[Samba] "samba-tool backup offline" stuck

[Andrew Bartlett]

On Wed, 2019-11-13 at 09:23 +0100, Andrea Venturoli wrote:
> On 2019-11-11 09:41, Andrew Bartlett wrote:
> 
> > > > and what is the full backtrace on that tdbbackup?
> > > 
> > > You mean: compile with debug symbols, attach gdb and get stack trace?
> > > If so, I'll do it, but I'll need some time.
> > 
> > Yes, that's what I need.
> 
> Please, find it below:

> (gdb) bt
> #0  0x0000000800fcdab8 in _fcntl () from /lib/libc.so.7
> #1  0x0000000800c68908 in __thr_fcntl (fd=3, cmd=13)
>      at /usr/src/lib/libthr/thread/thr_syscalls.c:202
> #2  0x0000000800ed2127 in fcntl (fd=3, cmd=13) at 
> /usr/src/lib/libc/sys/fcntl.c:54
> #3  0x000000080082c83c in fcntl_lock (tdb=<optimized out>, rw=<optimized 
> out>, off=8,
>      len=<optimized out>, waitflag=<optimized out>) at 
> ../../common/lock.c:58
> #4  tdb_brlock (tdb=0x80161f000, rw_type=3, offset=8, len=1, 
> flags=<optimized out>)
>      at ../../common/lock.c:200
> #5  0x000000080082cd19 in tdb_nest_lock (tdb=0x80161f000, offset=8, 
> ltype=3,
>      flags=TDB_LOCK_WAIT) at ../../common/lock.c:390
> #6  0x0000000800831808 in _tdb_transaction_start (tdb=0x80161f000, 
> lockflags=TDB_LOCK_WAIT)
>      at ../../common/transaction.c:490
> #7  0x000000000040188b in backup_tdb (
>      old_name=0x7fffffffddd6 "/var/db/samba4/private/secrets.ldb",
>      new_name=0x80161c000 "/var/db/samba4/private/secrets.ldb.copy.tdb",
>      hash_size=<optimized out>, nolock=<optimized out>, 
> readonly=<optimized out>)
>      at ../../tools/tdbbackup.c:157
> #8  0x0000000000401528 in main (argc=<optimized out>, argv=0x7fffffffdb40)
>      at ../../tools/tdbbackup.c:360
> 
> 
> Don't know if this is enough, but I'll get more info if needed (just 
> tell me which info).

Thanks that shows what is normally the behaviour.

I was worried someone had patched fcntl for flock(), as some on Hurd
were trying to do (we told them not do, quite sternly).  

Regarding your problem, on linux I use lslocks to debug from here, you
can normally work out which process is holding the lock, which lock it
is waiting on (if any, marked with a *) and gdb that to work out what
is the matter with it, and perhaps why it is in that situation.

I'm not sure if that is available and within your skills set, but that
is how to progress this. 

Andrew Bartlett
-- 
Andrew Bartlett                       http://samba.org/~abartlet/
Authentication Developer, Samba Team  http://samba.org
Samba Developer, Catalyst IT          http://catalyst.net.nz/services/samba