Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936990Ab3DJPzj (ORCPT ); Wed, 10 Apr 2013 11:55:39 -0400 Received: from mail-qa0-f46.google.com ([209.85.216.46]:56407 "EHLO mail-qa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935973Ab3DJPzi (ORCPT ); Wed, 10 Apr 2013 11:55:38 -0400 Message-ID: <51658B77.4050400@gmail.com> Date: Wed, 10 Apr 2013 10:55:35 -0500 From: Rob Herring User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Colin Cross CC: lkml , "linux-arm-kernel@lists.infradead.org" , Rob Herring , Anton Vorontsov , Kees Cook , Tony Luck Subject: Re: [RFC PATCH 3/3] pstore/ram: avoid atomic accesses for ioremapped regions References: <1365563297-12480-1-git-send-email-robherring2@gmail.com> <1365563297-12480-3-git-send-email-robherring2@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1221 Lines: 26 On 04/09/2013 11:10 PM, Colin Cross wrote: > On Tue, Apr 9, 2013 at 8:08 PM, Rob Herring wrote: >> From: Rob Herring >> >> For persistent RAM outside of main memory, the memory may have limitations >> on supported accesses. For internal RAM on highbank platform exclusive >> accesses are not supported and will hang the system. So atomic_cmpxchg >> cannot be used. This commit uses spinlock protection for buffer size and >> start updates on ioremapped regions instead. > > I used atomics in persistent_ram to support persistent ftrace, which > now exists as PSTORE_FTRACE. At some point during development I had > trouble with recursive tracing causing an infinite loop, so you may > want to test that calling out to spinlock functions with PSTORE_FTRACE > turned on and enabled doesn't cause a problem. I've tested that now and it appears to work fine. Was there some specific setup of ftrace that caused problems? Rob -- 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/