From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ABA421DED58 for ; Fri, 7 Feb 2025 11:00:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738926058; cv=none; b=VKZorzzwdhunlMigDxMJ8L5MQItqSBRCWJV8BhBRBCNEM4kg7HAamknF21wSGWmcrHYWFfS92WmeuxxwTHFqADDKscvmdHL3mNabUyQ4zbye3jJDM3Xj8vuAjExTGkT269ijT5J7aq8o0ntuosDnpfIwd34n5llv1m3BxANCvko= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738926058; c=relaxed/simple; bh=ND6hyoxlDXntD4lr9CxXkDZB0S8XhihlSQSUomBwZ8o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YjpFtv9H+fCf1Nz/42pWJoy8r48wg7ION8F1nsW7eMg4ybicBUObe6OnxpGoJiSWn2XinF/qhN1TaZk3pG4/147OQgUZSEvamwiXKL4b+mOabl0pikt2AduIcEW2QiARvWu6tFsDqalYGAVLcCiVQd2o5yGV62os9QNgyp0oLZY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=f2LYInOT; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=RaqhgcBu; arc=none smtp.client-ip=193.142.43.55 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) header.d=linutronix.de header.i=@linutronix.de header.b="f2LYInOT"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="RaqhgcBu" Date: Fri, 7 Feb 2025 12:00:50 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1738926052; 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=vfsUlhtHiJhl83lKMUrwmrR3sEtm/wa5PfIaal738eA=; b=f2LYInOTB6R3wqsY6FyVjt0McjVzSZ+yWUffvyYWQtNNeW7rX0KCBm4i7oLJvJ6UAm4adM musuInJiae5FkiIxmd+YLvkhl8enAqFvKuFaZLpJ5hdz7MltuVcnoWyZmAFX2GuZCt6GeQ csD0sEDPr+CKCyyNk2VjyTG2dMxljpdX7/ZTLbdLc4wYkdGsKiHeHsp5J1J/NPoaZslrKc 8GQWnbU8YZJS2bnD/nXs6kt/ojqwygUJedz999IT+RF0MmPsFrb1fZbtX1xAJVPmph53Vn VMp1P14b12hIa91BoHwlDRs6QaDkp/api74D8F565LlF58XAXp+hmVchNhTDpA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1738926052; 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=vfsUlhtHiJhl83lKMUrwmrR3sEtm/wa5PfIaal738eA=; b=RaqhgcBuIMKrPI9h/hTz3YEKeTwItGQ4SobbA0GHw/p4N2hR4HngXRKO7ALXpJcBtWT4fz BLkCOlg2x6ll9QBw== From: Sebastian Andrzej Siewior To: Juri Lelli Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, =?utf-8?B?QW5kcsOp?= Almeida , Darren Hart , Davidlohr Bueso , Ingo Molnar , Thomas Gleixner , Valentin Schneider , Waiman Long Subject: Re: [PATCH v8 03/15] futex: Add basic infrastructure for local task local hash. Message-ID: <20250207110050.stt_l7KT@linutronix.de> References: <20250203135935.440018-1-bigeasy@linutronix.de> <20250203135935.440018-4-bigeasy@linutronix.de> <20250203142743.GI7145@noisy.programming.kicks-ass.net> <20250203155114.YVGnCHUT@linutronix.de> <20250204103447.GU7145@noisy.programming.kicks-ass.net> <20250205083926.etxnZAoP@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On 2025-02-07 10:41:02 [+0100], Juri Lelli wrote: > Hi, > > On 05/02/25 09:39, Sebastian Andrzej Siewior wrote: > > On 2025-02-04 11:34:47 [+0100], Peter Zijlstra wrote: > > ... > > > > Anyway, none of this solves anything when a process has both an active > > > RT part and an active !RT part (which isn't uncommon AFAICT). > > > > > > Then the RT bits will still get interference from the !RT bits. Do we > > > want to complicate things and consider that? > > > > I don't think so. The active and inactive are common but it is still the > > same process so you can expect it. The ugly part is when it is an > > entirely different task and it is random which one it is. > > Not entirely sure we are thinking about the same situation, but it looks > like we have cases of RT tasks that are affected by the underlying issue > this set is about because they make use of libraries. So, in this case > we have a cross-process (RT/!RT) situation that I am not sure we can > address sanely. What do you think? I wouldn't advice to use "unknown" code in a RT application and even threads. Audit libs before using them and not just collect them. A lock without PI in your RT thread is not good. A lot of locks, not knowing the "locked" time, also not good. Things that work most of the time due to the fastpath and only break from time to time. Also, a thread does fork() once during start up and things may continue to be good but may catch up eventually. > Thanks, > Juri Sebastian