Date: Wed, 02 Dec 1998 00:44:39 -0800 From: Mike Smith <mike@smith.net.au> To: Peter Jeremy <peter.jeremy@auss2.alcatel.com.au> Cc: current@FreeBSD.ORG Subject: Re: sio breakage Message-ID: <199812020844.AAA05482@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 02 Dec 1998 18:48:28 %2B1100." <98Dec2.184751est.40352@border.alcanet.com.au>
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> Bruce Evans <bde@zeta.org.au> wrote:
>
> >something_more_likely()
> >{
> > asm("cli");
> > var = 0;
> > asm("sti");
> >}
>
> >Fixes:
> >kernel: send a fatal signal to applications that do this.
>
> I'd suggest sending SIGBUS, with the interrupts enabled. This would
> allow the application to recover if necessary.
That's the normal practice; I suspect that the problem is that the i386
doesn't trap attempts to clear PSL_I if PSL_IOPL is set, so you can't
guarantee that this will be detected cleanly. (I may be wrong on this;
I'd have to check the code more carefully.)
> >applications: don't do this.
>
> I don't believe this is reasonable. We should provide some safe way
> for an application program to execute code with interrupts disabled.
> Amongst other applications, XFree86 needs this.
It shouldn't (ideally). If it does, this is clearly indicative of a
need to move some of the server code into the kernel, or in some other
architecturally clean fashion provide the currently missing assurances
pertaining to running with interrupts disabled.
--
\\ 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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