nsz Git - musl/blob - src/thread/pthread_cond_broadcast.c

   1 #include "pthread_impl.h"
   2
   3 static void unlock(pthread_cond_t *c)
   4 {
   5         a_dec(&c->_c_bcast);
   6         if (c->_c_leavers) __wake(&c->_c_bcast, -1, 0);
   7 }
   8
   9 int pthread_cond_broadcast(pthread_cond_t *c)
  10 {
  11         pthread_mutex_t *m;
  12         int w;
  13
  14         if (!c->_c_waiters) return 0;
  15         a_inc(&c->_c_bcast);
  16         if (!c->_c_waiters) {
  17                 unlock(c);
  18                 return 0;
  19         }
  20
  21         a_store(&c->_c_block, 0);
  22
  23         m = c->_c_mutex;
  24
  25         /* If mutex ptr is not available, simply wake all waiters. */
  26         if (m == (void *)-1) {
  27                 unlock(c);
  28                 __wake(&c->_c_block, -1, 0);
  29                 return 0;
  30         }
  31
  32         /* Move waiter count to the mutex */
  33         for (;;) {
  34                 w = c->_c_waiters;
  35                 a_fetch_add(&m->_m_waiters, w);
  36                 if (a_cas(&c->_c_waiters, w, 0) == w) break;
  37                 a_fetch_add(&m->_m_waiters, -w);
  38         }
  39
  40         /* Perform the futex requeue, waking one waiter unless we know
  41          * that the calling thread holds the mutex. */
  42         __syscall(SYS_futex, &c->_c_block, FUTEX_REQUEUE,
  43                 !m->_m_type || (m->_m_lock&INT_MAX)!=pthread_self()->tid,
  44                 INT_MAX, &m->_m_lock);
  45
  46         unlock(c);
  47         return 0;
  48 }