Re: Hang: sky2/DMAR (was [PATCH] sky2: Fix WARNING: atlib/dma-debug.c:902 check_sync)

From: Jarek Poplawski
Date: Fri Jan 22 2010 - 16:53:24 EST

On Fri, Jan 22, 2010 at 01:01:15PM -0500, Michael Breuer wrote:
> Kernel (git) with the following patches applied:
> af_packet.c (tpacket_snd version 3)
> sky2.c pskb_may_pull
> sky2 fix WARNING at lib/dma-debug.c check_sync

I guess, you meant the "sky2.c receive_copy" patch which you tested
earlier, or at least you managed to crash DMAR with that patch
before crashing it with Stephen's "lib/dma-debug.c check_sync" patch,

> Running with CONFIG_DMAR=n, system is stable.
> Running with the exact same source but CONFIG_DMAR=y I get the
> WARNING (see below) after about 36 hours of uptime (has varied from
> about 24 to about 48):
> Smolt profile:
> I'm also attaching dmesg.old (dmesg from the crash).
> Subsequent to this the system watchdog reboots the system (it's hung).
> Of interest: each and every time this has happened the system was
> under heavy RX load (win7 backup to a cifs share hosted on this
> server). Also, there is always a dhcp exchange of some sort
> preceding the event.
> It is possible that the event is re creatable without DMAR enabled,
> but I have been unsuccessful in doing so.

It would be nice to check now if it's re-creatable without the dhcp
exchange yet, or at least dhcp through the switch and the router,
because I suspect there might be something more than a simple drop
on the switch that affects sky2 stability.

Jarek P.
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