Re: [Xen-devel] Grant Table Network Issues

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 13 Aug 2005, at 19:59, Michael Vrable wrote:

> The line causing trouble is "BUG_ON(in_irq())".  In this example, I had
> tcpdump running in both domains; this seems to trigger the problem more
> reliably.  I've also seen a similar crash with a TCP connection, but it
> takes a few packets before this shows up (the handshake completes, and
> the crash happens about the time data packets come back from domain-0;
> if checksumming optimizations are enabled, it seems the packets are
> dropped so I don't see a crash but I don't get any data either).
On the stack trace, at irq_exit() you definitely have no hardirqs or 
softirqs in progress. But somehow, at kmap_skb_frag(), the hardirq 
section of the preempt mask has become non-zero. You can't have been 
preempted to another cpu during any of this because the preempt mask is 
continuously non-zero throughout original irq handling and subsequent 
softirq handling.
The only code between irq_exit and kmap_skb_frag on the stack trace is 
unmodified Linux code. Assuming that is all correct (and presumably the 
same whether we enable grant tables or not) I might guess another 
interrupt arrives and the handler corrupts things?
 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel