merge revision(s) 59462,59474: [Backport #13772]

	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).

	fix stack storing for root fibers.

	* cont.c (root_fiber_alloc): this function is called by fiber_current()
	  and fiber_store(). fiber_current() should clear VM stack information
	  in a fiber data because runnning thread knows stack information and has
	  responsibility to manage it. However fiber_store() requires to remain
	  VM stack information in a fiber data because the responsibility to manage
	  VM stack is moved to the Fiber from the Thread (and switch to another
	  fiber).

	* cont.c (root_fiber_alloc): save thread's fiber and root_fiber information.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@59516 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 6 insertions, 4 deletions

diff --git a/cont.c b/cont.c
index ab4f2bc830..c56ea0f6e6 100644
--- a/cont.c
+++ b/cont.c
@@ -575,6 +575,8 @@ cont_restore_thread(rb_context_t *cont)
     th->root_lep = sth->root_lep;
     th->root_svar = sth->root_svar;
     th->ensure_list = sth->ensure_list;
+    VM_ASSERT(th->stack != NULL);
+    VM_ASSERT(sth->status == THREAD_RUNNABLE);
 }
 
 #if FIBER_USE_NATIVE
@@ -1316,6 +1318,7 @@ root_fiber_alloc(rb_thread_t *th)
 #endif
     fib->status = RUNNING;
 
+    th->root_fiber = th->fiber = fib;
     return fib;
 }
 
@@ -1324,9 +1327,9 @@ fiber_current(void)
 {
     rb_thread_t *th = GET_THREAD();
     if (th->fiber == 0) {
-	/* save root */
 	rb_fiber_t *fib = root_fiber_alloc(th);
-	th->root_fiber = th->fiber = fib;
+	/* Running thread object has stack management responsibility */
+	fib->cont.saved_thread.stack = NULL;
     }
     return th->fiber;
 }
@@ -1367,9 +1370,8 @@ fiber_store(rb_fiber_t *next_fib, rb_thread_t *th)
 	cont_save_thread(&fib->cont, th);
     }
     else {
-	/* create current fiber */
+	/* create root fiber */
 	fib = root_fiber_alloc(th);
-	th->root_fiber = th->fiber = fib;
     }
 
 #if FIBER_USE_NATIVE