On Mon, 12 Aug 2002 [EMAIL PROTECTED] wrote:
> On Mon, Aug 12, 2002 at 01:23:06PM +0100, Gavin Atkinson wrote:
> > ...
> > I have an i386 toshiba laptop, running FreeBSD 5.0-CURRENT #4: Sat Aug 10
> > 13:27:55 BST 2002. I can get a 100% reproducible hang by doing the
> > following:
> > - Connect a serial cable between my laptop and a PC
> > - run "tip -9600 com1"
> > (where com1 in /etc/remote is the default:
> > "com1:dv=/dev/cuaa0:br#9600:pa=none:")
> > - power down the PC.
> > My laptop hangs solid, and DDB cannot be entered from the keyboard. Note
> > that if I close tip before powering down the PC, i don't get a hang. I am
> > not using ACPI.
> > Interestingly, if I type something and then power up the PC again, that
> > character will echo on the screen before locking up again. By
> > power-cycling the PC frequently, i could actually carry on using my
> > laptop. Power cycling the PC (either on->off or off->on) seems to unlock
> > the laptop for a fraction of a second.
> > ...
> i have similar symptoms on my toshiba tecra 8000 under -stable ever since
> i installed fbsd on it (~4.1 i think), fbsd freezes when whatever terminal
> emulation (tip, cu , minicom) is still running when the remote side is
> powered down or the serial line is disconnected. but when the remote
> side (pc, router, ...) is powered on or the serial line is connected
> again fbsd unfreezes and continues to work. i had the "unlocks the
> laptop for a fraction of a second" just once when the remote side was
> an amiga 500...
> imho this is enirely related to (some) toshiba serial interfaces, at least
> i haven't seen this behaviour on other pcs running fbsd so far
It is most likely a hardware problem that causes endless sio interrupts,
most likely ones for modem status changes. sio doesn't handle this
gracefully. It may spin forever in the interrupt handler or keep
returning to the interrupt handler because changes or interrupts to
report changes (respectively) happen faster than they can be processed.
Some serial drivers have an option to not use the interrupt for modem
status changes and/or automatically don't use it when CLOCAL is set.
Try not using it in all cases by changing all instances of IER_EMSC
in sio.c to 0.
Look at the interrupt counts after doing something to bring the system
back to see if sio handled endless interrupts while the system was hung.
You would need to add an internal counter in the interrupt handler
(siointr1()) to detect internal looping.
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