From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx163.postini.com [74.125.245.163]) by kanga.kvack.org (Postfix) with SMTP id 289EF6B004A for ; Tue, 13 Mar 2012 02:00:52 -0400 (EDT) Received: by vcbfk14 with SMTP id fk14so320159vcb.14 for ; Mon, 12 Mar 2012 23:00:51 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20120312.225302.488696931454771146.davem@davemloft.net> References: <1331617001-20906-1-git-send-email-apenwarr@gmail.com> <20120312.225302.488696931454771146.davem@davemloft.net> From: Avery Pennarun Date: Tue, 13 Mar 2012 02:00:30 -0400 Message-ID: Subject: Re: [PATCH 0/5] Persist printk buffer across reboots. Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: David Miller Cc: akpm@linux-foundation.org, josh@joshtriplett.org, paulmck@linux.vnet.ibm.com, mingo@elte.hu, a.p.zijlstra@chello.nl, fdinitto@redhat.com, hannes@cmpxchg.org, olaf@aepfle.de, paul.gortmaker@windriver.com, tj@kernel.org, hpa@linux.intel.com, yinghai@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, Mar 13, 2012 at 1:53 AM, David Miller wrote: > From: Avery Pennarun > Date: Tue, 13 Mar 2012 01:36:36 -0400 > >> The last patch in this series implements a new CONFIG_PRINTK_PERSIST opt= ion >> that, when enabled, puts the printk buffer in a well-defined memory loca= tion >> so that we can keep appending to it after a reboot. =A0The upshot is tha= t, >> even after a kernel panic or non-panic hard lockup, on the next boot >> userspace will be able to grab the kernel messages leading up to it. =A0= It >> could then upload the messages to a server (for example) to keep crash >> statistics. > > On some platforms there are formal ways to reserve areas of memory > such that the bootup firmware will know to not touch it on soft resets > no matter what. =A0For example, on Sparc there are OpenFirmware calls to > set aside such an area of soft-reset preserved memory. > > I think some formal agreement with the system firmware is a lot better > when available, and should be explicitly accomodated in these changes > so that those of us with such facilities can very easily hook it up. Sounds good to me. Do you have any pointers? Just use an early_param? If we see the early_param but we can't reserve the requested address, should we fall back to probing or disable the PRINTK_PERSIST mode entirely? Thanks, Avery -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org