[Samba] Samba daemons hang trying to lock locking.tdb

[Jeremy Allison]

On Tue, Jan 31, 2006 at 08:07:05PM +0100, Fermin Molina wrote:
> Hi,
> 
> After upgrade to samba 3.0.21b, the behaviour is the same.
> I think the problem must be related to TDB (Trivial DB) code. The call
> fcntl64() is trying to lock for write the file /var/cache/locking.tdb,
> but with the F_SETLKW file control command. This control command waits
> if the file is blocked. If another process locks for write this file,
> can we get a deadlock?

No, the fcntl locks are done to allow concurrent safe access
to the tdb's. The only way you can get a deadlock is if there
is a logic bug in the code, or if the underlying file system
is hanging on granting a lock.

/var/cache/locking.tdb is on a local filesystem on your
machine, correct ? Oftentimes locks don't work correctly
on remote mounted filesystems.

> The fact is that some hours after start samba, some smbd daemons hangs
> waiting to get a write lock to locking.tdb file. The windows clients
> associated with these smbd daemons get stalled and the user must to
> reset the machine (or I kill -9 these daemons).
> 
> Any clue?

We need more information on how to reproduce this, it's not
a generic logic bug I believe as it's not been widely reported.

Jeremy.