Date: Thu, 24 Sep 1998 19:56:47 -0400 (EDT) From: Simon Shapiro <shimon@simon-shapiro.org> To: Mike Smith <mike@smith.net.au> Cc: current@FreeBSD.ORG, bde@FreeBSD.ORG, "Justin T.Gibbs" <gibbs@plutotech.com> Subject: Re: options DPT_LOST_IRQ Message-ID: <XFMail.980924195647.shimon@simon-shapiro.org> In-Reply-To: <199809242030.NAA00623@dingo.cdrom.com>
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Mike Smith, On 24-Sep-98 you wrote:
> > >This option is necessary due to interrupts being eaten by the serial
> > >driver 'fast interrupt' code (which in some cases blocks interrupts
> > >longer than the DPT assert them).
> >
> > Wow. I thought that the fast interrupt code could only cause
> > interrupts
> > to be deferred, never eaten. Did anyone ever talk to Bruce about this?
> > I'd hate to have a situation where lots of drivers each have their own
> > little timeout handler to deal with this problem.
>
> Yes; the FAST_INTR() code basically looks like:
>
> fastintr: <- entry with PSL_I clear, interrupts masked
> call handler <- handler runs with interrupts masked
> sti <- reenable interrupts
> rti
>
> (I've left a lot out, obviously.)
>
> I actually thought as you did when I read Eivind's mail, but rereading
> the code this is actually the case.
>
> For all their efficiency benefits, I think fast interrupts are Evil.
I do not know about Evil, but I have a dislike for undeterministic
systems...
>
>
> --
> \\ Sometimes you're ahead, \\ Mike Smith
> \\ sometimes you're behind. \\ mike@smith.net.au
> \\ The race is long, and in the \\ msmith@freebsd.org
> \\ end it's only with yourself. \\ msmith@cdrom.com
>
>
>
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Sincerely Yours, Shimon@Simon-Shapiro.ORG
770.265.7340
Simon Shapiro
Unwritten code has no bugs and executes at twice the speed of mouth
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