Date: Tue, 1 Dec 1998 14:30:14 +1100 From: Bruce Evans <bde@zeta.org.au> To: geoffb@demon.net, mike@smith.net.au Cc: andyf@speednet.com.au, bde@zeta.org.au, freebsd-current@FreeBSD.ORG, johan@granlund.nu, ortmann@sparc.isl.net Subject: Re: sio breakage Message-ID: <199812010330.OAA20453@godzilla.zeta.org.au>
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>> I was assuming the serial interface which is a fixed one breaking out of
>> the back of the Laptop had nothing to do with the PCMCIA,
>
>You're quite correct; it doesn't. There's *something* holding up both
>your interrupt handlers and the tty soft interrupt; maybe even possibly the
>same thing that causes the "calcru: negative time for ..." messages.
something()
{
asm("cli");
asm("sti");
}
This disables interrupts for 0 user instructions, but if a pagefault
occurs for reading the "sti" instruction, it disables interrupts for
hundreds, thousands or millions of kernel instructions.
something_more_likely()
{
asm("cli");
var = 0;
asm("sti");
}
This disables interrupts for 1 or 2 user instructions, but if a pagefault
occurs for reading a critical instruction or more likely for accessing
the variable, it disables interrupts for hundreds, thousands or millions
of kernel instructions.
Fixes:
kernel: send a fatal signal to applications that do this.
applications: don't do this. If interrupts must be disabled, then all
critical code and data must be within one page.
Bruce
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