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From: andrew@frip.WV.TEK.COM (Andrew Klossner)
Newsgroups: comp.sys.m88k
Subject: Re: Exception handling in the 88's
Message-ID: <10564@orca.wv.tek.com>
Date: 9 Apr 91 19:13:09 GMT
References: <28961@dime.cs.umass.edu>
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Reply-To: andrew@frip.wv.tek.com
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Organization: Tektronix, Wilsonville, Oregon
Lines: 17

[]

	"Method 1: Disable interrupts etc and don't save any context to
	memory.  Use the rte instruction to restore control registers.
	Shadowing remains disabled and a non-trap exception will crash
	the machine."

You still have to clean up any filth in the pipeline.  For example, on
a demand-paged system, it's possible that a page fault coincided with
the interrupt.  If the data exception bit is on in DMT0 (or is it DMT2?
.. they keep renumbering them), your interrupt handler is responsible
for handling the page fault -- you can't just return from interrupt.

I haven't seen a Unix system use "method 1," largely for this reason.

  -=- Andrew Klossner   (uunet!tektronix!frip.WV.TEK!andrew)    [UUCP]
                        (andrew%frip.wv.tek.com@relay.cs.net)   [ARPA]