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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 592BDC43219 for ; Mon, 29 Apr 2019 14:07:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1DB0A2063F for ; Mon, 29 Apr 2019 14:07:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="U8Ck1Tbj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728307AbfD2OHq (ORCPT ); Mon, 29 Apr 2019 10:07:46 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:37811 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728180AbfD2OHq (ORCPT ); Mon, 29 Apr 2019 10:07:46 -0400 Received: by mail-pf1-f194.google.com with SMTP id g3so5376438pfi.4 for ; Mon, 29 Apr 2019 07:07:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=rVfhfQiy4k/gTXiRLKY8pcxpzGE19WyRfB5vYwX1+8s=; b=U8Ck1TbjUSL7T33txtHKdEx40f64DhMg0b6UfCIYbhcaob+mwl64qmmKmtIR1GMjcm 7H+dUkOmjfr02GvlY8b2e206hBGgohLlXfx//2BNG/ZQ96Ie6DGt1oiwutrJHEib2TqM TM5CMLULo1jBRYcURqfR7zbPDLtSuLhGqtdUs= 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=rVfhfQiy4k/gTXiRLKY8pcxpzGE19WyRfB5vYwX1+8s=; b=ZcTST8OXTWTAbAqLHWvVMJLG5jHmLRrLNqwX4yMZGv/QvLSLd3RrqRqwwnFiyRlE4j MNDXL9+dSyiAVXQZ+goo5aZGevP97r7gQ/lBOXktwc4PKrz25So+lk8GeTBxZx5Ts2b2 O5VYwoBS+T1lrRSCglxBH1Fhy0F+aeGD7Y4jU1BBtD3CY//M5CPuPEjcQzM2J0+sgsEB LYkVspEXwu2k6WnYPNmzLjUI5+idzkeE0tZiKLyLzhtLdNiSGU3I7lXxrPeJ+INWiQrf uG6rvCzbvlHcgc+230VjAe8hVjfu9aJ6t3tf8cFQTVzoyy2lXyJyvok3ppfCF4R4ANFS mckA== X-Gm-Message-State: APjAAAXIH6zArmFqf3puuI4IFCOGbFlVOWRKSqv0pnkdkowwmGhg4DIB 814fZ9nAcYPmQJ/HDN2nZkGCQA== X-Google-Smtp-Source: APXvYqzx1BE0CcVj4OJwmwL/GX1uNg3HWoq8XL9akQxqUrC4o0fWEAE4fgtWIdkNuX9GU1q+NUN06w== X-Received: by 2002:aa7:92c4:: with SMTP id k4mr32352058pfa.183.1556546865597; Mon, 29 Apr 2019 07:07:45 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id 128sm39979866pgb.47.2019.04.29.07.07.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 29 Apr 2019 07:07:44 -0700 (PDT) Date: Mon, 29 Apr 2019 10:07:43 -0400 From: Joel Fernandes To: Oleg Nesterov Cc: Christian Brauner , linux-kernel@vger.kernel.org, luto@amacapital.net, rostedt@goodmis.org, dancol@google.com, sspatil@google.com, jannh@google.com, surenb@google.com, timmurray@google.com, Jonathan Kowalski , torvalds@linux-foundation.org, kernel-team@android.com, Andrew Morton , Arnd Bergmann , "Eric W. Biederman" , Greg Kroah-Hartman , Ingo Molnar , Jann Horn , linux-kselftest@vger.kernel.org, Michal Hocko , "Peter Zijlstra (Intel)" , Serge Hallyn , Shuah Khan , Stephen Rothwell , Thomas Gleixner , Tycho Andersen , viro@zeniv.linux.org.uk, linux-api@vger.kernel.org Subject: Re: [PATCH v1 1/2] Add polling support to pidfd Message-ID: <20190429140743.GB173743@google.com> References: <20190425190010.46489-1-joel@joelfernandes.org> <20190425222359.sqhboc4x4daznr6r@brauner.io> <20190428162405.GA6757@redhat.com> <20190429140245.GB233442@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190429140245.GB233442@google.com> 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 Mon, Apr 29, 2019 at 10:02:45AM -0400, Joel Fernandes wrote: > On Sun, Apr 28, 2019 at 06:24:06PM +0200, Oleg Nesterov wrote: [snip] > > > > +{ > > > > + struct pid *pid; > > > > + > > > > + lockdep_assert_held(&tasklist_lock); > > > > + > > > > + pid = get_task_pid(task, PIDTYPE_PID); > > > > + wake_up_all(&pid->wait_pidfd); > > > > + put_pid(pid); > > > > Why get/put? > > Yes, pid_task() should do it. Will update it. Thanks! I spoke too soon. We need the task's pid of type PIDTYPE_PID. How else can we get it? This does an atomic_inc on the pid->count, so we need to put_pid() after we are done with it. Did I miss something? thanks, - Joel