Using source3 RPC servers as daemons causes deadlock with winbindd!

[Andreas Schneider]

On Friday 02 May 2014 16:56:03 Andrew Bartlett wrote:
> On Wed, 2014-04-30 at 17:37 +0200, Andreas Schneider wrote:
> > On Wednesday 30 April 2014 11:55:40 Andrew Bartlett wrote:
> > > The attached patches finally make the source3 winbindd code connect to
> > > the LSA and SAMR servers over ncalrpc rather than directly linking the
> > > shared library.
> > > 
> > > The problem is, in make test s3dc is set to use:
> > >         rpc_server:epmapper = external
> > >         rpc_server:spoolss = external
> > >         rpc_server:lsarpc = external
> > >         rpc_server:samr = external
> > >         rpc_server:netlogon = external
> > >         rpc_server:register_embedded_np = yes
> > >         
> > >         rpc_daemon:epmd = fork
> > >         rpc_daemon:spoolssd = fork
> > >         rpc_daemon:lsasd = fork
> > > 
> > > The issue is, when we connect to the RPC server, we lock up due to a
> > > recursive call to winbindd (otherwise prevented because of the
> > > winbind_off() call).
> > > 
> > > It can be reproduced with:
> > > make test TESTS=samba3.blackbox.smbclient_auth.plain
> > > 
> > > GDB backtraces for smbd and winbindd are attached.
> > > 
> > > It appears to be locking up looking via LSA lookupnames and an NSS call
> > > for unix group\nogroup
> > > 
> > > Do you think it is reasonable to expect the source3 LSA and SAMR servers
> > > to be able to service winbindd when not loaded as a shared library, or
> > > should we instead put an exception in for this (only use the pipes when
> > > in AD DC mode).
> > > 
> > > Your thoughts and comments would be most valued.  As mentioned above,
> > > the patch used the to reproduce this is also attached.
> > 
> > I'll leave today and will back on monday. Then I can look into this.
> > 
> > Maybe Simo has time ...
> 
> This patch causes other issues (probably because it defines up an extra
> domain), but appears to avoid the deadlock.  It might provide some
> inspiration for a correct fix here.

I haven't forgotten about it. But Günther and I have a talk next week at 
SambaXP and we try to get a prototype working till then. I will look into it 
as soon as we have something. It is still on my TODO list!



	-- andreas

-- 
Andreas Schneider                   GPG-ID: CC014E3D
Samba Team                             asn at samba.org
www.samba.org