#include "pthread_impl.h"
+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();
+
+ /* 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;
- int last;
- int waiters;
- int finished;
+ volatile int count;
+ volatile int last;
+ volatile int waiters;
+ volatile int finished;
};
int pthread_barrier_wait(pthread_barrier_t *b)
/* 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" */
if (!inst) {
struct instance new_inst = { 0 };
- int spins = 10000;
+ int spins = 200;
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);
while (inst->finished == 1)
- __syscall(SYS_futex, &inst->finished, FUTEX_WAIT,1,0);
+ __syscall(SYS_futex,&inst->finished,FUTEX_WAIT|FUTEX_PRIVATE,1,0) != -ENOSYS
+ || __syscall(SYS_futex,&inst->finished,FUTEX_WAIT,1,0);
return PTHREAD_BARRIER_SERIAL_THREAD;
}
/* Last thread to enter the barrier wakes all non-instance-owners */
if (++inst->count == limit) {
-a_spin(); a_spin();
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;
}