merge revision(s) 64589,64593: [Backport #15041]

	cont.c: set th->root_fiber to current fiber at fork

	Otherwise, th->root_fiber can point to an invalid Fiber,
	because Fibers do not live across fork.  So consider
	whatever Fiber is running the root fiber.

	[ruby-core:88723] [Bug #15041]

	cont.c (rb_fiber_atfork): th->root_fiber may not exist

	Otherwise, bootstraptest/test_fork.rb fails with -DVM_CHECK_MODE=2

	[Bug #15041]

	Fixes: r64589 "cont.c: set th->root_fiber to current fiber at fork"

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@66968 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 14 insertions, 0 deletions

diff --git a/cont.c b/cont.c
index c56ea0f6e6..8d54b369a6 100644
--- a/cont.c
+++ b/cont.c
@@ -1660,6 +1660,20 @@ rb_fiber_s_current(VALUE klass)
 
 
 
+#ifdef HAVE_WORKING_FORK
+void
+rb_fiber_atfork(rb_thread_t *th)
+{
+    if (th->root_fiber) {
+        if (&th->root_fiber->cont.saved_ec != th->ec) {
+            th->root_fiber = th->ec->fiber_ptr;
+            th->root_fiber->cont.type = ROOT_FIBER_CONTEXT;
+        }
+        th->root_fiber->prev = 0;
+    }
+}
+#endif
+
 /*
  *  Document-class: FiberError
  *