Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-12

[Ingo Molnar]

* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> Second, my ethernet doesn't work, and it really seems to be some kind
> of interrupt trouble.  It sends out ARPs but doesn't see them come
> back, and it also doesn't seem to know that it sent them out. I get
> the following:
> 
> NETDEV WATCHDOG: eth0: transmit timed out
> eth0: transmit timed out, tx_status 00 status e601.
>   diagnostics: net 0ccc media 8880 dma 0000003a fifo 0000
> eth0: Interrupt posted but not delivered -- IRQ blocked by another
> device?
>   Flags; bus-master 1, dirty 33(1) current 33(1)
>   Transmit list 00000000 vs. f75012a0.
>   0: @f7501200  length 80000043 status 8c010043
>   1: @f75012a0  length 8000007a status 0c01007a
>   2: @f7501340  length 8000002a status 0001002a
>   3: @f75013e0  length 80000098 status 0c010098
>   4: @f7501480  length 8000002a status 0001002a
>   5: @f7501520  length 8000002a status 0001002a
>   6: @f75015c0  length 8000002a status 0001002a
>   7: @f7501660  length 8000002a status 0001002a
>   8: @f7501700  length 80000043 status 0c010043
>   9: @f75017a0  length 80000043 status 0c010043
>   10: @f7501840  length 8000004f status 0c01004f
>   11: @f75018e0  length 8000004f status 0c01004f
>   12: @f7501980  length 80000043 status 0c010043
>   13: @f7501a20  length 8000007a status 0c01007a
>   14: @f7501ac0  length 80000098 status 0c010098
>   15: @f7501b60  length 8000002a status 8001002a 
> 
> I have a (from lspci) 
> 0000:02:08.0 Ethernet controller: 3Com Corporation 3c905C-TX/TX-M
> [Tornado] (rev 78)
> 
> 
> I can look into this further to see what the problem is. One funny
> note, on the vanilla kernel, my eth0 is at interrupt 177, but on the
> rt patched kernel its swapped with the sound card and is at interrupt
> 169. Well it's getting too late for me now (its 1am my time (01:00 for
> you European folks ;-) , and I need to get up at 6:30 am). Tomorrow,
> I'll hack on it some more.

yeah, please check this - you are the first one to report this issue.

A good first step would be to go switch to a non-PREEMPT_RT preemption
model (but to keep the -RT codebase) and see whether the breakage is
related to that. If the breakage goes away with say PREEMPT_DESKTOP then
i'd suggest to enable PREEMPT_HARDIRQS and PREEMPT_SOFTIRQS (but keep
PREEMPT_DESKTOP) - do these alone trigger the breakage? E.g. there was
an obscure timing bug in the floppy driver that only triggered with
PREEMPT_HARDIRQS enabled. So it's not out of question that there's some
other driver bug/race in hiding. The other possibility is some generic
-RT kernel breakage - like the SLAB issue was.

	Ingo
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