diff --git a/share/man/man3/pthread_condattr.3 b/share/man/man3/pthread_condattr.3
--- a/share/man/man3/pthread_condattr.3
+++ b/share/man/man3/pthread_condattr.3
@@ -112,6 +112,10 @@
 The condition variable it is attached to may be accessed by
 threads in processes other than the one that created the object.
 .El
+See
+.Xr libthr 3
+for details of the implementation of the shared condition variables,
+and their existing limitations.
 .Sh RETURN VALUES
 If successful, these functions return 0.
 Otherwise, an error number is returned to indicate the error.
@@ -154,7 +158,8 @@
 .El
 .Sh SEE ALSO
 .Xr pthread_cond_init 3 ,
-.Xr pthread_cond_timedwait 3
+.Xr pthread_cond_timedwait 3 ,
+.Xr libthr 3
 .Sh STANDARDS
 The
 .Fn pthread_condattr_init
diff --git a/share/man/man3/pthread_mutexattr.3 b/share/man/man3/pthread_mutexattr.3
--- a/share/man/man3/pthread_mutexattr.3
+++ b/share/man/man3/pthread_mutexattr.3
@@ -132,6 +132,30 @@
 .El
 .Pp
 The
+.Fn pthread_mutexattr_setpshared
+function will set the process-shared attribute of
+.Fa attr
+to the value specified in
+.Fa pshared .
+The argument
+.Fa pshared
+may have one of the following values:
+.Bl -tag -width ".Dv PTHREAD_PROCESS_PRIVATE"
+.It Dv PTHREAD_PROCESS_PRIVATE
+The mutex may only be used by threads in the same process as the one
+that created the object.
+.It Dv PTHREAD_PROCESS_SHARED
+The mutex may be used by
+threads in processes other than the one that created the object,
+assuming other processes have access to the memory where the mutex
+was allocated.
+.El
+See
+.Xr libthr 3
+for details of the implementation of the shared mutexes,
+and their existing limitations.
+.Pp
+The
 .Fn pthread_mutexattr_setrobust
 function specifies robustness attribute of the mutex.
 Possible values for the
@@ -314,7 +338,8 @@
 .Fa attr .
 .El
 .Sh SEE ALSO
-.Xr pthread_mutex_init 3
+.Xr pthread_mutex_init 3 ,
+.Xr libthr 3
 .Sh STANDARDS
 The
 .Fn pthread_mutexattr_init