github.com/afumu/libc@v0.0.6/musl/src/thread/pthread_mutex_unlock.c (about)

     1  #include "pthread_impl.h"
     2  
     3  int __pthread_mutex_unlock(pthread_mutex_t *m)
     4  {
     5  	pthread_t self;
     6  	int waiters = m->_m_waiters;
     7  	int cont;
     8  	int type = m->_m_type & 15;
     9  	int priv = (m->_m_type & 128) ^ 128;
    10  	int new = 0;
    11  	int old;
    12  
    13  	if (type != PTHREAD_MUTEX_NORMAL) {
    14  		self = __pthread_self();
    15  		old = m->_m_lock;
    16  		int own = old & 0x3fffffff;
    17  		if (own != self->tid)
    18  			return EPERM;
    19  		if ((type&3) == PTHREAD_MUTEX_RECURSIVE && m->_m_count)
    20  			return m->_m_count--, 0;
    21  		if ((type&4) && (old&0x40000000))
    22  			new = 0x7fffffff;
    23  		if (!priv) {
    24  			self->robust_list.pending = &m->_m_next;
    25  			__vm_lock();
    26  		}
    27  		volatile void *prev = m->_m_prev;
    28  		volatile void *next = m->_m_next;
    29  		*(volatile void *volatile *)prev = next;
    30  		if (next != &self->robust_list.head) *(volatile void *volatile *)
    31  			((char *)next - sizeof(void *)) = prev;
    32  	}
    33  	if (type&8) {
    34  		if (old<0 || a_cas(&m->_m_lock, old, new)!=old) {
    35  			if (new) a_store(&m->_m_waiters, -1);
    36  			__syscall(SYS_futex, &m->_m_lock, FUTEX_UNLOCK_PI|priv);
    37  		}
    38  		cont = 0;
    39  		waiters = 0;
    40  	} else {
    41  		cont = a_swap(&m->_m_lock, new);
    42  	}
    43  	if (type != PTHREAD_MUTEX_NORMAL && !priv) {
    44  		self->robust_list.pending = 0;
    45  		__vm_unlock();
    46  	}
    47  	if (waiters || cont<0)
    48  		__wake(&m->_m_lock, 1, priv);
    49  	return 0;
    50  }
    51  
    52  weak_alias(__pthread_mutex_unlock, pthread_mutex_unlock);