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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 760FFCC6B1A for ; Wed, 14 Oct 2026 15:23:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=6aZmQ10b0wpN+iMg2EPUIHXrTZZaaV+5qOQVOwN9O4k=; b=XjSFw0jOnedBl8ByzwuwT2LRaa wjPfJQSKCAzr4a4amP2UGDFVu9d3maAplQWyV1oj9ChPQVsodMejlZZUhqLLO2CRzVY172i14MCkX F/UsZp0EIeGSYCMvWncjbpdYN216wIlTCaaJCrmofqewjzTi66cKzHZKL2WIs56nUgpii/1DYTvyp RXQL1kmiYDoQTEsau01uW6p8QlM6y/2DFAaySruito56B28/I6QsfPDwvj3TkX2tIK9OcoI04BkCz a6MidNhWcNYphnRBl5jZ23OpPYDIhHjWiUCOvTerfFfez0ZHKmBhbHAZCsIfCqwkE17PFEWg1MEhV Zwcbe5+Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xH0pP-0000000Fq2F-3Qpy; Wed, 14 Oct 2026 15:23:39 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xH0pH-0000000Fq0U-0TYM for linux-arm-kernel@lists.infradead.org; Wed, 14 Oct 2026 15:23:38 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DF9B61570; Wed, 14 Oct 2026 08:23:21 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 32C683F7B4; Wed, 14 Oct 2026 08:23:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1791991405; bh=1DLWRMbZyOAA0rVioqQfDUzvKGaVa837pvjO2TrdaZE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BiwEjp9uaNUxIi5ciO5EDAG5qEO3ENWk/lYMARr7Uggqz/ut2q3CTw8kTspOFi1zo lHQZGmwZP0ZENsvMT+FmZV5rbyvIcKrLhkmCA8C0J04SvgcNDM5XXlrPenFvd6Mrkj BUk3lDOPxmpqk7uJw7yqDFTdYVgi5JOvXJrteTiw= Date: Wed, 14 Oct 2026 16:23:20 +0100 From: Catalin Marinas To: Peter Zijlstra 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: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261014130306.GK2009045@noisy.programming.kicks-ass.net> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261014_082337_060686_9AB545CB X-CRM114-Status: GOOD ( 13.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 ;)). -- Catalin