Index: pthread_mutex.c
===================================================================
RCS file: /cvsroot/src/lib/libpthread/pthread_mutex.c,v
retrieving revision 1.66
diff -u -r1.66 pthread_mutex.c
--- pthread_mutex.c	13 Jan 2020 18:22:56 -0000	1.66
+++ pthread_mutex.c	27 Jan 2020 23:05:29 -0000
@@ -197,6 +197,9 @@
 	if (__predict_false(__uselibcstub))
 		return __libc_mutex_lock_stub(ptm);
 
+	pthread__error(EINVAL, "Dead mutex",
+	    ptm->ptm_magic != _PT_MUTEX_MAGIC);
+
 	self = pthread__self();
 	val = atomic_cas_ptr(&ptm->ptm_owner, NULL, self);
 	if (__predict_true(val == NULL)) {
@@ -214,6 +217,9 @@
 	pthread_t self;
 	void *val;
 
+	pthread__error(EINVAL, "Dead mutex",
+	    ptm->ptm_magic != _PT_MUTEX_MAGIC);
+
 	self = pthread__self();
 	val = atomic_cas_ptr(&ptm->ptm_owner, NULL, self);
 	if (__predict_true(val == NULL)) {
@@ -410,6 +416,9 @@
 	if (__predict_false(__uselibcstub))
 		return __libc_mutex_trylock_stub(ptm);
 
+	pthread__error(EINVAL, "Dead mutex",
+	    ptm->ptm_magic != _PT_MUTEX_MAGIC);
+
 	self = pthread__self();
 	val = atomic_cas_ptr(&ptm->ptm_owner, NULL, self);
 	if (__predict_true(val == NULL)) {
@@ -450,6 +459,9 @@
 	if (__predict_false(__uselibcstub))
 		return __libc_mutex_unlock_stub(ptm);
 
+	pthread__error(EINVAL, "Dead mutex",
+	    ptm->ptm_magic != _PT_MUTEX_MAGIC);
+
 #ifndef PTHREAD__ATOMIC_IS_MEMBAR
 	membar_exit();
 #endif
@@ -777,6 +789,10 @@
 int
 pthread_mutex_getprioceiling(const pthread_mutex_t *ptm, int *ceil) 
 {
+
+	pthread__error(EINVAL, "Dead mutex",
+	    ptm->ptm_magic != _PT_MUTEX_MAGIC);
+
 	*ceil = ptm->ptm_ceiling;
 	return 0;
 }
@@ -786,6 +802,9 @@
 {
 	int error;
 
+	pthread__error(EINVAL, "Dead mutex",
+	    ptm->ptm_magic != _PT_MUTEX_MAGIC);
+
 	error = pthread_mutex_lock(ptm);
 	if (error == 0) {
 		*old_ceil = ptm->ptm_ceiling;