From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=193.142.43.55 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793907014; b=Ro0qCVcpXVd9WCyD9GMQJzua9hw75gHre+VM32jOAuVNXJchJodWFUDD8EvNmtbgu4rO W+dWYpIXISvKSJL9h1R2KU2cHqu+m4OQiKNFQacgb/9GrTe7kyoZyqF3QjlIPA0y5AGT6 dMs80Dhr06Akd9gEUo8poZEK/667wqRGrYdTgvw6bl8Fm0VpUQgHuI6IMIrf4J+RlxeoG 9hbBllHADULa8dOfHMy03L3CYTY5Mt7xVcq6+QnQUO8LHuvHHYpa+bN/a46yDZGjUuLro DM+paSZILxauB1R9cYuRQti9A43xIwky3huNFBQvPGlHPKcANprDRtIR0qQypN6l5mw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793907014; h=DMARC-Filter:Date:DKIM-Signature:DKIM-Signature:From:To:Cc:Subject: Message-ID:References:MIME-Version:Content-Type:Content-Disposition: In-Reply-To; bh=hBiMPC/mSRFQIthZJMHQ6VsuWvW84Hflt7MDyKrRRhE=; b=A2wnZQ93neSM2VcuVvn4ze8ftQ/fghJcQ0B4ygxAdH6GFP8Xt658XtbBU1GVsWslMJu/ /SKiHYYr3ptTRiW/vVyqGkoaPlCbrFUsKlIEsG3k1lQbs2GChtxBbPmcWaq3fdaUDTj2y Yo0yoFTpUB1SNwmb6CJBARJUzoYTT/OrrCSbRCWgQ+emqwdzpIKhGW1rEfsWuPJ/XemMl PJChJ2uHGbjMjsv4ZuSEVjRgo98VlQIfT+t24WbMXL9V7DaJUP/Ko78v7ckwuk/0WLrGm mDhA1WY1CraztKx/vIQgDWZjFlmeR8D1S2u22Nq1CkK/y1lyxe375aNYfpc/8SrEGhg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=rsa-sha256 header.s=2020 header.b=ONzyxZ09; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=ed25519-sha256 header.s=2020e header.b="q/7HWdtA"; arc=none smtp.remote-ip=193.142.43.55 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53FAC606A6EE; Thu, 5 Nov 2026 19:30:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 53FAC606A6EE Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=linutronix.de header.i=@linutronix.de header.a=rsa-sha256 header.s=2020 header.b=ONzyxZ09; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=ed25519-sha256 header.s=2020e header.b=q/7HWdtA Date: Thu, 5 Nov 2026 20:30:10 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1793907012; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hBiMPC/mSRFQIthZJMHQ6VsuWvW84Hflt7MDyKrRRhE=; b=ONzyxZ09QiqxpgqKgkhY8CcKeGquIrSofRjgsorpQfVlVsIu+2bx4JA9aPix/aklhiwYNI NtrpnYDNDMoc3g79qGlohNhpS7TtZdw8bFDmSDkjDEj58o2dJA43aES2tdctXdDvGueGwN 14q4oarYSEWkYznum0vCnKhzyc14yI2Y2LNRwtp/J2Jj7RsDjrVIsundKyVDEKPl6zlcT/ uzc1UXtj7/31BZBx/3fZyhizPNl0tANNetAxsiR8JQhvmHCc4g5BCdti2RObgCvgq8db+X 9s2wGtXUWd1F17oUB7fg+Ix10AvHZm/FiqjL7JmOt7Q5nz6BJi533VUBQaUgRQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1793907012; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hBiMPC/mSRFQIthZJMHQ6VsuWvW84Hflt7MDyKrRRhE=; b=q/7HWdtAJhzMMCC8FYyQrmjg3F9P1Q8m/5sbtDH5MXzrNIYZB76HbsTvd7nfWL9xxJKrM8 ueNzLPNDTkTmw/Cg== From: Sebastian Andrzej Siewior To: Tejun Heo Cc: linux-rt-devel@lists.linux.dev, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , K Prateek Nayak , Johannes Weiner , Michal =?utf-8?Q?Koutn=C3=BD?= , John Ogness , Shrikanth Hegde , luca abeni , Yuri Andriaccio , Yuri Andriaccio Subject: Re: [PATCH] sched: Remove CONFIG_RT_GROUP_SCHED Message-ID: <20261105193010.tXUDDu2w@linutronix.de> References: <20261105164724.yxONBd03@linutronix.de> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On 2026-11-05 07:19:27 [-1000], Tejun Heo wrote: > Hello, Sebastian. Hi Tejun, > > I'm not against it but wonder whether it'd be useful to do it more gradually > so that people can pipe up if they depend on it. ie. Mark it deprecated and > put it behind EXPORT for a bit and then BROKEN before actual removal. I would be surprised if this is actually used especially since it is cg-v1 and v2 is the default/ used by everyone (?). This depended on !PREEMPT_RT in the RT queue. People asked if this can be enabled because it looked useful/ for their use case. I researched why it was like this and dropped that restriction. People then asked if it is broken on RT because it is now working properly. I have never been told _what_ is broken or *why* because nobody came back. Later I've been told (there was an attempt to explain it to me, it was late in the morning) and if I piece it properly together then, it could work in UP environment but on SMP the accounting is wrong and therefore the runtime/ preemption is not working as it should. I didn't add this to the commit description because I would classify this as hearsay and we do facts here. PeterZ might know more. >From what I know, people who asked for it either have a different solution or eyeball HCBS. > Thanks. Sebastian