From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv2.iuinc.com (IDENT:qmailr@mailserv2.iuinc.com [206.245.164.55]) by puffin.external.hp.com (8.9.3/8.9.3) with SMTP id KAA26021 for ; Tue, 28 Mar 2000 10:18:19 -0700 From: davisg@Celestica.com To: Philipp Rumpf cc: davisg@Celestica.com, Bas Valkema , parisc-linux@thepuffingroup.com Message-ID: <852568B0.005EEA6A.00@tormta3.tor.cel.com> Date: Tue, 28 Mar 2000 12:16:49 -0500 Subject: Re: [parisc-linux] Couple of questions Mime-Version: 1.0 Content-type: text/plain; charset=us-ascii List-ID: Greetings, Philipp Rumpf wrote: > > Transfer-Of-Control button/switch merely appears to result in a system > > reset, its primary use is to recover from system hang conditions while > > preserving the machine state for later analysis, i.e. where and why was > > the sytem hung. > > > > So, in summary, although TOC on the surface appears to merely 'reset' the > > system, it is capable of much more provided the OS specifies an OS_TOC > > entry point for recovery and debug of machine state at any point during > > system run time. > > Actually, that's exactly what reset does on (most) x86 boxes. Remember > getting 286s out of protected mode by resetting them ? > Oh yeah - I vaguely recall this. Painful, ugly and slow. > > I'm not convinced having customized TOC / HPMC handlers for Linux/PA-RISC > is a good idea yet. Agreed! It's a lot of effort to add support for this. Looking back over the parisc-linux archives, the alternative is to use the platform firmware 'pim [hpmc|toc]' command to retrieve the machine state at the time of crash/hang and use this information to manually glark the vmlinux image to see where you were at the time. Although there is limited information to understand the overall machine context at time of crash/hang, there's generally enough information available from PIM to find out where you were (assuming you were even in the kernel at the time). BTW, there is a reference in the parisc-linux archives to trap handlers in the Utah code, Mach I presume, which may be useful as a model upon which to base HPMC/TOC handlers in Linux for PA-RISC. Maybe someday... Regards, Geoge G. Davis Software Engineer, Celestica Chelmsford Design Center 20 Alpha Road Chelmsford, MA 01824