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next step making barrier self-sync'd destruction safe

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i think this works, but it can be simplified. (next step)
This commit is contained in:
Rich Felker 2011-09-28 18:00:02 -04:00
parent 8f4a115e7d
commit 95b1479672
2 changed files with 18 additions and 6 deletions
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8
src/thread/pthread_barrier_destroy.c
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@ -5,8 +5,12 @@ void __vm_lock(int), __vm_unlock(void);
int pthread_barrier_destroy(pthread_barrier_t *b)
{
if (b->_b_limit < 0) {
int seq = b->_b_seq;
if (seq & 1) __wait(&b->_b_seq, 0, seq, 0);
if (b->_b_lock) {
int v;
a_or(&b->_b_lock, INT_MIN);
while ((v = b->_b_lock) & INT_MAX)
__wait(&b->_b_lock, 0, v, 0);
}
__vm_lock(-1);
__vm_unlock();
}

16
src/thread/pthread_barrier_wait.c
View File

@ -23,11 +23,12 @@ static int pshared_barrier_wait(pthread_barrier_t *b)
int limit = (b->_b_limit & INT_MAX) + 1;
int seq;
int ret = 0;
int v, w;
if (limit==1) return PTHREAD_BARRIER_SERIAL_THREAD;
while (a_swap(&b->_b_lock, 1))
__wait(&b->_b_lock, &b->_b_waiters, 1, 0);
while ((v=a_cas(&b->_b_lock, 0, limit)))
__wait(&b->_b_lock, &b->_b_waiters, v, 0);
seq = b->_b_seq;
@ -46,12 +47,19 @@ static int pshared_barrier_wait(pthread_barrier_t *b)
if (a_fetch_add(&b->_b_count, -1)==1) {
b->_b_seq++;
__wake(&b->_b_seq, -1, 0);
a_store(&b->_b_lock, 0);
if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
} else {
__wait(&b->_b_seq, 0, seq+1, 0);
}
/* Perform a recursive unlock suitable for self-sync'd destruction */
do {
v = b->_b_lock;
w = b->_b_waiters;
} while (a_cas(&b->_b_lock, v, v-1 & INT_MAX) != v);
if (v==INT_MIN+1 || (v==1 && w))
__wake(&b->_b_lock, 1, 0);
__vm_unlock();
return ret;