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

   1 #include "pthread_impl.h"
   2
   3 static int pthread_mutex_timedlock_pi(pthread_mutex_t *restrict m, const struct timespec *restrict at)
   4 {
   5         int type = m->_m_type;
   6         int priv = (type & 128) ^ 128;
   7         pthread_t self = __pthread_self();
   8         int e;
   9
  10         if (!priv) self->robust_list.pending = &m->_m_next;
  11
  12         do e = -__syscall(SYS_futex, &m->_m_lock, FUTEX_LOCK_PI|priv, 0, at);
  13         while (e==EINTR);
  14         if (e) self->robust_list.pending = 0;
  15
  16         switch (e) {
  17         case 0:
  18                 /* Catch spurious success for non-robust mutexes. */
  19                 if (!(type&4) && ((m->_m_lock & 0x40000000) || m->_m_waiters)) {
  20                         a_store(&m->_m_waiters, -1);
  21                         __syscall(SYS_futex, &m->_m_lock, FUTEX_UNLOCK_PI|priv);
  22                         self->robust_list.pending = 0;
  23                         break;
  24                 }
  25                 /* Signal to trylock that we already have the lock. */
  26                 m->_m_count = -1;
  27                 return __pthread_mutex_trylock(m);
  28         case ETIMEDOUT:
  29                 return e;
  30         case EDEADLK:
  31                 if ((type&3) == PTHREAD_MUTEX_ERRORCHECK) return e;
  32         }
  33         do e = __timedwait(&(int){0}, 0, CLOCK_REALTIME, at, 1);
  34         while (e != ETIMEDOUT);
  35         return e;
  36 }
  37
  38 int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec *restrict at)
  39 {
  40         if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL
  41             && !a_cas(&m->_m_lock, 0, EBUSY))
  42                 return 0;
  43
  44         int type = m->_m_type;
  45         int r, t, priv = (type & 128) ^ 128;
  46
  47         r = __pthread_mutex_trylock(m);
  48         if (r != EBUSY) return r;
  49
  50         if (type&8) return pthread_mutex_timedlock_pi(m, at);
  51
  52         int spins = 100;
  53         while (spins-- && m->_m_lock && !m->_m_waiters) a_spin();
  54
  55         while ((r=__pthread_mutex_trylock(m)) == EBUSY) {
  56                 r = m->_m_lock;
  57                 int own = r & 0x3fffffff;
  58                 if (!own && (!r || (type&4)))
  59                         continue;
  60                 if ((type&3) == PTHREAD_MUTEX_ERRORCHECK
  61                     && own == __pthread_self()->tid)
  62                         return EDEADLK;
  63
  64                 a_inc(&m->_m_waiters);
  65                 t = r | 0x80000000;
  66                 a_cas(&m->_m_lock, r, t);
  67                 r = __timedwait(&m->_m_lock, t, CLOCK_REALTIME, at, priv);
  68                 a_dec(&m->_m_waiters);
  69                 if (r && r != EINTR) break;
  70         }
  71         return r;
  72 }
  73
  74 weak_alias(__pthread_mutex_timedlock, pthread_mutex_timedlock);