From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 1AFBF4AA1CF; Thu, 15 Oct 2026 07:52:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792050766; cv=none; b=Ry8/5sHTYrTyL6Rr+iGYhFfSbCK0jAw5alBIwS2MaOf2YV03JcFavUonvEzlpW8JQGAhoQLL474Ne2EvRa7sB8l2vru1NoCF/UTh6Wq7wTquJwfF8go433Al3lr7ERA1m/9rofrxdskYKE7R6gHf7zOLQ9c1g37dGEWAOZBHqdM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792050766; c=relaxed/simple; bh=ap9cJcw/BJOApFWzFN+z4P4RITJ2yvuwfW4aPNDU+58=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jNoRTjEWWpATY/RrmxhElNpeiheg6Sz3X5XGhwmTVpqj9I7mMVaoA+g3hpiDq3TY1NaN67QbjufWJrm25Y5oij9KH3Daz54bLyjoK38RiB8Kti9m5fdB865R3Jmwe72Jvkb58SosGUImf20A+b4xTAEM5XbIw6p4zPE+dvfwvf0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=o2JbxUQy; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="o2JbxUQy" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KcDkoczLZtkXZLmEqUsWfJpdm+QFtb7s3+UB08BN4c4=; b=o2JbxUQynwPIsa8krrwXrFIdmF 4RElsF95/oQTSa/WYzPavhCHGYnwpzsg/Zx3PUGfkOAQkAJRAgkCEz2do9kjPhkOEnCbBmFaLUDBz UEclrll02K7dZzjTwni1nJyrlqmGlCDG3D2aA4kfCT06P4oiLXqhm13S/w6vRRLTGUXnuLG82PNk4 GIHj+9A6JPGhGupcY33CPJllHA3bQwVeOelJJ4ckuhlH1tiGxdghJLsG7rO/aK69Ohewuqu6eAyJQ jYKNBzPbyVBs0Z6H67gwaM/O0l0ZeoRSsbd9MDW3/zZfGj0SWoPMfOFuowc05T3Rtna6nB082R+Yo KGfQPBGw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1xHGG3-0000000BteX-3Ak5; Thu, 15 Oct 2026 07:52:11 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 517013006DD; Thu, 15 Oct 2026 09:52:11 +0200 (CEST) Date: Thu, 15 Oct 2026 09:52:11 +0200 From: Peter Zijlstra To: Catalin Marinas Cc: "Christoph Lameter (Ampere)" , Ankur Arora , Haris Okanovic , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, bpf@vger.kernel.org, arnd@arndb.de, will@kernel.org, akpm@linux-foundation.org, mark.rutland@arm.com, ast@kernel.org, rafael@kernel.org, daniel.lezcano@linaro.org, memxor@gmail.com, zhenglifeng1@huawei.com, xueshuai@linux.alibaba.com, rdunlap@infradead.org, david.laight.linux@gmail.com, broonie@kernel.org, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, ashok.bhat@arm.com Subject: Re: [PATCH v15 12/16] cpuidle/poll_state: Wait for need-resched via tif_need_resched_relaxed_wait() Message-ID: <20261015075211.GN2009045@noisy.programming.kicks-ass.net> References: <20260831202251.305046-1-ankur.a.arora@oracle.com> <20260831202251.305046-13-ankur.a.arora@oracle.com> <178908146776.2725577.2613699832033292946.b4-review@b4> <878q58z2ej.fsf@oracle.com> <3e8bda45-0aa7-d0be-8aad-dab95902dcde@gentwo.org> <20261014130306.GK2009045@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Oct 14, 2026 at 04:23:20PM +0100, Catalin Marinas wrote: > On Wed, Oct 14, 2026 at 03:03:06PM +0200, Peter Zijlstra wrote: > > On Wed, Oct 14, 2026 at 10:00:18AM +0100, Catalin Marinas wrote: > > > It > > > would also be nice to get some acks from the atomic infrastructure > > > maintainers. > > > > That'd be Mark and me I suppose. I don't see anything substantial > > happening, just plumbing the new function. > > Thanks! > > > Now, I really rather dislike timeout based schemes, but given we have > > users, I suppose this does improve things. We should however be weary of > > new ones I suppose. > > There's some arm64 precedent in commit ebababcd0372 ("rqspinlock: > Hardcode cond_acquire loops for arm64"). This one went in without any of > the arm64 maintainers' ack and we've since been trying to come up with a > generic interface instead of reverting it. It was fixing a bug where > arm64 smp_cond_load_acquire() does not evaluate cond_expr unless the > pointer is also written by another CPU. Arguably the bug was in the > rqspinlock code for not using a plain cpu_relax() loop. > > Anyway, we had several incarnations of this series, some with a default > timeout but others objected to it (Arnd and Rafael IIRC), hence the > proposal here that pleased most people (not all though ;)). Yeah, I didn't mean to say I'm against this series -- just weary of timeout based schemes in general. So feel tree to pick up this series when it seems ready.