merge revision(s) r46495,r46499: [Backport ruby#9971]

	signal.c: no cfunc frame at stack overflow

	* signal.c (check_stack_overflow): avoid pushing a cfunc frame,
  trying to fix stack overflow deadlock.
	* signal.c (check_stack_overflow): drop the last tag too close to
	  the fault page, to get rid of stack overflow deadlock.
	  [Bug ruby#9971]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@47597 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Author: nagachika

ChangeLog

@@ -1,3 +1,9 @@
+Mon Sep 15 23:12:47 2014  Nobuyoshi Nakada  <[email protected]>
+
+	* signal.c (check_stack_overflow): drop the last tag too close to
+	  the fault page, to get rid of stack overflow deadlock.
+	  [Bug #9971]
+
 Mon Sep 15 22:34:39 2014  Natalie Weizenbaum  <[email protected]>
 
 	* ext/pathname/lib/pathname.rb (SAME_PATHS):

signal.c

@@ -711,15 +711,22 @@ check_stack_overflow(const uintptr_t addr, const ucontext_t *ctx)
     /* SP in ucontext is not decremented yet when `push` failed, so
      * the fault page can be the next. */
     if (sp_page == fault_page || sp_page == fault_page + 1) {
-	ruby_thread_stack_overflow(GET_THREAD());
+	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);
     }
 }
 #else
 static void
 check_stack_overflow(const void *addr)
 {
     int ruby_stack_overflowed_p(const rb_thread_t *, const void *);
-    rb_thread_t *th = GET_THREAD();
+    rb_thread_t *th = ruby_current_thread;
     if (ruby_stack_overflowed_p(th, addr)) {
 	ruby_thread_stack_overflow(th);
     }

version.h

@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.1.2"
 #define RUBY_RELEASE_DATE "2014-09-15"
-#define RUBY_PATCHLEVEL 240
+#define RUBY_PATCHLEVEL 241
 
 #define RUBY_RELEASE_YEAR 2014
 #define RUBY_RELEASE_MONTH 9