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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F73CC05027 for ; Tue, 14 Feb 2023 20:19:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232011AbjBNUTV (ORCPT ); Tue, 14 Feb 2023 15:19:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229881AbjBNUTR (ORCPT ); Tue, 14 Feb 2023 15:19:17 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C81381CF73; Tue, 14 Feb 2023 12:19:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 68905B81F0C; Tue, 14 Feb 2023 20:19:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40F00C433EF; Tue, 14 Feb 2023 20:19:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1676405952; bh=8/V8zQrKDfVgeKbs27WthihxgwdivBHQ1xvEeA6uoYs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vQOpB4jZU06j0E1MKDDJZEPPNRmXS0/cOAjGFTxoXLPrgQIK/B47hTb0QFcKIneZb s0jPY923NwwG0EAaHw8yq2VeY+rnIZejt5UaWx/A6Novye6lAoPweaDLN/vVDTfV4/ z2wbU080F9o3lsW1XlbaHeONXQOQPrvD/SUfEbdGlUuV0/0zX3LoW10/MVrsarzBdE ceX7Oa5FeZeJLYpScL4JzHvW13XbOGzyYkvzihDtHpZE/AnlwkFrJ1ZK6bjfdTEzD6 0YVc817WUB5hgfgY4gpdM1zFQ3vDBu3uys4X8js6W3ZOQyDxWfawx8vYr8MN57D9M7 IlAUpkSGii2pg== Date: Tue, 14 Feb 2023 12:19:09 -0800 From: Josh Poimboeuf To: Max Filippov Cc: juri.lelli@redhat.com, dalias@libc.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, peterz@infradead.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, x86@kernel.org, jiaxun.yang@flygoat.com, linux-mips@vger.kernel.org, bsegall@google.com, guoren@kernel.org, hpa@zytor.com, sparclinux@vger.kernel.org, kernel@xen0n.name, will@kernel.org, vschneid@redhat.com, f.fainelli@gmail.com, vincent.guittot@linaro.org, ysato@users.sourceforge.jp, chenhuacai@kernel.org, linux@armlinux.org.uk, linux-csky@vger.kernel.org, mingo@redhat.com, bcm-kernel-feedback-list@broadcom.com, mgorman@suse.de, mattst88@gmail.com, linux-xtensa@linux-xtensa.org, paulmck@kernel.org, richard.henderson@linaro.org, npiggin@gmail.com, ink@jurassic.park.msu.ru, rostedt@goodmis.org, loongarch@lists.linux.dev, tglx@linutronix.de, dietmar.eggemann@arm.com, linux-arm-kernel@lists.infradead.org, jgross@suse.com, chris@zankel.net, tsbogend@alpha.franken.de, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , bristot@redhat.com, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, bp@alien8.de, linuxppc-dev@lists.ozlabs.org, davem@davemloft.net Subject: Re: [PATCH v2 19/24] xtensa/cpu: Make sure cpu_die() doesn't return Message-ID: <20230214201909.flqc3g3njnbl5hun@treble> References: <1b4afd82-83cb-0060-7cab-8e16d2e69ff9@linaro.org> <20230214182322.r5tyeowxzloiuh72@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 14, 2023 at 11:48:41AM -0800, Max Filippov wrote: > On Tue, Feb 14, 2023 at 10:23 AM Josh Poimboeuf wrote: > > On Tue, Feb 14, 2023 at 08:55:32AM +0100, Philippe Mathieu-Daudé wrote: > > > Can you update the documentation along? Currently we have: > > > > > > /* > > > * Called from the idle thread for the CPU which has been shutdown. > > > * > > > * Note that we disable IRQs here, but do not re-enable them > > > * before returning to the caller. This is also the behaviour > > > * of the other hotplug-cpu capable cores, so presumably coming > > > * out of idle fixes this. > > > */ > > > > void __ref cpu_die(void) > > { > > idle_task_exit(); > > local_irq_disable(); > > __asm__ __volatile__( > > " movi a2, cpu_restart\n" > > " jx a2\n"); > > > > BUG(); > > } > > > > Hm, not only is the comment wrong, but it seems to be branching to > > cpu_restart? That doesn't seem right at all. > > Perhaps the name is a bit misleading. The CPU that enters 'cpu_restart' > loops there until a call to 'boot_secondary' releases it, after which it goes > to '_startup'. So it is a restart, but not immediate. Ah, I see. That sounds similar to what Xen does. -- Josh