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=-0.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 3F4DCC4320A for ; Mon, 2 Aug 2021 07:19:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2342460F11 for ; Mon, 2 Aug 2021 07:19:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232443AbhHBHTg (ORCPT ); Mon, 2 Aug 2021 03:19:36 -0400 Received: from mout.gmx.net ([212.227.17.22]:35675 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231649AbhHBHTc (ORCPT ); Mon, 2 Aug 2021 03:19:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1627888716; bh=ChXftOXR8yVdG8QFcMQASenelvUXOPCJeJpZQsMwvlE=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=SmYy47/NlEiRWSDLAnRcwHnFt8iTbyLVWrc673/b1voLPOKUGd+ks+3rAzvCNmwk7 05WJHYNhgck4qOVgPR9WowK5ykGwvQ+iJTTHMFuLsbPCCuCfQTl7PfhyYwg4YWx33p Tus2fswo5drk2lZrOnBPXw1LGu3z8fwG6MbyCy7g= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from homer.fritz.box ([185.221.151.211]) by mail.gmx.net (mrgmx104 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MmlTC-1mqhGU0fvq-00jrhr; Mon, 02 Aug 2021 09:18:36 +0200 Message-ID: Subject: Re: v5.14-rc3-rt1 losing wakeups? From: Mike Galbraith To: Sebastian Andrzej Siewior Cc: Thomas Gleixner , LKML , linux-rt-users@vger.kernel.org, Steven Rostedt , Peter Zijlstra Date: Mon, 02 Aug 2021 09:18:34 +0200 In-Reply-To: <20210802070218.5js3exubjxvsicx6@linutronix.de> References: <20210730110753.jvli6alm63h5lefy@linutronix.de> <2ae27233ab091d09a7d1e971a47144b40dd51fa0.camel@gmx.de> <87pmuzsf1p.ffs@tglx> <6fce881efc3d8c24a5172528fe1f46ec2ddc0607.camel@gmx.de> <20210802070218.5js3exubjxvsicx6@linutronix.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:OrmG8K3WPQzzonRq7UWFT87Uq2HB4IWHezwt+GbZX9tGA294hhs XD8g1aR2yNbXbtoodtufOfmdEuUH4tZIMrwdtLU69dpeAz8+ZIuzQGEfg+5Ssmpkb4L71wL v6BdvznPwocY5ejD/DiCzC9odwIO7zpPL7Ke6Y/7Ncy9lmZeCzb8L6XVXG69DZXZ/K9joZz 3ZdeWFrHZMM/g7Vg6e1KA== X-UI-Out-Filterresults: notjunk:1;V03:K0:4Kt1Hr6+MTs=:fEN+JqB6ucweQH6gafMznS 4GJE9CtG1mkLkf4dDwovE0SnmDjo6CqXeS7+cNaP/kw14Vmx2BkxO3GjuyIKZZRxuDABaTkxH 0K581b0T7YC/j4GwuwALa9/d4PEUPU8pziP3y0LxYzjua8Gk0LEzixcB4qvyZDCOGfQdZQNJP 8mOueg2XqUpvoc3Ryzw4hmQleM8ALKUUSjZChaBdWXY3qWNjAKHbBgBDAVZQLPqicYatLgBeL wER7nQvAYnZ+MLHrBXviPAFkOmCQukqPmo5zHNmBkfaFeyYZbZ7xle/+GUENd5KrvtLO5W6yg n/Ao5EbIP2Go550RLU3CcVMBbM6s3iYNNAMytpi3pW7CanIMi0hNzkTD9z2U9TiygC+NyCzmh 6gZaOPEjdp7hp1dU4LJGRIbDfCpccN+LZGoNR9eAcuqdpBRVRBpVp4ebyxWXrANFzmC/zKMoh blP0smrCw6tib35T9bYUBA8qr2PAkN1lOXgRddh15in54xCyOzbV/RnIpwrDyzM8bGFWaXah1 +s+QVuBpgeBseQD0sKd4a9P3eHM4qBROvp0Szt/0G3LeEaVc1p5JG4ghLxJi1kDYTyaLehCnD hzfLYEcEztD0nMKt3NRpasLN/enuspL9FMH+aSGvmkVT2aK4x9Pw5JjKvzOZo9BUXNWqsvllk KIdHWGAaVPF4ZGm52mXsN1Tly3q4Jms8GnZiNq5rEjQzFNS8thcdg9pCzK7WGIEV090VlUOdw OPO1hNKyeoSFT6z77hviatJGvhQzxn2iHKyVRiCtv4H9wdBtRCbi7Rw6L0cEb3hUgK9K+h62j 1e068Lo2A8c/FVihTDmrYzeAnlgK9SXx5b04PwpcNdUQ9XgOhTtBeCqPTiGXTpj3kYj/U6RLC PLSFUN3X8HSsn7/RLsnxfhunSiMfbmT3dsdeX53NczQ+3+L3TUHhkdn9Use2x/2DuG9gxnl3g AJZ1GYO02hn0HeJ3eVxusr15f9OTLJFLBNcUIUYazmery63zYB+vNHNnZ7fNavy1dfKhGO4fb P7ERAWZMg5T5dkQRIotdGsNWWD6U7vc7kcJB1i+kRQM578vek7Z6CSkHztHGHC4x3nGndezGz Yd3MVSECGc+GbEUS5YEYMZyK8OIkqZ0B2V8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2021-08-02 at 09:02 +0200, Sebastian Andrzej Siewior wrote: > On 2021-08-01 17:14:49 [+0200], Mike Galbraith wrote: > > On Sun, 2021-08-01 at 05:36 +0200, Mike Galbraith wrote: > > > On Fri, 2021-07-30 at 22:49 +0200, Thomas Gleixner wrote: > > > > > > > > > > First symptom is KDE/Plasma's task manager going comatose.=C2=A0= Notice soon > > > > > > > > KDE/Plasma points at the new fangled rtmutex based ww_mutex from > > > > Peter. > > > > > > Seems not.=C2=A0 When booting KVM box with nomodeset, there's exactl= y one > > > early boot ww_mutex lock/unlock, ancient history at the failure poin= t. > > > > As you've probably already surmised given it isn't the ww_mutex bits, > > it's the wake_q bits.=C2=A0 Apply the below, 5.14-rt ceases to fail.= =C2=A0 Take > > perfectly healthy 5.13-rt, apply those bits, and it instantly begins > > failing as 5.14-rt had been. > > Given what you have replied to the locking thread/ > ww_mutex_lock_interruptible() may I assume that the wake_q bits are fine > and it is just the ww_mutex? Nope. Before I even reverted the wake_q bits, I assembled a tree with the ww_mutex changes completely removed to be absolutely certain that they were innocent, and it indeed did retain its lost wakeup woes despite complete loss of newfangled ww_mutex. 5.13-rt acquired those same wakeup woes by receiving ONLY the wake_q bits, and 5.14-rt was cured of those woes by ONLY them being reverted. I'm not seeing the why, but those bits are either the source or the trigger of 5.14-rt lost wakeup woes... they're toxic in some way shape fashion or form. -Mike