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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E3E1C25B75 for ; Wed, 29 May 2024 10:34:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9D61D6B00AC; Wed, 29 May 2024 06:34:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 986F56B00AF; Wed, 29 May 2024 06:34:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 84D676B00B0; Wed, 29 May 2024 06:34:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 671076B00AC for ; Wed, 29 May 2024 06:34:17 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0EDEE1A09E5 for ; Wed, 29 May 2024 10:34:17 +0000 (UTC) X-FDA: 82171073754.30.E7A5AF6 Received: from mail-wr1-f54.google.com (mail-wr1-f54.google.com [209.85.221.54]) by imf16.hostedemail.com (Postfix) with ESMTP id 156BC18002E for ; Wed, 29 May 2024 10:34:14 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=layalina-io.20230601.gappssmtp.com header.s=20230601 header.b=Tc1f3+Xv; spf=pass (imf16.hostedemail.com: domain of qyousef@layalina.io designates 209.85.221.54 as permitted sender) smtp.mailfrom=qyousef@layalina.io; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1716978855; a=rsa-sha256; cv=none; b=m0NdUhkWJ2lT9hdwpwtcaCvYCkC00qp7f8e1HBtvco0muXkZSdDd/qXVzL09COh9n9uqBS qOBgjDu8Vc5/X6JR0eg+7lIEwlpsy7lG/NrwN+tGY8FrNaGa5h5+wHNtcRFomCwHFaC+mJ BOhT1XoyALhbMtZwiSa9KfZln5fXEIM= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=layalina-io.20230601.gappssmtp.com header.s=20230601 header.b=Tc1f3+Xv; spf=pass (imf16.hostedemail.com: domain of qyousef@layalina.io designates 209.85.221.54 as permitted sender) smtp.mailfrom=qyousef@layalina.io; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1716978855; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pWxQqhsuf8BC7pPkaTLgrKW/tD/H2B+jRA3s0q6FfWo=; b=MfKYoGXEFh+BQ9uxzAFyW6nMtMO/fmnDHlZ+Ry7IVQLWbanYugVVMRxGs4edvEHON4V/l5 OLQh7132q0fNUVC8tadO9NRIV1RnihOCxtwGk8qU7vDFKsPJhykCG/+/CNB0R8btAvBgwK aXOlhUEL4YpUE26gtgZV3sWMsx7FL/k= Received: by mail-wr1-f54.google.com with SMTP id ffacd0b85a97d-3588cb76276so399302f8f.0 for ; Wed, 29 May 2024 03:34:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=layalina-io.20230601.gappssmtp.com; s=20230601; t=1716978853; x=1717583653; darn=kvack.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=pWxQqhsuf8BC7pPkaTLgrKW/tD/H2B+jRA3s0q6FfWo=; b=Tc1f3+XvQMWsOGKZri/vPZ3Z5IOP4xQMf1DatZ2zF4cws218CxQX+ciGlymeEwHdBx zDlmiArOVnlknMNCw2UYouJx6ULn5+nhyMm5zSsNthNx+59GOyFJav2iqQZxDjCgoc7j IJG3rG4uAU1dcCStU0Nr25IpYR1nusP9GeHjIjciUWHuyAU/8f/aA3EU+MS0QW1hVyAh i/655fua7jPUG5K9gxXtJgHm/nUBcPiZI2KPy/1UuOgOjCO83PX5ePv9VIa9sSeNrCoY vOSDdrwWrItgT82ZYK3KBPTuHbnrbahSlNpC/19pACw5jyMNY+OSvxpiR3XXgo0tpqss cLSA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1716978853; x=1717583653; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=pWxQqhsuf8BC7pPkaTLgrKW/tD/H2B+jRA3s0q6FfWo=; b=lNd/v30LvrvbivlOlp5VDA1DwfkDIRkjpZOztuvUZ1dIcbiEr81do68aIcUKSVk0Fn AI3vO+Rab/5clERCLYeWZzdvwvKRab6qnzBoDf3pDXp3OR1wNJWefM3A+NGSlO1GeMfn aDJEQjrQAmFhYhcanImyGzR3/+c+V3SBPcCxKY3+rlXKeEC3d+oTLVB8EjYvuRw6tEOu TleRlhoxcXtio+lzYuSzxKNgtHRnzljocaLKCso/8Zyzg7ZOn9UUke8oqE2YQR4km47W qKorXr8rmAUBmDGUJE6kUH7nZz1mPKDVKCkVtDD7Kx4uo9xhADgX1T743Lyeft5k8Dzp kSZA== X-Forwarded-Encrypted: i=1; AJvYcCVk/v1HFSXQONSDUMZ1SpC/EWtUpSxNGeXxSnXhHAsmIK+0gnrozEBhzsXketpWgBCaTKnge4R6qdT1pMK1Pw1GuFo= X-Gm-Message-State: AOJu0Ywanj3LOEmPrGxDTxpaJQ60L/UlOyz/LNbX4mqdFT50byUaXTpH Z61GJsWB1O5jBfr4atBpFM9r6/QjxY75ldMhCQp5LbQkIm++XLLsnpKl5zGLtlU= X-Google-Smtp-Source: AGHT+IGSszxrKbHSyGgQ7mAClIEtVdH7p9Lx2JOJh6npifDBZVn+xxJ8yW2MTf6yCWOUozN0vx/rZg== X-Received: by 2002:a5d:4602:0:b0:34c:fd92:3359 with SMTP id ffacd0b85a97d-35c7af09709mr1539637f8f.21.1716978853406; Wed, 29 May 2024 03:34:13 -0700 (PDT) Received: from airbuntu (host81-157-90-255.range81-157.btcentralplus.com. [81.157.90.255]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3557a1c92f8sm14306730f8f.67.2024.05.29.03.34.