avoid crash on stupid but allowable usage of pthread_mutex_unlock

unlocking an unlocked mutex is not UB for robust or error-checking
mutexes, so we must avoid calling __pthread_self (which might crash
due to lack of thread-register initialization) until after checking
that the mutex is locked.

diff --git a/src/thread/pthread_mutex_unlock.c b/src/thread/pthread_mutex_unlock.c
index 5855db0..6c4d7f2 100644 (file)
--- a/src/thread/pthread_mutex_unlock.c
+++ b/src/thread/pthread_mutex_unlock.c
@@ -5,9 +5,11 @@ int pthread_mutex_unlock(pthread_mutex_t *m)
        pthread_t self;
 
        if (m->_m_type != PTHREAD_MUTEX_NORMAL) {
+               if (!m->_m_lock)
+                       return EPERM;
                self = __pthread_self();
                if ((m->_m_lock&0x1fffffff) != self->tid)
-                       return EPERM;
+                       return EPERM;
                if ((m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE && --m->_m_count)
                        return 0;
                if (m->_m_type >= 4) {