#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)
+{
+ int inc = vmlock[0]>0 ? -1 : 1;
+ if (a_fetch_add(vmlock, inc)==-inc && vmlock[1])
+ __wake(vmlock, -1, 1);
+}
+
+static int pshared_barrier_wait(pthread_barrier_t *b)
+{
+ int limit = (b->_b_limit & INT_MAX) + 1;
+ int ret = 0;
+ int v, w;
+
+ if (limit==1) return PTHREAD_BARRIER_SERIAL_THREAD;
+
+ while ((v=a_cas(&b->_b_lock, 0, limit)))
+ __wait(&b->_b_lock, &b->_b_waiters, v, 0);
+
+ /* 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;
+ 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);
+ while ((v=b->_b_count)>0)
+ __wait(&b->_b_count, &b->_b_waiters2, v, 0);
+ }
+
+ __vm_lock(+1);
+
+ /* 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 {
+ 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==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();
+
+ return ret;
+}
+
struct instance
{
int count;
/* Trivial case: count was set at 1 */
if (!limit) return PTHREAD_BARRIER_SERIAL_THREAD;
+ /* Process-shared barriers require a separate, inefficient wait */
+ if (limit < 0) return pshared_barrier_wait(b);
+
/* Otherwise we need a lock on the barrier object */
while (a_swap(&b->_b_lock, 1))
- __wait(&b->_b_lock, &b->_b_waiters, 1, 0);
+ __wait(&b->_b_lock, &b->_b_waiters, 1, 1);
inst = b->_b_inst;
/* First thread to enter the barrier becomes the "instance owner" */
int spins = 10000;
b->_b_inst = inst = &new_inst;
a_store(&b->_b_lock, 0);
- if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
+ if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
while (spins-- && !inst->finished)
a_spin();
a_inc(&inst->finished);
if (++inst->count == limit) {
b->_b_inst = 0;
a_store(&b->_b_lock, 0);
- if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
+ if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
a_store(&inst->last, 1);
if (inst->waiters)
- __wake(&inst->last, -1, 0);
+ __wake(&inst->last, -1, 1);
} else {
a_store(&b->_b_lock, 0);
- if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
- __wait(&inst->last, &inst->waiters, 0, 0);
+ if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
+ __wait(&inst->last, &inst->waiters, 0, 1);
}
/* Last thread to exit the barrier wakes the instance owner */
if (a_fetch_add(&inst->count,-1)==1 && a_fetch_add(&inst->finished,1))
- __wake(&inst->finished, 1, 0);
+ __wake(&inst->finished, 1, 1);
return 0;
}