How can barriers be destroyable as soon as pthread_barrier_wait returns?

Question

This question is based on:

When is it safe to destroy a pthread barrier?

and the recent glibc bug report:

http://sourceware.org/bugzilla/show_bug.cgi

Answer 1

As far as I can see there is no need for pthread_barrier_destroy to be an immediate operation. You could have it wait until all threads that are still in their wakeup phase are woken up.

E.g you could have an atomic counter awakening that initially set to the number of threads that are woken up. Then it would be decremented as last action before pthread_barrier_wait returns. pthread_barrier_destroy then just could be spinning until that counter falls to 0.