Prevent the stack from being marked twice

This commit prevents the stack from being marked twice: once via the
Fiber, and once via the Thread.  It introduces an assertion to assert
that the ec on the thread is the same as the ec on the Fiber being
marked via the thread.

1 files changed, 1 insertions, 2 deletions

diff --git a/vm.c b/vm.c
index c2dda3fdc4..4538c8b607 100644
--- a/vm.c
+++ b/vm.c
@@ -3138,8 +3138,7 @@ thread_mark(void *ptr)
     RUBY_MARK_UNLESS_NULL(th->top_wrapper);
     if (th->root_fiber) rb_fiber_mark_self(th->root_fiber);
 
-    /* Ensure EC stack objects are pinned */
-    rb_execution_context_mark(th->ec);
+    RUBY_ASSERT(th->ec == rb_fiberptr_get_ec(th->ec->fiber_ptr));
     RUBY_MARK_UNLESS_NULL(th->stat_insn_usage);
     RUBY_MARK_UNLESS_NULL(th->last_status);
     RUBY_MARK_UNLESS_NULL(th->locking_mutex);