Re: [PATCH] NLM: hold BKL when clearing global lockd task and serv vars

[Jeff Layton <jlayton@redhat.com>]

On Mon, 7 Apr 2008 12:45:01 -0400
Christoph Hellwig <hch@infradead.org> wrote:

> On Mon, Apr 07, 2008 at 09:38:34AM -0400, Jeff Layton wrote:
> > The global task and serv pointers for lockd are normally protected by
> > the nlmsvc_mutex. The exception is when the lockd exits abnormally. When
> > this occurs, these variables are cleared without any locking.
> 
> Shouldn't we get rid of the case where it exits abnormally instead?
> 

Not a bad idea. After chatting with Christoph a bit on IRC, I suppose
we have 2 options if we want to pursue this. When we get an unexpected
error from svc_recv(), we could:

1) sleep for a bit and then retry

2) call schedule() and sleep until kthread_stop shuts down the thread

I think #1 is probably the best option. It's certainly the more fault
tolerant. That also fixes another potential problem -- right now if the
thread exits and the nlmsvc_users count isn't 0, then we can
potentially BUG() on the next lockd_up/lockd_down.

Any thoughts on what an appropriate sleep timeout should be when this
happens? I was thinking 1s or so...

Trond, Bruce, any thoughts?

-- 
Jeff Layton <jlayton@redhat.com>