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 May 2024 03:34:13 -0700 (PDT) Date: Wed, 29 May 2024 11:34:09 +0100 From: Qais Yousef To: Sebastian Andrzej Siewior Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Steven Rostedt , Vincent Guittot , Daniel Bristot de Oliveira , Thomas Gleixner , Alexander Viro , Christian Brauner , Andrew Morton , Jens Axboe , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, Phil Auld Subject: Re: [PATCH v2] sched/rt: Clean up usage of rt_task() Message-ID: <20240529103409.3iiemroaavv5lh2p@airbuntu> References: <20240515220536.823145-1-qyousef@layalina.io> <20240521110035.KRIwllGe@linutronix.de> <20240527172650.kieptfl3zhyljkzx@airbuntu> <20240529082912.gPDpgVy3@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240529082912.gPDpgVy3@linutronix.de> X-Rspamd-Queue-Id: 156BC18002E X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: tndr99rz89fxrqihg3hgpda7wfw8s51s X-HE-Tag: 1716978854-52365 X-HE-Meta: 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 Gw7AWaKJ Y7NuNcuSa7I6dtuDHDhCTD9dTTXerSHucyA5UKhYifMdq4RUi7HPFOYQOkrn4ufjWH1wHUr7v8Da+lshAygVnsiCnUc54gerzAuNiFxTRpe0A5grBC9xF699ecj2F4SDagvOCbC+iDsC2CpT0yHQDxGmhFIh4J+0iFeR9SBeFP0Af0ZFveSuvoppYULawthucA5ixkyfFlP7vaGY92z6HkCh7WZUH9vEKMVP1fUS8LJ7d2W3UDxeGlxwuvsrvqM5QYFH4j9h3g3lQkWicejwycfKO9VlRDPndm0iU20C1GAzSViHDRHj4GvPnsvw+Mj7Djo4BlkU12+NaWX0Y0KS6c1BQVs7J2UqnjbtVj9M6zgOkGg4wQe/7HLIX/4S417rI1g905A/UC7BFJv34nyLUTs6QuREwpfPvMSjqxoDSW2UGCRlcXsCGwcC3crt5V1WJz4QOuoCkK6uGXmOcYMMxC2WfoQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.003514, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 05/29/24 10:29, Sebastian Andrzej Siewior wrote: > On 2024-05-27 18:26:50 [+0100], Qais Yousef wrote: > > > In order to be PI-boosted you need to acquire a lock and the only lock > > > you can sleep while acquired without generating a warning is a mutex_t > > > (or equivalent sleeping lock) on PREEMPT_RT. > > > > Note we care about the behavior for !PREEMPT_RT. PI issues are important there > > too. I assume the fact the PREEMPT_RT changes the locks behavior is what you're > > referring to here and not applicable to normal case. > > So for !PREEMPT_RT you need a rtmutex for PI. RCU and i2c is using it > within the kernel and this shouldn't go via the `slack' API. > > The FUTEX API on the other hand is a different story and it might > matter. So you have one task running SCHED_OTHER and acquiring a lock in > userspace (pthread_mutex_t, PTHREAD_PRIO_INHERIT). Another task running > at SCHED_FIFO/ RR/ DL would also acquire that lock, block on it and > then inherit its priority. > This is the point where the former task has a different policy vs > priority considering PI-boosting. You could argue that the task > shouldn't sleep or invoke anything possible sleeping with a timeout > 0 > because it is using an important lock. > But then it is userland and has the freedom to do whatever it wants you > know… Yes.. > > So it might be better to forget what I said and keeping the current Okay I'll drop the patch then in next posting. > behaviour. But then it is insistent which matters only in the RT case. > Puh. Any sched folks regarding policy? I am not sure I understood you here. Could you rephrase please?