Interrupt storm with shared interrupt on digi(4)

[Peter Jeremy]

On 2008-Jun-03 10:21:35 -0400, John Baldwin <jhb at freebsd.org> wrote:
>> In the past, I have managed to avoid the problem by putting the Digi
>> card on a dedicated interrupt.  For reasons I don't understand, this
>> appears to mask the problem.
>
>That is because we leave interrupts masked until it gets an interrupt handler.
>Since digi(4) doesn't register a handler, we leave the interrupt masked 
>unless some other device is sharing the same interrupt and registers a 
>handler.

This is what I assumed but doesn't explain how having two digi boards
that share an interrupt with each other but nothing else winds up with
an interrupt storm.  I will have to investigate further...

>No.  Even better would be if there was a way to disable interrupt generation 
>in the digi(4) driver via some register.

Agreed.  Unfortunately, the only documentation is the Linux driver and it
doesn't appear to initialise the digi board any differently to FreeBSD.

>> Alternatively, can anyone suggest how I can disable or mask a specified
>> PCI interrupt?
>
>The problem is that in this case you have another driver that is using that 
>interrupt, so if you completely mask the interrupt the other driver will stop 
>getting interrupts and likely stop working.

I agree that this approach is a hack - but it will let me work around the
problem on the problematic system.

BTW, your MUA's list-reply configuration don't recognize that
freebsd-stable@ and stable@ are aliases.

-- 
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20080603/fca35a0c/attachment.pgp