Re: [Libmesh-devel] Major Problem With Singleton::Setup::Setup()!

[Roy S. <roy...@ic...>]

On Fri, 16 Aug 2013, Derek Gaston wrote:

> We're seeing hard locks on some machines in Singleton::Setup::Setup()!
> 
> The problem is that it's trying to create a scoped_lock using a mutex that is defined in that file.
> 
> Apparently that mutex is not guaranteed to have been initialized at the point where we're calling that function (or
> something) and it is just hanging while trying to acquire that lock!

Hmm... remote_elem_mtx should only get constructed at static
initialization time before main() gets called, and
RemoteElem::create() should only get called from
LibMeshInit::LibMeshInit() afterwards.

You're not creating a global LibMeshInit object, are you?

> I commented out that scoped_lock line and then the binary runs just fine.

Hmmm... would you replace that global mutex with two locals?  Maybe
there's some problem with a mutex constructor being called before we
init TBB?

> Why do we need to lock in those functions?  Surely the
> Singleton::Setup stuff is NOT going to get called in a loop.

You're right; the Setup constructor should be called at static init
time and the setup() call should be at LibMeshInit constructor time.

> How do we want to proceed?

It looks like we've got redundant locks that we can safely get rid
of... but I'd like to actually *understand* the problem too, and that
hasn't happened for me yet.
---
Roy