[PATCH] malloc: Ensure that ptmalloc_init runs only once

[Florian Weimer]

* Siddhesh Poyarekar via Libc-alpha:

> It is possible that multiple threads simultaneously enter
> ptmalloc_init and succeed the < 0 check.  Make the comparison and
> setting of __malloc_initialized atomic so that only one of them goes
> through.  Additionally, if a thread sees that another thread is
> running the initialization (i.e. __malloc_initialized == 0) then wait
> till it is done.

No, this cannot happen because pthread_create calls malloc before
creating the new thread.

Thanks,
Florian