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From: bing@galbp.LBP.HARRIS.COM (Bing Bang)
Newsgroups: comp.os.minix
Subject: Re: List of bugs and improvements I will post immediately
Message-ID: <1819@galbp.LBP.HARRIS.COM>
Date: Wed, 7-Oct-87 12:05:08 EDT
Article-I.D.: galbp.1819
Posted: Wed Oct  7 12:05:08 1987
Date-Received: Sat, 10-Oct-87 10:12:32 EDT
References: <1710@botter.cs.vu.nl>
Reply-To: bing@galbp.UUCP (Bing Bang)
Distribution: world
Organization: Harris/Lanier, Atlanta, GA
Lines: 42

In article <1710@botter.cs.vu.nl> ast@cs.vu.nl (Andy Tanenbaum) writes:
>On a different note, Andy Valencia just sent me a note saying that if you
>apply Bing Bang's recent fix to pipe.c, his RS-232 driver works, except that
>it still loses characters.  I think the problem is that phys_copy disables
>interrupts too long.  Will some brave souls please back up their disks,

err..... i hate to admit to this, but i have found several serious bugs in
the tty driver i posted since the posting... since doing that i am a bit
paranoid about posting again with out being absolutely sure things work.
i'll re-post the stuff quite soon.

about the interrupts, i have replaced the sequences of

pushf
cli
...
popf

to something like:

pushf
cli
movb al,0xe7
out 0x21,al		| mask off all but the com port interrupts
popf
...
xorb al,al
out 0x21,al		| mask off no interrupts

this is still not quite adaquate. because some of this sequences are in
programms that become re-entrant if the interrupts are on. it looks like we
have to keep track of what state the 8259 was and restore that state instead
of blindly turning on all the interrupts at the end of the sequence.

just simply getting rid of all the cli's has disasterous results. i tried it
and i think something with the keyboard interrupts goes bad, if i hit a key
at just the right time, the system goes haywire. after it stepped on my
hard disk supperblock, i decided not to persue that route.
-- 
Bing H. Bang           +----------------------------------------------------+
Harris/Lanier          |MSDOS and OS/2 (whenever it gets here): just say no.|
Atlanta GA             +----------------------------------------------------+