1 #include "pthread_impl.h"
3 void __vm_lock_impl(int);
4 void __vm_unlock_impl(void);
6 static int pshared_barrier_wait(pthread_barrier_t *b)
8 int limit = (b->_b_limit & INT_MAX) + 1;
12 if (limit==1) return PTHREAD_BARRIER_SERIAL_THREAD;
14 while ((v=a_cas(&b->_b_lock, 0, limit)))
15 __wait(&b->_b_lock, &b->_b_waiters, v, 0);
17 /* Wait for <limit> threads to get to the barrier */
18 if (++b->_b_count == limit) {
19 a_store(&b->_b_count, 0);
20 ret = PTHREAD_BARRIER_SERIAL_THREAD;
21 if (b->_b_waiters2) __wake(&b->_b_count, -1, 0);
23 a_store(&b->_b_lock, 0);
24 if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
25 while ((v=b->_b_count)>0)
26 __wait(&b->_b_count, &b->_b_waiters2, v, 0);
31 /* Ensure all threads have a vm lock before proceeding */
32 if (a_fetch_add(&b->_b_count, -1)==1-limit) {
33 a_store(&b->_b_count, 0);
34 if (b->_b_waiters2) __wake(&b->_b_count, -1, 0);
36 while ((v=b->_b_count))
37 __wait(&b->_b_count, &b->_b_waiters2, v, 0);
40 /* Perform a recursive unlock suitable for self-sync'd destruction */
44 } while (a_cas(&b->_b_lock, v, v==INT_MIN+1 ? 0 : v-1) != v);
46 /* Wake a thread waiting to reuse or destroy the barrier */
47 if (v==INT_MIN+1 || (v==1 && w))
48 __wake(&b->_b_lock, 1, 0);
63 int pthread_barrier_wait(pthread_barrier_t *b)
65 int limit = b->_b_limit;
66 struct instance *inst;
68 /* Trivial case: count was set at 1 */
69 if (!limit) return PTHREAD_BARRIER_SERIAL_THREAD;
71 /* Process-shared barriers require a separate, inefficient wait */
72 if (limit < 0) return pshared_barrier_wait(b);
74 /* Otherwise we need a lock on the barrier object */
75 while (a_swap(&b->_b_lock, 1))
76 __wait(&b->_b_lock, &b->_b_waiters, 1, 1);
79 /* First thread to enter the barrier becomes the "instance owner" */
81 struct instance new_inst = { 0 };
83 b->_b_inst = inst = &new_inst;
84 a_store(&b->_b_lock, 0);
85 if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
86 while (spins-- && !inst->finished)
88 a_inc(&inst->finished);
89 while (inst->finished == 1)
90 __syscall(SYS_futex, &inst->finished, FUTEX_WAIT,1,0);
91 return PTHREAD_BARRIER_SERIAL_THREAD;
94 /* Last thread to enter the barrier wakes all non-instance-owners */
95 if (++inst->count == limit) {
97 a_store(&b->_b_lock, 0);
98 if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
99 a_store(&inst->last, 1);
101 __wake(&inst->last, -1, 1);
103 a_store(&b->_b_lock, 0);
104 if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
105 __wait(&inst->last, &inst->waiters, 0, 1);
108 /* Last thread to exit the barrier wakes the instance owner */
109 if (a_fetch_add(&inst->count,-1)==1 && a_fetch_add(&inst->finished,1))
110 __wake(&inst->finished, 1, 1);