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

   1 #include "pthread_impl.h"
   2
   3 int pthread_mutex_trylock(pthread_mutex_t *m)
   4 {
   5         int tid;
   6         int own;
   7         pthread_t self;
   8
   9         if (m->_m_type == PTHREAD_MUTEX_NORMAL)
  10                 return a_swap(&m->_m_lock, EBUSY);
  11
  12         self = pthread_self();
  13         tid = self->tid | 0x80000000;
  14
  15         if (m->_m_type >= 4) {
  16                 if (!self->robust_list.off)
  17                         syscall(SYS_set_robust_list,
  18                                 &self->robust_list, 3*sizeof(long));
  19                 self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
  20                 self->robust_list.pending = &m->_m_next;
  21         }
  22
  23         if (m->_m_lock == tid && (m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE) {
  24                 if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
  25                 m->_m_count++;
  26                 return 0;
  27         }
  28
  29         own = m->_m_lock;
  30         if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, own, tid)!=own)
  31                 return EBUSY;
  32
  33         m->_m_count = 1;
  34
  35         if (m->_m_type < 4) return 0;
  36
  37         if (m->_m_type >= 8) {
  38                 m->_m_lock = 0;
  39                 return ENOTRECOVERABLE;
  40         }
  41         m->_m_next = self->robust_list.head;
  42         m->_m_prev = &self->robust_list.head;
  43         if (self->robust_list.head)
  44                 self->robust_list.head[-1] = &m->_m_next;
  45         self->robust_list.head = &m->_m_next;
  46         self->robust_list.pending = 0;
  47         if (own) {
  48                 m->_m_type += 8;
  49                 return EOWNERDEAD;
  50         }
  51
  52         return 0;
  53 }