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
  23         self->robust_list.pending = &m->_m_next;
  24
  25         if ((own && (!(own & 0x40000000) || !(type & 4)))
  26             || a_cas(&m->_m_lock, old, tid) != old) {
  27                 self->robust_list.pending = 0;
  28                 return EBUSY;
  29         }
  30
  31         m->_m_next = self->robust_list.head;
  32         m->_m_prev = &self->robust_list.head;
  33         if (self->robust_list.head)
  34                 self->robust_list.head[-1] = &m->_m_next;
  35         self->robust_list.head = &m->_m_next;
  36         self->robust_list.pending = 0;
  37
  38         if (type < 4) return 0;
  39
  40         if (type >= 8) {
  41                 m->_m_lock = 0;
  42                 return ENOTRECOVERABLE;
  43         }
  44
  45         if (own) {
  46                 m->_m_count = 0;
  47                 m->_m_type += 8;
  48                 return EOWNERDEAD;
  49         }
  50
  51         return 0;
  52 }
  53
  54 int pthread_mutex_trylock(pthread_mutex_t *m)
  55 {
  56         if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
  57                 return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
  58         return __pthread_mutex_trylock_owner(m);
  59 }