src/thread/pthread_cond_timedwait.c

   1 #include "pthread_impl.h"
   2
   3 struct cm {
   4         pthread_cond_t *c;
   5         pthread_mutex_t *m;
   6 };
   7
   8 static void unwait(pthread_cond_t *c, pthread_mutex_t *m)
   9 {
  10         /* Removing a waiter is non-trivial if we could be using requeue
  11          * based broadcast signals, due to mutex access issues, etc. */
  12
  13         if (c->_c_mutex == (void *)-1) {
  14                 a_dec(&c->_c_waiters);
  15                 if (c->_c_destroy) __wake(&c->_c_waiters, 1, 0);
  16                 return;
  17         }
  18
  19         while (a_swap(&c->_c_lock, 1))
  20                 __wait(&c->_c_lock, &c->_c_lockwait, 1, 1);
  21
  22         if (c->_c_waiters2) c->_c_waiters2--;
  23         else a_dec(&m->_m_waiters);
  24
  25         a_store(&c->_c_lock, 0);
  26         if (c->_c_lockwait) __wake(&c->_c_lock, 1, 1);
  27
  28         a_dec(&c->_c_waiters);
  29         if (c->_c_destroy) __wake(&c->_c_waiters, 1, 1);
  30 }
  31
  32 static void cleanup(void *p)
  33 {
  34         struct cm *cm = p;
  35         unwait(cm->c, cm->m);
  36         pthread_mutex_lock(cm->m);
  37 }
  38
  39 int pthread_cond_timedwait(pthread_cond_t *restrict c, pthread_mutex_t *restrict m, const struct timespec *restrict ts)
  40 {
  41         struct cm cm = { .c=c, .m=m };
  42         int r, e=0, seq;
  43
  44         if (m->_m_type && (m->_m_lock&INT_MAX) != pthread_self()->tid)
  45                 return EPERM;
  46
  47         if (ts && ts->tv_nsec >= 1000000000UL)
  48                 return EINVAL;
  49
  50         pthread_testcancel();
  51
  52         a_inc(&c->_c_waiters);
  53
  54         if (c->_c_mutex != (void *)-1) {
  55                 c->_c_mutex = m;
  56                 while (a_swap(&c->_c_lock, 1))
  57                         __wait(&c->_c_lock, &c->_c_lockwait, 1, 1);
  58                 c->_c_waiters2++;
  59                 a_store(&c->_c_lock, 0);
  60                 if (c->_c_lockwait) __wake(&c->_c_lock, 1, 1);
  61         }
  62
  63         seq = c->_c_seq;
  64
  65         pthread_mutex_unlock(m);
  66
  67         do e = __timedwait(&c->_c_seq, seq, c->_c_clock, ts, cleanup, &cm, 0);
  68         while (c->_c_seq == seq && (!e || e==EINTR));
  69         if (e == EINTR) e = 0;
  70
  71         unwait(c, m);
  72
  73         if ((r=pthread_mutex_lock(m))) return r;
  74
  75         return e;
  76 }