On Jun 10, 2013, at 17:18 , Nathan Hjelm <hje...@lanl.gov> wrote: > On Sat, Jun 08, 2013 at 12:28:02PM +0200, George Bosilca wrote: >> All Windows objects that are managed as HANDLES can easily be modified to >> have static initializer. A clean solution is attached to the question at >> stackoverflow: >> http://stackoverflow.com/questions/3555859/is-it-possible-to-do-static-initialization-of-mutexes-in-windows > > Not the cleanest solution (and I don't know how handles work) so I held off > on proposing adding a static initializer until the windows code was gone.
Nothing really fancy, a HANDLE is basically an untyped location storage (a void*). >> That being said I think having a static initializer for a synchronization >> object is a dangerous thing. It has many subtleties and too many hidden >> limitations. As an example they can only be used on the declaration of the >> object, and can't be safely used for locally static object (they must be >> global). > > I have never seen any indication that a statically initialized mutex is not > safe for static objecs. The man page for thread_mutex_init uses the static > initializer on a static mutex: http://linux.die.net/man/3/pthread_mutex_init It is thread safe for global static objects, but might not be thread safe for local static objects. >> What are the instances in the Open MPI code where such a statically defined >> mutex need to be used before it has a chance of being correctly initialized? > > MPI_T_thread_init may be called from any thread (or multiple threads at the > same time). The current code uses atomics to protect the initialization of > the mutex. I would prefer to declare the mpit lock like: > > opal_mutex_t mpit_big_lock = OPAL_MUTEX_STATIC_INIT; > > and remove the atomics. It would be much cleaner and should work fine on all > currently supported platforms. OK, almost a corner-case. > how does mutex static initializer works A more detailed explanation in the "Static Initializers for Mutexes and Condition Variables" part of the http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_init.html George. > > -Nathan > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel
