fix false ownership of mutexes due to tid reuse, using robust list

[musl] / src / thread / pthread_mutex_trylock.c

diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c
index 850fcb9..f871e9e 100644 (file)
--- a/src/thread/pthread_mutex_trylock.c
+++ b/src/thread/pthread_mutex_trylock.c
@@ -7,12 +7,9 @@ int __pthread_mutex_trylock_owner(pthread_mutex_t *m)
        pthread_t self = __pthread_self();
        int tid = self->tid;
 
-       if (type >= 4) {
-               if (!self->robust_list.off)
-                       __syscall(SYS_set_robust_list,
-                               &self->robust_list, 3*sizeof(long));
+       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;
@@ -23,21 +20,28 @@ int __pthread_mutex_trylock_owner(pthread_mutex_t *m)
                return 0;
        }
 
-       if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, old, tid)!=old)
-               return EBUSY;
-
-       if (type < 4) return 0;
+       self->robust_list.pending = &m->_m_next;
 
-       if (type >= 8) {
-               m->_m_lock = 0;
-               return ENOTRECOVERABLE;
+       if ((own && (!(own & 0x40000000) || !(type & 4)))
+           || a_cas(&m->_m_lock, old, tid) != old) {
+               self->robust_list.pending = 0;
+               return EBUSY;
        }
+
        m->_m_next = self->robust_list.head;
        m->_m_prev = &self->robust_list.head;
        if (self->robust_list.head)
                self->robust_list.head[-1] = &m->_m_next;
        self->robust_list.head = &m->_m_next;
        self->robust_list.pending = 0;
+
+       if (type < 4) return 0;
+
+       if (type >= 8) {
+               m->_m_lock = 0;
+               return ENOTRECOVERABLE;
+       }
+
        if (own) {
                m->_m_count = 0;
                m->_m_type += 8;