interrupt handlers in -current

[Duncan Barclay]

On 05-Jun-2003 M. Warner Losh wrote:
> In message: <XFMail.20030605220236.dmlb at dmlb.org>
>             Duncan Barclay <dmlb at dmlb.org> writes:
>: This is more of a confirmation of my understanding than anything else.
>: In -current, should an interrupt thread be created you set up an interrupt
>: handler? If so, then I'd better check my code because I haven't got one!
> 
> No.  Just because we handle interrupts in a thread doesn't mean client
> devices need to create a thread.  The thread is creted automatically
> and the routine passed to bus_setup_intr() is then called when an
> interrupt happens.

Rereading what I wrote, I might have mistyped and asked the wrong question.

I think what you saying is that bus_setup_intr() doesn't create the thread,
(in the sense of it appear in ps -ax?)
but a thread is created automatically when the first interrupt occurs?

> You can create threads, taskqueues and other things, but those aren't
> required.

Good - bus_dma is warping my head too much...I think I've got it right.

>: If a PCI device generates an interrupt and there is no handler does the
>: kernel report a stary interrupt?
> 
> You'll likely see an interrupt storm.  Since the PCI device generates
> a level interrupt, the ISRs are run and the level interrupt is still
> high, so another interrupt is generated, etc.  on 4.x this was fatal,
> but on 5.x the system can continue to run in a degraded manner.
> 
>: -current for me is 5.1-BETA1 and I'm doing a driver for the BCM 4401 NIC.
>: I'm transmitting packets but my handler isn't being called to clean up the
>: DMA.
> 
> So you are doing bus_setup_intr() and that routine is never called?

Yup.

> What does vmstat say?  I'd expect to see something like:
> 
> % vmstat -i
> uhci0 irq10                   26083          1
># cause the interrupt to happen
> % vmstat -i
> uhci0 irq10                   26026083     2683
># eg, a huge number all of a sudden

If I load the kld for the driver and it attaches, nothing appears
in vmstat -i, or ps -ax. Unfortunately, I've screwed up a lock in the ioctl
hander and witness is panic'ing when I ifconfig the interface. As it
is now bedtime I'll fix it tomorrow morning and report back.

> It may also be the case that the interrupt for this isn't being
> properly routed.  5.1-BETA has a bug that, for some laptop machines,
> interrupts aren't properly routed.  5.1-RELEASE has fixed this.

Okay, I'll do a reinstall. This probably won't happen until after the
weekend because I'm going away.

Anyway, I'm pleased with my progress as I can see arp requests hitting
the wire before it panics.

> Warner

Thanks,

Duncan

-- 
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Duncan Barclay  | 
dmlb at dmlb.org   | 
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