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Q serial.c

Q serial.c

Post by kees » Sat, 23 Jun 2001 16:00:10



Hi
What may happen on a SMP machine if a serial port has been closed and the
closing stage is at shutdown() in serial.c in the call to free_IRQ  and
BEFORE the IRQ is really shutdown, a new character arrives which causes an
IRQ? Is it possible that the OTHER cpu  takes this interrupt and causes a
crash?

Kees

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Q serial.c

Post by Stuart MacDonal » Sat, 23 Jun 2001 23:00:11



Quote:> What may happen on a SMP machine if a serial port has been closed and the
> closing stage is at shutdown() in serial.c in the call to free_IRQ  and
> BEFORE the IRQ is really shutdown, a new character arrives which causes an
> IRQ? Is it possible that the OTHER cpu  takes this interrupt and causes a
> crash?

I'm looking at serial-5.05/serial.c. You'll notice at the
beginning of shutdown the saveflags(); cli(); calls.
This disables interrupts. The uart will not be able to
generate IRQs even if new characters arrive.

..Stu

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Q serial.c

Post by Jonathan Lundel » Sun, 24 Jun 2001 00:30:07




>>  What may happen on a SMP machine if a serial port has been closed and the
>>  closing stage is at shutdown() in serial.c in the call to free_IRQ  and
>>  BEFORE the IRQ is really shutdown, a new character arrives which causes an
>>  IRQ? Is it possible that the OTHER cpu  takes this interrupt and causes a
>>  crash?

>I'm looking at serial-5.05/serial.c. You'll notice at the
>beginning of shutdown the saveflags(); cli(); calls.
>This disables interrupts. The uart will not be able to
>generate IRQs even if new characters arrive.

The other CPU servicing the interrupt, was the question. cli()
doesn't affect that. This could presumably happen if shutdown() gets
run on a non-interrupt-servicing CPU, or if interrupts are
dynamically routed (eg round-robin).

Where can I find the 5.05 driver?
--
/Jonathan Lundell.
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Q serial.c

Post by Stuart MacDonal » Sun, 24 Jun 2001 00:40:05



Quote:> The other CPU servicing the interrupt, was the question. cli()
> doesn't affect that. This could presumably happen if shutdown() gets
> run on a non-interrupt-servicing CPU, or if interrupts are
> dynamically routed (eg round-robin).

Ah. Missed that.

Hm. Does appear to be a problem. Ted?

Quote:> Where can I find the 5.05 driver?

http://serial.sourceforge.net  I'm not sure which version is currently
in 2.4.latest, but it should be nearly 5.05.

..Stu

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1. serial console - lilo serial= no serial port input

I'm setting up a serial console on a machine for which the monitor
will go into the repair shop.  I've successfully set up getty to
take logins from the serial port, and I've successfully configured
the kernel to send boot messages to the serial port.  The final step
is setting up lilo.  Lilo works in that the boot prompt appears on
both the system console and on the serial port. However, I cannot
enter commands to the boot prompt from the serialport.  Following
manpage procedure, I transmit a break over the serial line in an
attempt to get lilo's attention.  It doesn't work.  Lilo listens only
to the system keyboard.  What's up?

System details: lilo-0.20-2 rpm from red hat 5.2, kernel 2.2.5,
otherwise a stock rh 5.2 i386 machine. Serial port connection: I'm running
kermit on a laptop.  I send breaks from kermit  as ctrl-\ b as indicated
in kermit man page. Kermit is ckermit-192.

I suppose that the simplest explanation is that I won't be able to get
lilo's attention unless I unplug the keyboard from the
to-be-monitorless system.  Possible?

Thanks,

Dick

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