[openib-general] Re: SDP: still getting sk_alloc() panic, any ideas?

[Libor Michalek]

On Mon, Jun 27, 2005 at 02:27:54PM -0700, Tom Duffy wrote:
> On Mon, 2005-06-27 at 11:17 -0700, Libor Michalek wrote:
> >   The problem is that each call to sk_alloc() is grabbing a reference to
> > the module, but it checks to make sure that there already is at least one
> > reference, if not the top BUG is triggered. In the case of the passive
> > connection there are no other references to the module. You can see that
> > the problem goes away if you open just one socket, even if you don't
> > listen on it, and then try the failing passive connect. When a socket is
> > created it actually grabs two references to the module, one at the sock
> > level and one at the sk level. The first reference at the sock level does
> > not trigger the BUG since it's through another code path. (try_module_get
> > vs. __module_get) This is why we only hit this during passive connect
> > to a system that has no active SDP sockets.
> > 
> >   Not sure the right way to fix this, maybe check to see if the socket
> > table size (dev_root_s.sk_entry) is greater then 0 in sdp_cm_req_handler()
> > before even performing the alloc...
> 
> Hrm.  That seems ugly.  How about a patch to upstream changing
> sk_alloc() to use try_module_get().

  I'm thinking the listen_lookup needs to be moved earlier in the
req_handler ahead of the sk_alloc, since it makes no sense to do
the alloc if we are not going to queue the new incomming connection,
since it just leads to a destroy in the same function.

-Libor