[RFC] Use mutexes by default in db_open()

[Ralph Böhme]

On Wed, May 31, 2017 at 04:12:18PM +1000, Amitay Isaacs wrote:
> On Wed, May 31, 2017 at 3:29 PM, Ralph Böhme <slow at samba.org> wrote:
> 
> > Hi Amitay
> >
> > On Mon, May 29, 2017 at 12:21:50PM +1000, Amitay Isaacs wrote:
> > > Here's the summary of what I would like to propose:
> > >  1. CTDB ignores tdb_flags specified in DB_ATTACH controls, tdb flags are
> > > calculated based on the database model (or specific DB_ATTACH control)
> > >  2. For volatile databases, mutexes will be enabled by default
> > > (TDBMutexEnabled=1) when samba enables mutexes by default
> > > (dbwrap_tdb_mutexes:*=true)
> >
> > sorry, but I fail to understand how 1 and 2 could work together. If,
> > according
> > to 1, ctdb ignores the tdb_flags in the DB_ATTACH control, how is
> > disabling of
> > mutexes handled in step 2 when dbwrap_tdb_mutexes:*=false is set in
> > smb.conf
> > (while TDBMutexEnabled=1 still set for ctdb) ?
> >
> > *scratches head*
> >
>
> Obviously you have not ready my fully. Here's the statement you missed from
> previous email.
> 
> -------
> As a result, in clustered samba case, dbwrap_tdb_mutexes settings will be
> ignored for clustered (volatile) databases.
> ------

huh, sorry but for me this still doesn't combine with clause 2. Let me try to
rephrase it:

2. Whether mutexes are enabled or disabled for volatile databases is determined by
2.1. smb.conf dbwrap_tdb_mutexes setting on a standalone Samba server, or
2.2. ctdb tunable TDBMutexEnabled in a ctdb cluster

With 4.7 we change both defaults to yes and 1 respectively.

Got it? :)

-slow