implement priority inheritance mutexes

[musl] / src / thread / pthread_mutex_trylock.c

diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c
index 50a815a..37e5c47 100644 (file)
--- a/src/thread/pthread_mutex_trylock.c
+++ b/src/thread/pthread_mutex_trylock.c
@@ -1,53 +1,74 @@
 #include "pthread_impl.h"
 
-int pthread_mutex_trylock(pthread_mutex_t *m)
+int __pthread_mutex_trylock_owner(pthread_mutex_t *m)
 {
-       int tid;
-       int own;
-       pthread_t self;
+       int old, own;
+       int type = m->_m_type;
+       pthread_t self = __pthread_self();
+       int tid = self->tid;
 
-       if (m->_m_type == PTHREAD_MUTEX_NORMAL)
-               return -a_swap(&m->_m_lock, 1) & EBUSY;
-
-       self = pthread_self();
-       tid = self->tid | 0x80000000;
-
-       if (m->_m_type >= 4) {
-               if (!self->robust_list.off)
-                       syscall(SYS_set_robust_list,
-                               &self->robust_list, 3*sizeof(long));
-               self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
-               self->robust_list.pending = &m->_m_next;
+       old = m->_m_lock;
+       own = old & 0x3fffffff;
+       if (own == tid) {
+               if ((type&8) && m->_m_count<0) {
+                       old &= 0x40000000;
+                       m->_m_count = 0;
+                       goto success;
+               }
+               if ((type&3) == PTHREAD_MUTEX_RECURSIVE) {
+                       if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
+                       m->_m_count++;
+                       return 0;
+               }
        }
+       if (own == 0x3fffffff) return ENOTRECOVERABLE;
+       if (own || (old && !(type & 4))) return EBUSY;
 
-       if (m->_m_lock == tid && (m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE) {
-               if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
-               m->_m_count++;
-               return 0;
+       if (type & 128) {
+               if (!self->robust_list.off) {
+                       self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
+                       __syscall(SYS_set_robust_list, &self->robust_list, 3*sizeof(long));
+               }
+               if (m->_m_waiters) tid |= 0x80000000;
+               self->robust_list.pending = &m->_m_next;
        }
+       tid |= old & 0x40000000;
 
-       own = m->_m_lock;
-       if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, own, tid)!=own)
+       if (a_cas(&m->_m_lock, old, tid) != old) {
+               self->robust_list.pending = 0;
+               if ((type&12)==12 & m->_m_waiters) return ENOTRECOVERABLE;
                return EBUSY;
+       }
 
-       m->_m_count = 1;
-
-       if (m->_m_type < 4) return 0;
-
-       if (m->_m_type >= 8) {
-               m->_m_lock = 0;
-               return ENOTRECOVERABLE;
+success:
+       if ((type&8) && m->_m_waiters) {
+               int priv = (type & 128) ^ 128;
+               __syscall(SYS_futex, &m->_m_lock, FUTEX_UNLOCK_PI|priv);
+               self->robust_list.pending = 0;
+               return (type&4) ? ENOTRECOVERABLE : EBUSY;
        }
-       m->_m_next = self->robust_list.head;
+
+       volatile void *next = self->robust_list.head;
+       m->_m_next = next;
        m->_m_prev = &self->robust_list.head;
-       if (self->robust_list.head)
-               self->robust_list.head[-1] = &m->_m_next;
+       if (next != &self->robust_list.head) *(volatile void *volatile *)
+               ((char *)next - sizeof(void *)) = &m->_m_next;
        self->robust_list.head = &m->_m_next;
        self->robust_list.pending = 0;
-       if (own) {
-               m->_m_type += 8;
+
+       if (old) {
+               m->_m_count = 0;
                return EOWNERDEAD;
        }
 
        return 0;
 }
+
+int __pthread_mutex_trylock(pthread_mutex_t *m)
+{
+       if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
+               return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
+       return __pthread_mutex_trylock_owner(m);
+}
+
+weak_alias(__pthread_mutex_trylock, pthread_mutex_trylock);