release VM stack properly.

* cont.c: r55766 change the handling method of Fiber's VM stack.
  Resumed Fiber points NULL as VM stack and running Thread has
  responsibility to manage it (marking and releasing).

  However, thread_start_func_2()@thread.c and thread_free()@vm.c
  doesn't free the VM stack if corresponding root Fiber is exist.
  This causes memory leak. [Bug #13772]

* cont.c (root_fiber_alloc): fib->cont.saved_thread.ec.stack should be NULL
  because running thread has responsibility to manage this stack.

* vm.c (rb_thread_recycle_stack_release): assert given stack is not NULL
  (callers should care it).


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59462 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

cont.c

@@ -1288,6 +1288,7 @@ root_fiber_alloc(rb_thread_t *th)
     rb_fiber_t *fib;
     /* no need to allocate vm stack */
     fib = fiber_t_alloc(fiber_alloc(rb_cFiber));
+    fib->cont.saved_thread.ec.stack = NULL;
     fib->cont.type = ROOT_FIBER_CONTEXT;
 #if FIBER_USE_NATIVE
 #ifdef _WIN32

thread.c

@@ -694,10 +694,8 @@ thread_start_func_2(rb_thread_t *th, VALUE *stack_start, VALUE *register_stack_s
 	rb_threadptr_unlock_all_locking_mutexes(th);
 	rb_check_deadlock(th->vm);
 
-	if (!th->root_fiber) {
-	    rb_thread_recycle_stack_release(th->ec.stack);
-	    th->ec.stack = 0;
-	}
+	rb_thread_recycle_stack_release(th->ec.stack);
+	th->ec.stack = NULL;
     }
     native_mutex_lock(&th->vm->thread_destruct_lock);
     /* make sure vm->running_thread never point me after this point.*/

vm.c

@@ -2330,7 +2330,7 @@ static int thread_recycle_stack_count = 0;
 static VALUE *
 thread_recycle_stack(size_t size)
 {
-    if (thread_recycle_stack_count) {
+    if (thread_recycle_stack_count > 0) {
 	/* TODO: check stack size if stack sizes are variable */
 	return thread_recycle_stack_slot[--thread_recycle_stack_count];
     }
@@ -2346,6 +2346,8 @@ thread_recycle_stack(size_t size)
 void
 rb_thread_recycle_stack_release(VALUE *stack)
 {
+    VM_ASSERT(stack != NULL);
+
 #if USE_THREAD_DATA_RECYCLE
     if (thread_recycle_stack_count < RECYCLE_MAX) {
 	thread_recycle_stack_slot[thread_recycle_stack_count++] = stack;
@@ -2429,8 +2431,9 @@ thread_free(void *ptr)
     rb_thread_t *th = ptr;
     RUBY_FREE_ENTER("thread");
 
-    if (!th->root_fiber) {
-	RUBY_FREE_UNLESS_NULL(th->ec.stack);
+    if (th->ec.stack != NULL) {
+	rb_thread_recycle_stack_release(th->ec.stack);
+	th->ec.stack = NULL;
     }
 
     if (th->locking_mutex != Qfalse) {