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=-6.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 1D1C6C76186 for ; Wed, 24 Jul 2019 16:53:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1AA722ADA for ; Wed, 24 Jul 2019 16:53:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=brauner.io header.i=@brauner.io header.b="c5R5bL+9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727737AbfGXQxt (ORCPT ); Wed, 24 Jul 2019 12:53:49 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:43168 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726031AbfGXQxs (ORCPT ); Wed, 24 Jul 2019 12:53:48 -0400 Received: by mail-pg1-f196.google.com with SMTP id f25so21506495pgv.10 for ; Wed, 24 Jul 2019 09:53:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brauner.io; s=google; h=date:user-agent:in-reply-to:references:mime-version :content-transfer-encoding:subject:to:cc:from:message-id; bh=/6dHe5N7XGzJMTeT13e63PRDUIMz76zdv5Ig0oiXBDs=; b=c5R5bL+94MO/tiZpYHceuOOJ4pDqDaAqKI79pGgbQ3hRWblNVPM1wEBpOWShzp4JrW a1eYIt77Xz50jOpTia5iZdau+ynVq7ii3VjX6iGG2J+8izcDXKyGety2ifhyTDjh6jCj Hm5b3zwI2uAYG4yuCpIJxtyQ0g7xlgk4V30vYYhgKBqJl7rZrulpnyUuVd72VokBy4qL HUFBWNShWnvsOXyuCjTdEq3XDeG9lDCKA6thApkomT751L/hvSe7PmkqAq45wV+JE7IU QtuQQw2oTKqIKbMXJ0vPipk/UXD/aCitGR55+kQcwRWmS61BLPcNgL8Rsj1kAi0/j9tJ Wfng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:user-agent:in-reply-to:references :mime-version:content-transfer-encoding:subject:to:cc:from :message-id; bh=/6dHe5N7XGzJMTeT13e63PRDUIMz76zdv5Ig0oiXBDs=; b=slPpDSOrTCtEhGOZkPBWYQC5Q2O1Bpjm5+3DevXswmInw26K0UWNakCmn3Kh1Ir5Mw aI2t8yK9C6vFcVFrY9gEVsSkCQveK5243q4RsLKAefU2cHxRTsSrJQn3Z/VPUmDhLFE2 QQxJ0H+hXektuZa+Gnwr7mpXKLuy664KdG8nyDoYjiodTZ1LmHI/nCzmJT4B3Pe1BYV6 sTigetkdMowHnxqrMOGHY7/tnrtCGerFJEjwiWlLS2XEMYO882/5U0S6UrmvXjcOPCHh Gx7U6d9Vtl5/KlAnAVPpwzDKHeqNHUmK9CyDZgn4HmcTxnHih2AKmL4JGsNeUXikD/2a R77Q== X-Gm-Message-State: APjAAAXOp9LpLAsGSXIZ+CukSiBDrReyqe3pkNxlDr4kK/nkpszkdBSD WJLNot68l281PaTn61oXZuU= X-Google-Smtp-Source: APXvYqysLzlNEq51DdxReWz4dfSxNanv1GpI4EeAG7Zf+3MfJV32v94v1OwKZyF1793+7wCG+KmLZQ== X-Received: by 2002:aa7:8502:: with SMTP id v2mr11966032pfn.98.1563987227909; Wed, 24 Jul 2019 09:53:47 -0700 (PDT) Received: from [25.171.251.59] ([172.58.27.54]) by smtp.gmail.com with ESMTPSA id q126sm2974497pfb.56.2019.07.24.09.53.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jul 2019 09:53:47 -0700 (PDT) Date: Wed, 24 Jul 2019 18:53:39 +0200 User-Agent: K-9 Mail for Android In-Reply-To: <20190724164816.201099-1-joel@joelfernandes.org> References: <20190724164816.201099-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH] pidfd: Add warning if exit_state is 0 during notification To: "Joel Fernandes (Google)" , linux-kernel@vger.kernel.org CC: Andrew Morton , Arnd Bergmann , "Eric W. Biederman" , Oleg Nesterov From: Christian Brauner Message-ID: <3724AB8D-81A8-40B7-A025-95CD6BAAA6D8@brauner.io> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On July 24, 2019 6:48:16 PM GMT+02:00, "Joel Fernandes (Google)" wrote: >Previously a condition got missed where the pidfd waiters are awakened >before the exit_state gets set=2E This can result in a missed >notification >[1] and the polling thread waiting forever=2E > >It is fixed now, however it would be nice to avoid this kind of issue >going unnoticed in the future=2E So just add a warning to catch it in the >future=2E > >[1] >https://lore=2Ekernel=2Eorg/lkml/20190717172100=2E261204-1-joel@joelferna= ndes=2Eorg/ > >Signed-off-by: Joel Fernandes (Google) >--- > kernel/signal=2Ec | 1 + > 1 file changed, 1 insertion(+) > >diff --git a/kernel/signal=2Ec b/kernel/signal=2Ec >index 91b789dd6e72=2E=2E349f5a67f100 100644 >--- a/kernel/signal=2Ec >+++ b/kernel/signal=2Ec >@@ -1885,6 +1885,7 @@ static void do_notify_pidfd(struct task_struct >*task) > { > struct pid *pid; >=20 >+ WARN_ON(task->exit_state =3D=3D 0); > pid =3D task_pid(task); > wake_up_all(&pid->wait_pidfd); > } Makes sense to me=2E I'm picking this up unless someone sees a problem with this patch=2E Reviewed-by: Christian Brauner