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