112 lines
2.9 KiB
C
112 lines
2.9 KiB
C
#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
|
|
{
|
|
volatile int count;
|
|
volatile int last;
|
|
volatile int waiters;
|
|
volatile int finished;
|
|
};
|
|
|
|
int pthread_barrier_wait(pthread_barrier_t *b)
|
|
{
|
|
int limit = b->_b_limit;
|
|
struct instance *inst;
|
|
|
|
/* 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, 1);
|
|
inst = b->_b_inst;
|
|
|
|
/* First thread to enter the barrier becomes the "instance owner" */
|
|
if (!inst) {
|
|
struct instance new_inst = { 0 };
|
|
int spins = 200;
|
|
b->_b_inst = inst = &new_inst;
|
|
a_store(&b->_b_lock, 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|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) {
|
|
b->_b_inst = 0;
|
|
a_store(&b->_b_lock, 0);
|
|
if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
|
|
a_store(&inst->last, 1);
|
|
if (inst->waiters)
|
|
__wake(&inst->last, -1, 1);
|
|
} else {
|
|
a_store(&b->_b_lock, 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, 1);
|
|
|
|
return 0;
|
|
}
|