Date: Tue, 4 Feb 1997 05:24:34 -0500 (EST) From: Peter Dufault <dufault@hda.com> To: bartol@salk.edu (Tom Bartol) Cc: current@FreeBSD.ORG Subject: Re: SCSI_FREEZE kernel option? Message-ID: <199702041024.FAA20953@hda.hda.com> In-Reply-To: <Pine.BSF.3.95.970203165443.13561C-100000@pauling.salk.edu> from Tom Bartol at "Feb 3, 97 05:07:53 pm"
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> > Hi, > > I was just looking at the manpage for scsi (8) and was particularly > intrigued by the -z option which claims to be able to freeze the scsi bus > for an audible "beep" delimited (with the -v option) specified period of > time provided you have compiled your kernel with the "SCSI_FREEZE" option. > The manpage goes on to state that this kernel code is not committed yet > and indeed a grep of the kernel source for -current for the string > "SCSI_FREEZE" comes up empty-handed. I presume that an appropriately > contrived sequence of scsi -z and scsi -p commands could be used to > perform hot-swapping of scsi devices -- something I would dearly love to > be able to do. Does this actually work yet and how should I specify any > required kernel options? It isn't in there - I had a code collision with (I think) David Greenman and never put it back in since I was no longer active on that project. Mea culpa. The code he put in should make it easy to add back. It had to do with when you can sleep when submitting a command. I set a flag getting everyone to sleep (probably somewhere around scsicmd) if someone was freezing the bus until no one was active and then froze and thawed the bus. To get around the problem of accessing the bus while frozen it was a "pulse" freeze for a given time. I built the world with the bus freezing every five seconds. This is probably three years back now. I can dig up the code but it is probably easier to do over from scratch. -- Peter Dufault (dufault@hda.com) Realtime Machine Control and Simulation HD Associates, Inc. Voice: 508 433 6936
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