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 B9C89CA601D for ; Fri, 9 Oct 2026 11:07:51 +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-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jFmWCi2up5vRqSBkWFUwHEbyNXCZg+vH8tf6YUwRZ+E=; b=gAHiWygxoTLrdrI17wJbHsQc8Y IbKe0JqmWdRVkZ26tlARv4rOeMKxxZcIYkkM1wDqgR4tzD0+WSDkEbdUMOmTJzfol/MALB45C9tye Kb9EemEOhVVHAH86yNw14Zm+wUxcmDPsW/ijXmNyIKPLPwbjij8cMIXnIfTFXWGKE4n8pHazH8WoI YHGXNM0qD5ZGkDauWHKmt7SoTtn9Vuoo9SJGCWq15LEV7LHKy3JZje/P8d/1Gse40BfUYG8CdDQhU GevrhJrqLKV2+jgiT44Y8l4nllAEE35uu8eon9b6PUXr1yrqE5jD3JhO1lpok8qUaCUFziLNTpBZ5 On9D/Rxw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xF8Rx-000000068Y0-1wpv; Fri, 09 Oct 2026 11:07:41 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xF8Rv-000000068Xb-2EjT for linux-arm-kernel@lists.infradead.org; Fri, 09 Oct 2026 11:07:39 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id F100C60DC2; Fri, 9 Oct 2026 11:07:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9C001F000FF; Fri, 9 Oct 2026 11:07:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791544058; bh=jFmWCi2up5vRqSBkWFUwHEbyNXCZg+vH8tf6YUwRZ+E=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=gDU7cn51regFtSN9oMtRGZ+jprWSuvIKY6x1hSlPtwFlZjPUaI0yz40uNMQ2Wfjmz VKZ9L64iEdFIoz0eox0QqJHZArTjAyNmW8QvxbwltRlrD5ZbUhbQdmZjR69ZeQhNAC /gktJFy7HflqRMbMKAzYPxrpjvmxvX+QXHdjDvYNqwllodgsnUnUVPEH12AMnvWvr3 DwyCRHB07y7AKTVBo69yRYaKYvXGCtx/K35pVUGy4rvkBaTwhc3ykCzy5U4f8/gkjp lnyB9vAKqt4lddMVYU6bh1idXculVyd4O8liGKAb7UQc8HEUutsbymVo4LAX4Afhza vtoAiB05RaayA== Date: Fri, 9 Oct 2026 12:07:32 +0100 From: Will Deacon To: David Woodhouse Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ben Horgan , =?utf-8?B?yJh0ZWZhbmlh?= Ion , Catalin Marinas , Pankaj Patil , Borislav Petkov , Lorenzo Pieralisi , Jinjie Ruan , Mark Rutland , Tarun Sahu , Fuad Tabba , Peter Zijlstra , Marc Zyngier Subject: Re: [PATCH v2 03/23] cpu/hotplug: Avoid busy-polling on archs where cpu_relax() is a no-op Message-ID: References: <20261009100738.31288-1-will@kernel.org> <20261009100738.31288-4-will@kernel.org> <7ba9bf65e714a17657252a7fb267928f8215bc06.camel@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7ba9bf65e714a17657252a7fb267928f8215bc06.camel@infradead.org> 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 Fri, Oct 09, 2026 at 11:46:11AM +0100, David Woodhouse wrote: > On Fri, 2026-10-09 at 11:07 +0100, Will Deacon wrote: > > Change cpuhp_ap_sync_alive() to poll using atomic_cond_read_relaxed() > > relaxed. > > ... > > > +       atomic_cond_read_acquire(st, VAL == SYNC_STATE_SHOULD_ONLINE); > > acquire. Oops, I'll fix the commit message. Thanks. I think we need acquire semantics here so that the AP sees anything published by the BP prior to advancing the state. Will