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.head = &self->robust_list.head;
  13                 self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
  14         }
  15
  16         old = m->_m_lock;
  17         own = old & 0x7fffffff;
  18         if (own == tid && (type&3) == PTHREAD_MUTEX_RECURSIVE) {
  19                 if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
  20                 m->_m_count++;
  21                 return 0;
  22         }
  23         if (own == 0x40000000) return ENOTRECOVERABLE;
  24
  25         if (m->_m_type & 128) {
  26                 if (m->_m_waiters) tid |= 0x80000000;
  27                 self->robust_list.pending = &m->_m_next;
  28         }
  29
  30         if ((own && (!(own & 0x40000000) || !(type & 4)))
  31             || a_cas(&m->_m_lock, old, tid) != old) {
  32                 self->robust_list.pending = 0;
  33                 return EBUSY;
  34         }
  35
  36         volatile void *next = self->robust_list.head;
  37         m->_m_next = next;
  38         m->_m_prev = &self->robust_list.head;
  39         if (next != &self->robust_list.head) *(volatile void *volatile *)
  40                 ((char *)next - sizeof(void *)) = &m->_m_next;
  41         self->robust_list.head = &m->_m_next;
  42         self->robust_list.pending = 0;
  43
  44         if (own) {
  45                 m->_m_count = 0;
  46                 m->_m_type |= 8;
  47                 return EOWNERDEAD;
  48         }
  49
  50         return 0;
  51 }
  52
  53 int pthread_mutex_trylock(pthread_mutex_t *m)
  54 {
  55         if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
  56                 return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
  57         return __pthread_mutex_trylock_owner(m);
  58 }