Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751826Ab2EHJV3 (ORCPT ); Tue, 8 May 2012 05:21:29 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:40881 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751149Ab2EHJV2 (ORCPT ); Tue, 8 May 2012 05:21:28 -0400 Date: Tue, 8 May 2012 10:21:09 +0100 From: Will Deacon To: Colin Cross Cc: "linux-arm-kernel@lists.infradead.org" , Russell King , Marc Zyngier , Catalin Marinas , Thomas Gleixner , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] ARM: SMP: prevent use of the console when using idmap_pgd Message-ID: <20120508092109.GB2263@mudshark.cambridge.arm.com> References: <1336180444-26563-1-git-send-email-ccross@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1336180444-26563-1-git-send-email-ccross@android.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 34 Hi Colin, Sorry for the delayed response. On Sat, May 05, 2012 at 02:14:02AM +0100, Colin Cross wrote: > Commit 4e8ee7de227e3ab9a72040b448ad728c5428a042 (ARM: SMP: use > idmap_pgd for mapping MMU enable during secondary booting) > switched secondary boot to use idmap_pgd, which is initialized > during early_initcall, instead of a page table initialized during > __cpu_up. This causes idmap_pgd to contain the static mappings > but be missing all dynamic mappings. > > If a console is registered that creates a dynamic mapping, the > printk in secondary_start_kernel will trigger a data abort on > the missing mapping before the exception handlers have been > initialized, leading to a hang. Initial boot is not affected > because no consoles have been registered, and resume is usually > not affected because the offending console is suspended. > Onlining a cpu with hotplug triggers the problem. > > A workaround is to the printk in secondary_start_kernel until > after the page tables have been switched back to init_mm. You missed a word out here (`delay'?) but it looks like Russell has taken this now so I'm sure we'll cope. Acked-by: Will Deacon Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/