Subj : Re: Can C++ local static objects be made thread safe?
To   : comp.programming.threads
From : gottlobfrege
Date : Thu Feb 17 2005 12:05 pm


Marcin 'Qrczak' Kowalczyk wrote:
> gniccolai@yahoo.com (Giancarlo Niccolai) writes:
>
> > That's not following the pthread_once semantic: all the threads get
> > there even if once stuff is still NOT done.
>
> This is not true at least on Linux/NPTL: other threads calling
> pthread_once do wait for the first thread to finish.
>
> The documentation is not clear enough to judge.
>

Although I wouldn't call the docs 'clear' either, I think we can deduce
that the other threads must wait:

from
http://www.opengroup.org/onlinepubs/007908799/xsh/pthread_once.html
(first google result for pthread_once):

"On return from pthread_once(), it is guaranteed that init_routine()
has completed."

(And of course it says init_routine() is only called once.)  Thus
secondary threads must wait for the first thread to finish.

Tony

.