[PATCH] Remove all uses of talloc_autofree_context() from our code (except for test)

[Volker Lendecke]

On Wed, Jul 26, 2017 at 08:09:11AM -0400, Simo wrote:
> On Tue, 2017-07-25 at 13:04 -0700, Jeremy Allison via samba-technical
> wrote:
> > On Tue, Jul 25, 2017 at 09:58:06PM +0200, Volker Lendecke wrote:
> > > On Tue, Jul 25, 2017 at 12:37:24PM -0700, Jeremy Allison wrote:
> > > > > Does "smbcontrol smbd pool-usage" still work after this change?
> > > > 
> > > > No. If we're not using the global null_context within
> > > > talloc anymore, then pool usage doesn't have a central
> > > > place to track all allocations off it.
> > > 
> > > That's tough. I definitely want pool-usage to be available
> > > everywhere
> > > and always. When you need it, it's too late to activate it.
> > 
> > Having it available "everywhere and always" is inconsistent
> > with the design criteria behind this patchset. For that you
> > need a completely MT-safe talloc - you know it and I know it :-).
> 
> Jeremy,
> we can still have it by having a pool of counters instead.
> 
> In the main thread you have a linked list of structs reachable from the
> main thread. And only ever operated on with mutexes.
> 
> Each structs represents a thread and points to a thread bound variable
> that is ever only touched by the thread.
> This way you can use it from threads without locking.
> 
> The tricky part is reading it for reporting without locks, I leave that
> as an exercise for the reader (use memory barriers).

smbcontrol pool-usage prints the whole hierarchy. This is important if
you want to find out what kind of object you leak and if for example
is was accidentially hung off a long-term context. It's not a matter
of a simple counter. And walking the whole tree that belongs to
another thread is more than just using memory barriers (not knowing
how to do even that portably...).

Volker

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