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

   1 #include "pthread_impl.h"
   2
   3 int __pthread_mutex_trylock_owner(pthread_mutex_t *m)
   4 {
   5         int old, own;
   6         int type = m->_m_type & 15;
   7         pthread_t self = __pthread_self();
   8         int tid = self->tid;
   9
  10         if (!self->robust_list.off) {
  11                 __syscall(SYS_set_robust_list, &self->robust_list, 3*sizeof(long));
  12                 self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
  13         }
  14
  15         old = m->_m_lock;
  16         own = old & 0x7fffffff;
  17         if (own == tid && (type&3) == PTHREAD_MUTEX_RECURSIVE) {
  18                 if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
  19                 m->_m_count++;
  20                 return 0;
  21         }
  22         if (own == 0x40000000) return ENOTRECOVERABLE;
  23
  24         self->robust_list.pending = &m->_m_next;
  25
  26         if ((own && (!(own & 0x40000000) || !(type & 4)))
  27             || a_cas(&m->_m_lock, old, tid) != old) {
  28                 self->robust_list.pending = 0;
  29                 return EBUSY;
  30         }
  31
  32         m->_m_next = self->robust_list.head;
  33         m->_m_prev = &self->robust_list.head;
  34         if (self->robust_list.head)
  35                 self->robust_list.head[-1] = &m->_m_next;
  36         self->robust_list.head = &m->_m_next;
  37         self->robust_list.pending = 0;
  38
  39         if (own) {
  40                 m->_m_count = 0;
  41                 m->_m_type |= 8;
  42                 return EOWNERDEAD;
  43         }
  44
  45         return 0;
  46 }
  47
  48 int pthread_mutex_trylock(pthread_mutex_t *m)
  49 {
  50         if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
  51                 return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
  52         return __pthread_mutex_trylock_owner(m);
  53 }