The previous barrier implementation did not fulfill the POSIX requirements
for when a barrier can be destroyed. Specifically, it was possible that
threads that haven't noticed yet that their round is complete still access
the barrier's memory, and that those accesses can happen after the barrier
has been legally destroyed.
The new algorithm does not have this issue, and it avoids using a lock
internally.
This patch replaces unsigned long int and 1UL with uint64_t and
(uint64_t) 1 to support ILP32 targets like x32.
[BZ #17870]
* nptl/sem_post.c (__new_sem_post): Replace unsigned long int
with uint64_t.
* nptl/sem_waitcommon.c (__sem_wait_cleanup): Replace 1UL with
(uint64_t) 1.
(__new_sem_wait_slow): Replace unsigned long int with uint64_t.
Replace 1UL with (uint64_t) 1.
* sysdeps/nptl/internaltypes.h (new_sem): Replace unsigned long
int with uint64_t.
This commit fixes semaphore destruction by either using 64b atomic
operations (where available), or by using two separate fields when only
32b atomic operations are available. In the latter case, we keep a
conservative estimate of whether there are any waiting threads in one
bit of the field that counts the number of available tokens, thus
allowing sem_post to atomically both add a token and determine whether
it needs to call futex_wake.
See:
https://sourceware.org/ml/libc-alpha/2014-12/msg00155.html
