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=-9.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 BB4ACC76186 for ; Wed, 24 Jul 2019 16:48:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9223921926 for ; Wed, 24 Jul 2019 16:48:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="uaGBcyfD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387725AbfGXQsY (ORCPT ); Wed, 24 Jul 2019 12:48:24 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:40445 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387551AbfGXQsY (ORCPT ); Wed, 24 Jul 2019 12:48:24 -0400 Received: by mail-pl1-f194.google.com with SMTP id a93so22183729pla.7 for ; Wed, 24 Jul 2019 09:48:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=gRKAY+MZWKaqd0CuoSyZlDBPmUfGcGm8988bda4hVss=; b=uaGBcyfDCm3TTg2hgJyfh2501WHhM6A8JDweTlaQFVUGuJ6Ekd9vkgtWwjLp2xuYbs w31WEox/uK++rZpnzcVXYQC3Z58XUOEv1IySt81cZPSUZMQcF3MXA+8A4fs7oub651dj FplFBDvJ3JJ/RWNd/FCP9VaI9K9cAUJFyXu/w= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=gRKAY+MZWKaqd0CuoSyZlDBPmUfGcGm8988bda4hVss=; b=YUi4DX7mY0R4vcAnFUJ6t6GstQ0pvmYlY/4nfVnFRBk3F5Z6hRh1/OcbViQdzycGtP 5RMbhMzdUVnFAZA4U7ZIHCreB19XWhLUKneM0zaXGkRraIyNpc7fAAKULLOvPKIf2QaL FiWS86cRt5L5tIA6afQWopEIr0IALtKcN2k6NHLzWjOuLP6Z8SpRKfLWkFFmp1KJfme/ y8PGHvUm/lzAyq2N0DrxfEBOx4mdsIK50oHQH9eQ1K5UkUy2UYSafT5z6w5yIZE6RcwF HJN2Th+96h2ajg1G7r+QO2JgpYKsDlLorJ5+n1Bl1AJFYbROaiN18rn6E1r8nNemxTDO HqmA== X-Gm-Message-State: APjAAAXhozIipbbYsAuIKv2w8669B7sldkRqob8uv8bBqqXQOgb2xsq7 s/9xMSW25lnQWHGxv4FvcnL+ZjsQ X-Google-Smtp-Source: APXvYqxmKuaKat7f823FoVvgzFEjTDwsr672WnIYsS6sAhsU7sn7o+WU6yHFNUJVOZCVzd6xfNA0mA== X-Received: by 2002:a17:902:9689:: with SMTP id n9mr87959674plp.241.1563986902928; Wed, 24 Jul 2019 09:48:22 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id v7sm4148876pff.87.2019.07.24.09.48.21 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 24 Jul 2019 09:48:22 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Andrew Morton , Arnd Bergmann , Christian Brauner , "Eric W. Biederman" , Oleg Nesterov Subject: [PATCH] pidfd: Add warning if exit_state is 0 during notification Date: Wed, 24 Jul 2019 12:48:16 -0400 Message-Id: <20190724164816.201099-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.657.g960e92d24f-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Previously a condition got missed where the pidfd waiters are awakened before the exit_state gets set. This can result in a missed notification [1] and the polling thread waiting forever. It is fixed now, however it would be nice to avoid this kind of issue going unnoticed in the future. So just add a warning to catch it in the future. [1] https://lore.kernel.org/lkml/20190717172100.261204-1-joel@joelfernandes.org/ Signed-off-by: Joel Fernandes (Google) --- kernel/signal.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/signal.c b/kernel/signal.c index 91b789dd6e72..349f5a67f100 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1885,6 +1885,7 @@ static void do_notify_pidfd(struct task_struct *task) { struct pid *pid; + WARN_ON(task->exit_state == 0); pid = task_pid(task); wake_up_all(&pid->wait_pidfd); } -- 2.22.0.657.g960e92d24f-goog