From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Cotte-Barrot Date: Mon, 23 Aug 2004 08:29:20 +0000 Subject: Re: [PATCH&RFC 2/2] OS_MCA Recovery from poisoned memory read Message-Id: <4129AAE0.4726DAC8@bull.net> List-Id: References: <41121484.40804@jp.fujitsu.com> In-Reply-To: <41121484.40804@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Hidetoshi Seto wrote: > > Keith Owens wrote: > > mca_handler_bh() is running as an extension of the MCA event which > > means that it is not irq safe. It is not safe to get any external lock > > in mca_page_isolate() or mca_handler_bh(). > > Therefore the MCA handler couldn't recover the system if the process is > running in kernel-mode since it possibly has such important kernel locks. > > > AFAICT, my concerns about the MCA event and mca_handler_bh() not being > > irq safe are only a problem for the case when the MCA was triggered by > > user space code but was delivered when the cpu was in kernel code. > > Maybe we do not support the problem case. > > > > * offending process affected process OS MCA do > > * kernel mode kernel mode down system > > * kernel mode user mode kill the process > > * user mode kernel mode kill the process <== problem > > * user mode user mode kill the process > > So we have to guarantee that the process is running in user-mode, > which all processes can't have any locks of kernel, right? > > It would be happy if this fixed patch satisfy your requirement. > Surprising it looks like a discovery (locking problem within the mca handler) ? Here is Zoltan's document including a design that exposes a solution how to avoid race (paragraphs 3.5, 3.5.1, 3.5.2 ...) and many other stuff : http://mca-recovery.sourceforge.net Linux Itanium MCA Recovery Design Document, third draft http://mca-recovery.sourceforge.net/mca3.html -- +======+============+=================+ | |\/\/\/| | | | | | | |Christian Cotte-Barrot |org. :BULL/ | | | (~)(o) |Bull S.A. |office:FREC/B1-401 | | C _) |1, rue de Provence |mailto: | | | ,___| |B.P. 208 | Christian.Cotte-Barrot@bull.net| | | / |38432 ECHIROLLES CEDEX |phone :+33 (0)476297725 (229 7725)| | /----\ |FRANCE |fax :+33 (0)476297518 (229 7518)| +======+============+=================+