diff --git a/ChangeLog b/ChangeLog
index 6f4a9968f7..ac969db2fa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Apr 12 17:13:22 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* thread.c (mutex_try_lock): check and set owner thread.
+
+	* thread_pthread.ci: fix to show error code in error message.
+
 Thu Apr 12 17:11:54 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* eval.c (rb_rescue2): restore cfp ([ruby-dev:30582]).
diff --git a/thread.c b/thread.c
index 68fcf06294..8373318a9e 100644
--- a/thread.c
+++ b/thread.c
@@ -2138,7 +2138,12 @@ mutex_try_lock(VALUE self)
     mutex_t *mutex;
     GetMutexVal(self, mutex);
 
+    if (mutex->th == GET_THREAD()) {
+	rb_raise(rb_eThreadError, "deadlock; recursive locking");
+    }
+
     if (native_mutex_trylock(&mutex->lock) != EBUSY) {
+	mutex->th = GET_THREAD();
 	return Qtrue;
     }
     else {
diff --git a/thread_pthread.ci b/thread_pthread.ci
index 34bb5362b9..43dac0be5a 100644
--- a/thread_pthread.ci
+++ b/thread_pthread.ci
@@ -48,16 +48,18 @@ native_mutex_trylock(pthread_mutex_t *lock)
 void
 native_mutex_initialize(pthread_mutex_t *lock)
 {
-    if (pthread_mutex_init(lock, 0) != 0) {
-	rb_bug("native_mutex_initialize return non-zero");
+    int r = pthread_mutex_init(lock, 0);
+    if (r != 0) {
+	rb_bug("native_mutex_initialize return non-zero: %d", r);
     }
 }
 
 void
 native_mutex_destroy(pthread_mutex_t *lock)
 {
-    if (pthread_mutex_destroy(lock) != 0) {
-	rb_bug("native_mutex_destroy return non-zero");
+    int r = pthread_mutex_destroy(lock);
+    if (r != 0) {
+	rb_bug("native_mutex_destroy return non-zero: %d", r);
     }
 }