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=-11.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 BC82BC47420 for ; Fri, 25 Sep 2020 06:09:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D06021775 for ; Fri, 25 Sep 2020 06:09:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="dD5keCca" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727290AbgIYGJs (ORCPT ); Fri, 25 Sep 2020 02:09:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727135AbgIYGJs (ORCPT ); Fri, 25 Sep 2020 02:09:48 -0400 Received: from mail-ua1-x944.google.com (mail-ua1-x944.google.com [IPv6:2607:f8b0:4864:20::944]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E347C0613D4 for ; Thu, 24 Sep 2020 23:09:48 -0700 (PDT) Received: by mail-ua1-x944.google.com with SMTP id u48so569826uau.0 for ; Thu, 24 Sep 2020 23:09:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+Gekh1/5HoSJgzGHBdPAl6wdzLsESdx094pfUMDJNyY=; b=dD5keCca5UgZ+EkGaoslYMH6ugraBNwjEpWR+NeC67ssf+Snq7vYe3XpYQ7kzkqMKz Sm19c1aeIJMEIuC7O+mIAJDQ4GaduImiLb8BwTm/ijJo/9/RLR6zG9UFvkrMiIl/LfGV a8iQ4bTXB38uRWc2wFr/Tg+pgiR4/WnsCAUXlAz4D2AzOHt372+ILQ3QpEr85DCqDmoI 0qrscfR//nr/b1WyvAfUKdycS2Gqnk/zzMU5nxViEninjYR2SqXS5Vwc0k0zj5pbO/WJ jxHVuJs1GCPTxtgHn5l9JxRSNMQbaMoBlUmELwE8Jd2o2T8e4Jv5Oac3vVxusY3hsN3z R95Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+Gekh1/5HoSJgzGHBdPAl6wdzLsESdx094pfUMDJNyY=; b=jkRmuiUcYPo2vf11c4Ibkt2hlcgwubvBy7keNZYgdbhVQwwKFGsdN9ylwm40mbszNq 18VNjT9zXK8eB+0HF4XyJCW4ZxnJE/BGBlGSTQsND+v7ASm0B8DFBAwIvJ5LhTzxLz50 KXpzx5PE41Z6I5WxMoVwUhBDjAktfi3IiS6N8HlP2KOwA8Y5L1YDx3/GgtbIPYZmgwhU lrd/B1jpUiDhjTW5Mo9kkGJWp9HmmyqzcDS7XkslsS5pgWF4y9CHJchD70xBHYozdstJ WP+iTHfGJHtEEpuf3MENLX1nJjBqRTxPGRGbu4ksd9Z2DhzcdRY6XZR9mx1HjtlzIF38 O7fg== X-Gm-Message-State: AOAM53086Vm1qhcEcZx4DnifHZAwI4jCnwZmJJDSxqp7JYOvofoB4UpZ QCzghqG7k9KAozF8oi0SP3r4eao5xLKxUlPffttJGw== X-Google-Smtp-Source: ABdhPJws0yBakJxLSgvK/0x/1OQPz7YxRxkZQcqwZiHxwegfJTqjSbUaJljKms2pqCM5u1+NBYuCQeQxme7+GWDW+OM= X-Received: by 2002:a9f:29c5:: with SMTP id s63mr1581180uas.34.1601014186979; Thu, 24 Sep 2020 23:09:46 -0700 (PDT) MIME-Version: 1.0 References: <20200924143317.getruzwu423g3o3e@wittgenstein> <20200924162126.mbthwz32w7rba7oe@wittgenstein> In-Reply-To: <20200924162126.mbthwz32w7rba7oe@wittgenstein> From: Naresh Kamboju Date: Fri, 25 Sep 2020 11:39:35 +0530 Message-ID: Subject: Re: selftests: pidfd: pidfd_wait hangs on linux next kernel on all devices To: Christian Brauner Cc: "open list:KERNEL SELFTEST FRAMEWORK" , linux-api@vger.kernel.org, open list , Christian Brauner , Kees Cook , "Peter Zijlstra (Intel)" , Ingo Molnar , Thomas Gleixner , Oleg Nesterov , "Eric W. Biederman" , Sargun Dhillon , Aleksa Sarai , Josh Triplett , Jens Axboe , Shuah Khan , lkft-triage@lists.linaro.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Sep 2020 at 21:51, Christian Brauner wrote: > > On Thu, Sep 24, 2020 at 04:33:17PM +0200, Christian Brauner wrote: > > On Wed, Sep 23, 2020 at 07:52:05PM +0530, Naresh Kamboju wrote: > > > selftests: pidfd: pidfd_wait hangs on linux next kernel on x86_64, > > > i386 and arm64 Juno-r2 > > > These devices are using NFS mounted rootfs. > > > I have tested pidfd testcases independently and all test PASS. > > > > > > The Hang or exit from test run noticed when run by run_kselftest.sh > > > > > > pidfd_wait.c:208:wait_nonblock:Expected sys_waitid(P_PIDFD, pidfd, > > > &info, WSTOPPED, NULL) (-1) == 0 (0) > > > wait_nonblock: Test terminated by assertion > > > > > > metadata: > > > git branch: master > > > git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > > git commit: e64997027d5f171148687e58b78c8b3c869a6158 > > > git describe: next-20200922 > > > make_kernelversion: 5.9.0-rc6 > > > kernel-config: > > > http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/intel-core2-32/lkft/linux-next/865/config > > > > > > Reported-by: Naresh Kamboju > > > > Thanks for reproting this. I'm taking a look now! > > Ok, this is a simple race in the selftests, that I overlooked and which > is more likely to hit when there's a lot of processes running on the > system. Basically the child process hasn't SIGSTOPed itself yet but the > parent is already calling waitid() on a O_NONBLOCK pidfd. Since it > doesn't find a WSTOPPED process it returns -EAGAIN correctly. > > The fix for this is to move the line where we're removing the O_NONBLOCK > property from the fd before the waitid() WSTOPPED call so we hang until > the child becomes stopped. > > So I believe the fix is: This patch applied and scheduled for kselftest full test run. > > diff --git a/tools/testing/selftests/pidfd/pidfd_wait.c b/tools/testing/selftests/pidfd/pidfd_wait.c > index 4063d6f31fa4..be2943f072f6 100644 > --- a/tools/testing/selftests/pidfd/pidfd_wait.c > +++ b/tools/testing/selftests/pidfd/pidfd_wait.c > @@ -205,6 +205,8 @@ TEST(wait_nonblock) > ret = sys_waitid(P_PIDFD, pidfd, &info, WEXITED | WNOHANG, NULL); > ASSERT_EQ(ret, 0); > > + ASSERT_EQ(fcntl(pidfd, F_SETFL, (flags & ~O_NONBLOCK)), 0); > + > ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WSTOPPED, NULL), 0); > ASSERT_EQ(info.si_signo, SIGCHLD); > ASSERT_EQ(info.si_code, CLD_STOPPED); > @@ -212,8 +214,6 @@ TEST(wait_nonblock) > > ASSERT_EQ(sys_pidfd_send_signal(pidfd, SIGCONT, NULL, 0), 0); > > - ASSERT_EQ(fcntl(pidfd, F_SETFL, (flags & ~O_NONBLOCK)), 0); > - > ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WEXITED, NULL), 0); > ASSERT_EQ(info.si_signo, SIGCHLD); > ASSERT_EQ(info.si_code, CLD_EXITED); > > Christian - Naresh