rsync + hammer + nfs = trouble

[Aggelos Economopoulos]

On Sunday 13 July 2008, Matthew Dillon wrote:
> 
> :Tried using hammer for the first time today. Created a hammer volume on
> :two partitions, exported it over nfs, mounted it on my fileserver and
> :tried rsyncing some GB of data. After 20+ GB, the machine starts acting
> :up: I can't start new processes (command line editing over ssh works though)
> :and the rsync processes on the non-dfly box is stuck. Taking a look at the
> :console, I can see three "cache_lock: blocked on 0x... (.filename.c.garbage)"
> :messages. Some nfs-hammer interaction perhaps?
> :
> :Aggelos
> 
>     It sounds like a buffer cache deadlock, which should be easy for me to
>     fix.  Were you reading from the NFS mount or writing to the NFS mount?

Only rsync (via nfs) was accessing the filesystem.

>     I'm assuming you are running the latest HEAD.  If so, please drop
>     into the debugger (e.g. ctl-alt-esc) and generate a crash dump, and
>     get it onto leaf so I can take a look.

I am running HEAD from ~28h ago. Unfortunately, IIRC the machine doesn't have
a dumpdev configured (yeah, I know). Is there any information I can get you
via DDB?

Aggelos