diff --git a/ChangeLog b/ChangeLog
index dc11d96b53..cc893f3e76 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Nov  9 11:36:53 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* thread_pthread.c (gvl_yield): don't prevent concurrent sched_yield().
+	  [Bug #5130] [ruby-core:38647]
+
 Wed Nov  9 23:20:22 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c (rb_update_max_fd): fstat(2) can fail with other than
diff --git a/thread_pthread.c b/thread_pthread.c
index 7d03bcc561..7fa8e95ebd 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -109,16 +109,13 @@ gvl_yield(rb_vm_t *vm, rb_thread_t *th)
 	goto acquire;
     }
 
-    vm->gvl.wait_yield = 1;
-
-    if (vm->gvl.waiting > 0)
-	vm->gvl.need_yield = 1;
-
-    if (vm->gvl.need_yield) {
+    if (vm->gvl.waiting > 0) {
 	/* Wait until another thread task take GVL. */
-	while (vm->gvl.need_yield) {
+	vm->gvl.need_yield = 1;
+	vm->gvl.wait_yield = 1;
+	while (vm->gvl.need_yield)
 	    native_cond_wait(&vm->gvl.switch_cond, &vm->gvl.lock);
-	}
+	vm->gvl.wait_yield = 0;
     }
     else {
 	native_mutex_unlock(&vm->gvl.lock);
@@ -126,7 +123,6 @@ gvl_yield(rb_vm_t *vm, rb_thread_t *th)
 	native_mutex_lock(&vm->gvl.lock);
     }
 
-    vm->gvl.wait_yield = 0;
     native_cond_broadcast(&vm->gvl.switch_wait_cond);
   acquire:
     gvl_acquire_common(vm);