Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!rochester!uhura.cc.rochester.edu!ur-valhalla!micropen!dave
From: dave@micropen (David F. Carlson)
Newsgroups: comp.unix.wizards
Subject: Re: Ultrix tape job is unkillable!
Summary: periodic postings
Keywords: ultrix tapes
Message-ID: <594@micropen>
Date: 20 Dec 88 14:03:24 GMT
References: <476@larry.UUCP> <732@auspex.UUCP>
Organization: Micropen Dirent Writing Systems, Pittsford, NY
Lines: 27

In article <732@auspex.UUCP>, guy@auspex.UUCP (Guy Harris) writes:
> >Now (besides the obvious, cntl/C to the program), what do I
> >do in the future when we have such a hung process?
> 
> Reboot.  I suspect the problem may be that an interrupt was lost, or
> since it's waiting at a priority less than PZERO, you can't get rid of
> 
> In this particular case, there is arguably a bug in the tape driver; I
> don't know how easy it is to fix. 

Of course, there is a bug.  And by the description, the driver is waiting
at less than PZERO too.

My suggestion, and yes, in my code requirements, is that *ALL* device drivers
have a hard reset ioctl that frees every used resource and resets the state
of the hardware to a known good state.  There is no excuse for the default
action of a driver bug (yes, there will be bugs) hanging a process without
any hope of salvation.  The code is usually already written in for most drivers
that have an init() code.

Is there any reason to build a device driver without a hard reset?

-- 
David F. Carlson, Micropen, Inc.
micropen!dave@ee.rochester.edu

"The faster I go, the behinder I get." --Lewis Carroll