter->task before waking up reader Message-ID: <20180911054129.GC4065@jagdpanzerIV> References: <20180911014821.26286-1-dima@arista.com> <20180911014821.26286-3-dima@arista.com> <20180911050449.GB4065@jagdpanzerIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180911050449.GB4065@jagdpanzerIV> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (09/11/18 14:04), Sergey Senozhatsky wrote: > > for (;;) { > > set_current_state(TASK_UNINTERRUPTIBLE); > > I think that set_current_state() also executes memory barrier. Just > because it accesses task state. > > > - if (!waiter.task) > > + if (!READ_ONCE(waiter.task)) > > break; > > if (!timeout) > > break; This READ_ONCE(waiter.task) looks interesting. Maybe could be moved to a loop condition while (!READ_ONCE(waiter.task)) { ... } -ss