From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Getz Subject: Kernel crashing and log buffers... Date: Wed, 10 Jun 2009 21:26:40 -0400 Message-ID: <200906102126.40410.rgetz@blackfin.uclinux.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline Sender: linux-embedded-owner@vger.kernel.org List-ID: To: Mike Frysinger , Greg Ungerer , Russell King , Paul Mundt , Tim Bird , Wolfgan Cc: linux-embedded On 17 Oct 2007, after much discussion and debate, Mike added add two new functions for reading the kernel log buffer (from kernel space). http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=0b15d04af3dd996035d8fa81fc849d049171f9c3 The intention was for them to be used by recovery/dump/debug code so the kernel log can be easily retrieved/parsed by the bootloader (or another kernel) in a crash scenario. I was going to push the arch specific recovery/dump/debug code that uses them upstream (yeah, it has been a little while - but anyway...) it was removed since then by Roel Kluin ... 21 Oct 2008: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=acff181d3574244e651913df77332e897b88bff4 Before I ask Andrew to add it back, I thought I would make sure it was still a useful function, and did everything everyone wanted - and wasn't deemed unnecessary by a feature/function that I wasn't aware of - like the next thing... I saw the patch Grant sent recently - Add Alternative Log Buffer Support for printk Messages (in Nov2008 to the embedded list, and Jan 2009 to lkml) - but I couldn't find any followups - and it doesn't seem to be in Linus's tree. http://thread.gmane.org/gmane.linux.kernel.embedded/1358/focus=1373 http://lkml.org/lkml/2009/1/21/250 I can see the desire on Wolfgang & Grant's part - for not needing the copy from/to - (you never have to worry about crashing "nicely" - the kernel panics, but you still need to copy memory around - potentially causing all kinds of secondary issues - and masking the real reason the crash occurred). But for the majority of the case - the copy from/to would work much better than what we have in mainstream today... I would be interested in Paul and Russell - how have you solved this issue? (Or do your kernel's never crash? :) Thanks -Robin