Inadequate Atomic Guarantees In QTHREAD_FASTLOCK_LOCK

[insertinterestingnamehere]

QTHREAD_FASTLOCK_LOCK and the related functions need to be rewritten to use atomic reads and writes instead of relying on the atomicity guarantees from x86. For example, there's currently a race condition between

qthreads/src/feb.c

Line 986 in d6ce514

QTHREAD_FASTLOCK_LOCK(&(m->lock));

and

qthreads/src/qthread.c

Line 652 in d6ce514

QTHREAD_FASTLOCK_UNLOCK(&(m->lock));

.

Note: this shows up readily in the hello_world_multi test.

[insertinterestingnamehere]

This also shows up inside the hash map when running the syncvar_prodcons test with thread sanitizer on. Specifically:

qthreads/src/hashmap.c

Line 412 in d6ce514

QTHREAD_FASTLOCK_LOCK(h->lock);

and

qthreads/src/hashmap.c

Line 219 in d6ce514

QTHREAD_FASTLOCK_UNLOCK(h->lock);