#include "pthread_impl.h"
-static int vmlock[2];
-
-void __vm_lock(int inc)
-{
- for (;;) {
- int v = vmlock[0];
- if (inc*v < 0) __wait(vmlock, vmlock+1, v, 1);
- else if (a_cas(vmlock, v, v+inc)==v) break;
- }
-}
-
-void __vm_unlock(void)
-{
- if (vmlock[0]>0) a_dec(vmlock);
- else a_inc(vmlock);
- if (vmlock[1]) __wake(vmlock, 1, 1);
-}
+void __vm_lock_impl(int);
+void __vm_unlock_impl(void);
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;
while ((v=a_cas(&b->_b_lock, 0, limit)))
__wait(&b->_b_lock, &b->_b_waiters, v, 0);
- seq = b->_b_seq;
-
+ /* Wait for <limit> threads to get to the barrier */
if (++b->_b_count == limit) {
+ a_store(&b->_b_count, 0);
ret = PTHREAD_BARRIER_SERIAL_THREAD;
- b->_b_seq++;
- __wake(&b->_b_seq, -1, 0);
+ if (b->_b_waiters2) __wake(&b->_b_count, -1, 0);
} else {
a_store(&b->_b_lock, 0);
if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
- __wait(&b->_b_seq, 0, seq, 0);
+ while ((v=b->_b_count)>0)
+ __wait(&b->_b_count, &b->_b_waiters2, v, 0);
}
- __vm_lock(+1);
+ __vm_lock_impl(+1);
- if (a_fetch_add(&b->_b_count, -1)==1) {
- b->_b_seq++;
- __wake(&b->_b_seq, -1, 0);
+ /* Ensure all threads have a vm lock before proceeding */
+ if (a_fetch_add(&b->_b_count, -1)==1-limit) {
+ a_store(&b->_b_count, 0);
+ if (b->_b_waiters2) __wake(&b->_b_count, -1, 0);
} else {
- __wait(&b->_b_seq, 0, seq+1, 0);
+ while ((v=b->_b_count))
+ __wait(&b->_b_count, &b->_b_waiters2, v, 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);
+ } while (a_cas(&b->_b_lock, v, v==INT_MIN+1 ? 0 : v-1) != v);
+ /* Wake a thread waiting to reuse or destroy the barrier */
if (v==INT_MIN+1 || (v==1 && w))
__wake(&b->_b_lock, 1, 0);
- __vm_unlock();
+ __vm_unlock_impl();
return ret;
}