diff --git a/ChangeLog b/ChangeLog
index 187157498c..c4cebd3405 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+Fri Nov  6 18:33:47 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* vm_insnhelper.c (vm_push_frame): add CHECK_STACK_OVERFLOW.
+	  [ruby-dev:39592]
+
+	* eval.c (rb_longjmp): add 1 level backtrace for sysstack_error
+	  without calling any method to prevent further stack overflow.
+
+	* eval.c (make_exception): don't call #exception for
+	  sysstack_error to prevent stack overflow.
+
+	* proc.c (Init_Proc): don't freeze sysstack_error.
+
+	* eval.c (rb_longjmp): move reentrant check after exception
+	  preparation.
+
 Fri Nov  6 17:13:45 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/mkmf.rb (create_header): split the line by tabs.
diff --git a/eval.c b/eval.c
index f33d80360a..c3bde6b9e4 100644
--- a/eval.c
+++ b/eval.c
@@ -358,12 +358,6 @@ rb_longjmp(int tag, volatile VALUE mesg)
     const char *file;
     volatile int line = 0;
 
-    if (rb_threadptr_set_raised(th)) {
-	th->errinfo = exception_error;
-	rb_threadptr_reset_raised(th);
-	JUMP_TAG(TAG_FATAL);
-    }
-
     if (NIL_P(mesg))
 	mesg = th->errinfo;
     if (NIL_P(mesg)) {
@@ -373,13 +367,19 @@ rb_longjmp(int tag, volatile VALUE mesg)
     file = rb_sourcefile();
     if (file) line = rb_sourceline();
     if (file && !NIL_P(mesg)) {
-	at = get_backtrace(mesg);
-	if (NIL_P(at)) {
-	    at = rb_make_backtrace();
-	    if (OBJ_FROZEN(mesg)) {
-		mesg = rb_obj_dup(mesg);
+	if (mesg == sysstack_error) {
+	    at = rb_enc_sprintf(rb_usascii_encoding(), "%s:%d", file, line);
+	    rb_iv_set(mesg, "bt", at);
+	}
+	else {
+	    at = get_backtrace(mesg);
+	    if (NIL_P(at)) {
+		at = rb_make_backtrace();
+		if (OBJ_FROZEN(mesg)) {
+		    mesg = rb_obj_dup(mesg);
+		}
+		set_backtrace(mesg, at);
 	    }
-	    set_backtrace(mesg, at);
 	}
     }
     if (!NIL_P(mesg)) {
@@ -414,6 +414,12 @@ rb_longjmp(int tag, volatile VALUE mesg)
 	}
     }
 
+    if (rb_threadptr_set_raised(th)) {
+	th->errinfo = exception_error;
+	rb_threadptr_reset_raised(th);
+	JUMP_TAG(TAG_FATAL);
+    }
+
     rb_trap_restore_mask();
 
     if (tag != TAG_FATAL) {
@@ -520,6 +526,7 @@ make_exception(int argc, VALUE *argv, int isstr)
       case 3:
 	n = 1;
       exception_call:
+	if (argv[0] == sysstack_error) return argv[0];
 	CONST_ID(exception, "exception");
 	mesg = rb_check_funcall(argv[0], exception, n, argv+1);
 	if (mesg == Qundef) {
diff --git a/proc.c b/proc.c
index 468ca467be..daf8c673fe 100644
--- a/proc.c
+++ b/proc.c
@@ -2043,7 +2043,6 @@ Init_Proc(void)
     sysstack_error = rb_exc_new3(rb_eSysStackError,
 				 rb_obj_freeze(rb_str_new2("stack level too deep")));
     OBJ_TAINT(sysstack_error);
-    OBJ_FREEZE(sysstack_error);
 
     /* utility functions */
     rb_define_global_function("proc", rb_block_proc, 0);
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 5b965d2157..7974a75cd8 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -26,9 +26,11 @@ vm_push_frame(rb_thread_t * th, const rb_iseq_t * iseq,
 	      const VALUE *pc, VALUE *sp, VALUE *lfp,
 	      int local_size)
 {
-    rb_control_frame_t * const cfp = th->cfp = th->cfp - 1;
+    rb_control_frame_t * const cfp = th->cfp - 1;
     int i;
 
+    CHECK_STACK_OVERFLOW(th->cfp, local_size);
+    th->cfp = cfp;
     /* setup vm value stack */
 
     /* nil initialize */