[9fans] Weird error.

[9fans] Weird error.

[Dan Cross]

I ran into this error trying to open /dev/eia1.  Has anyone else seen
it?  I haven't investigated it further, but it shows up after the first
either the first read or write from/to the serial port after the
following sequence of events:

(1) boot
(2) open the serial port
(3) read and write from it
(4) close it
(5) reopen it

Any ideas?

	- Dan C.

Re: [9fans] Weird error.

[Russ Cox]

what is the error?

Re: [9fans] Weird error.

[Dan Cross]

> I ran into this error trying to open /dev/eia1.  Has anyone else seen
> it?  I haven't investigated it further, but it shows up after the first
> either the first read or write from/to the serial port after the
> following sequence of events:
> 
> (1) boot
> (2) open the serial port
> (3) read and write from it
> (4) close it
> (5) reopen it
> 
> Any ideas?

Whoops.  It would help if I included the error.

Sun Jan 19 12:45:36: mpintrenable: multiple botch irq3, tbdf 5000000, lo 00000979, n 00000979
Sun Jan 19 12:45:36: intrenable: couldn't enable irq 3, tbdf 0xFFFFFFFF for COM2

That's from my clog's.  I stripped out some carriage returns, though.  Thanks!

	- Dan C.

Re: [9fans] Weird error.

[Richard Miller]

> Sun Jan 19 12:45:36: mpintrenable: multiple botch irq3, tbdf 5000000, lo 00000979, n 00000979

It's a benign error message resulting from the interaction of three
mostly harmless bugs:

1.  intdisable() on x86 MP architecture doesn't actually disable
interrupts.  The comment says:
	 * For now, none of this will work with the APIC code,

2.  i8250disable() marks the UART disabled after calling intdisable(),
without checking whether the disable succeeded.  So the next time the
UART device is opened the interrupt is enabled again.

3.  mpintrenablex() doesn't distinguish correctly between enabling a
device twice and enabling multiple devices (or multifunction devices)
which share an interrupt.

I think 2.  would be the easiest to fix, for example as follows:

/sys/src/9/pc/fns.h:61 c fns.h:61
< void	intrdisable(int, void (*)(Ureg *, void *), void*, int, char*);
---
> int	intrdisable(int, void (*)(Ureg *, void *), void*, int, char*);
/sys/src/9/pc/trap.c:67 c trap.c:67
< void
---
> int
/sys/src/9/pc/trap.c:79 c trap.c:79
< 		return;
---
> 		return -1;
/sys/src/9/pc/trap.c:95 a trap.c:96
> 	return 0;
/sys/src/9/pc/uarti8250.c:530,531 c uarti8250.c:530,531
< 		intrdisable(ctlr->irq, i8250interrupt, uart, ctlr->tbdf, uart->name);
< 		ctlr->iena = 0;
---
> 		if(intrdisable(ctlr->irq, i8250interrupt, uart, ctlr->tbdf, uart->name) == 0)
> 			ctlr->iena = 0;

Re: [9fans] Weird error.

[Dan Cross]

> It's a benign error message resulting from the interaction of three
> mostly harmless bugs:

Cool.  Thanks for the great explanation, Richard.

	- Dan C.