nobu	2014-06-23 11:11:31 +0900 (Mon, 23 Jun 2014)

  New Revision: 46499

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=46499

  Log:
    signal.c: drop dangerous tag
    
    * signal.c (check_stack_overflow): drop the last tag too close to
      the fault page, to get rid of stack overflow deadlock.
      [Bug #9971]

  Modified files:
    trunk/ChangeLog
    trunk/signal.c
Index: ChangeLog
===================================================================
--- ChangeLog	(revision 46498)
+++ ChangeLog	(revision 46499)
@@ -1,3 +1,9 @@ https://github.com/ruby/ruby/blob/trunk/ChangeLog#L1
+Mon Jun 23 11:11:16 2014  Nobuyoshi Nakada  <nobu@r...>
+
+	* signal.c (check_stack_overflow): drop the last tag too close to
+	  the fault page, to get rid of stack overflow deadlock.
+	  [Bug #9971]
+
 Sun Jun 22 09:11:15 2014  NARUSE, Yui  <naruse@r...>
 
 	* lib/uri/generic.rb: remove registry.
Index: signal.c
===================================================================
--- signal.c	(revision 46498)
+++ signal.c	(revision 46499)
@@ -738,6 +738,12 @@ check_stack_overflow(const uintptr_t add https://github.com/ruby/ruby/blob/trunk/signal.c#L738
      * the fault page can be the next. */
     if (sp_page == fault_page || sp_page == fault_page + 1) {
 	rb_thread_t *th = ruby_current_thread;
+	if ((uintptr_t)th->tag->buf / pagesize == sp_page) {
+	    /* drop the last tag if it is close to the fault,
+	     * otherwise it can cause stack overflow again at the same
+	     * place. */
+	    th->tag = th->tag->prev;
+	}
 	ruby_thread_stack_overflow(th);
     }
 }

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