implement robust mutexes

some of this code should be cleaned up, e.g. using macros for some of
the bit flags, masks, etc. nonetheless, the code is believed to be
working and correct at this point.

1 files changed, 35 insertions, 3 deletions

diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c
index de57ff9e..f48aaade 100644
--- a/src/thread/pthread_mutex_trylock.c
+++ b/src/thread/pthread_mutex_trylock.c
@@ -3,19 +3,51 @@
 int pthread_mutex_trylock(pthread_mutex_t *m)
 {
 	int tid;
+	int own;
+	pthread_t self;
 
 	if (m->_m_type == PTHREAD_MUTEX_NORMAL)
 		return (m->_m_lock || a_swap(&m->_m_lock, 1)) ? EBUSY : 0;
 
-	tid = pthread_self()->tid;
+	self = pthread_self();
+	tid = self->tid | 0x80000000;
 
-	if (m->_m_lock == tid && m->_m_type == PTHREAD_MUTEX_RECURSIVE) {
+	if (m->_m_type >= 4) {
+		if (!self->robust_list.off)
+			syscall2(__NR_set_robust_list,
+				(long)&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;
+	}
+
+	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 (m->_m_lock || a_cas(&m->_m_lock, 0, tid)) return EBUSY;
+	own = m->_m_lock;
+	if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, own, tid)!=own)
+		return EBUSY;
+
 	m->_m_count = 1;
+
+	if (m->_m_type < 4) return 0;
+
+	if (m->_m_type >= 8) {
+		m->_m_lock = 0;
+		return ENOTRECOVERABLE;
+	}
+	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 (own) {
+		m->_m_type += 8;
+		return EOWNERDEAD;
+	}
+
 	return 0;
 }