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 (type >= 4) {
  11                 if (!self->robust_list.off)
  12                         __syscall(SYS_set_robust_list,
  13                                 &self->robust_list, 3*sizeof(long));
  14                 self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
  15                 self->robust_list.pending = &m->_m_next;
  16         }
  17
  18         old = m->_m_lock;
  19         own = old & 0x7fffffff;
  20         if (own == tid && (type&3) == PTHREAD_MUTEX_RECURSIVE) {
  21                 if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
  22                 m->_m_count++;
  23                 return 0;
  24         }
  25
  26         if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, old, tid)!=old)
  27                 return EBUSY;
  28
  29         if (type < 4) return 0;
  30
  31         if (type >= 8) {
  32                 m->_m_lock = 0;
  33                 return ENOTRECOVERABLE;
  34         }
  35         m->_m_next = self->robust_list.head;
  36         m->_m_prev = &self->robust_list.head;
  37         if (self->robust_list.head)
  38                 self->robust_list.head[-1] = &m->_m_next;
  39         self->robust_list.head = &m->_m_next;
  40         self->robust_list.pending = 0;
  41         if (own) {
  42                 m->_m_count = 0;
  43                 m->_m_type += 8;
  44                 return EOWNERDEAD;
  45         }
  46
  47         return 0;
  48 }
  49
  50 int pthread_mutex_trylock(pthread_mutex_t *m)
  51 {
  52         if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
  53                 return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
  54         return __pthread_mutex_trylock_owner(m);
  55 }