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Don't check stack for moved after compaction

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We don't need to check stack for moved objects after compaction because
the mutator cannot run between marking the stack and the end of
compaction. However, the stack may have moved objects leftover from
marking and sweeping phases. This means that their pages will be
invalidated and all objects moved back. We don't need to move these
objects back.

This also fixes the issue on Windows where some compaction tests
sometimes fail due to the page of the object being invalidated.
This commit is contained in:
Peter Zhu 2023-08-03 10:35:44 -04:00
parent 6b570ff2c0
commit 4b45b2764b
Notes: git 2023-08-04 13:14:17 +00:00 
Merged: https://github.com/ruby/ruby/pull/8166
1 changed files with 0 additions and 44 deletions
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44
gc.c
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@ -5375,43 +5375,6 @@ install_handlers(void)
}
#endif
static void
revert_stack_objects(VALUE stack_obj, void *ctx)
{
rb_objspace_t * objspace = (rb_objspace_t*)ctx;
if (BUILTIN_TYPE(stack_obj) == T_MOVED) {
/* For now we'll revert the whole page if the object made it to the
* stack. I think we can change this to move just the one object
* back though */
invalidate_moved_page(objspace, GET_HEAP_PAGE(stack_obj));
}
}
static void
revert_machine_stack_references(rb_objspace_t *objspace, VALUE v)
{
if (is_pointer_to_heap(objspace, (void *)v)) {
if (BUILTIN_TYPE(v) == T_MOVED) {
/* For now we'll revert the whole page if the object made it to the
* stack. I think we can change this to move just the one object
* back though */
invalidate_moved_page(objspace, GET_HEAP_PAGE(v));
}
}
}
static void each_machine_stack_value(const rb_execution_context_t *ec, void (*cb)(rb_objspace_t *, VALUE));
static void
check_stack_for_moved(rb_objspace_t *objspace)
{
rb_execution_context_t *ec = GET_EC();
rb_vm_t *vm = rb_ec_vm_ptr(ec);
rb_vm_each_stack_value(vm, revert_stack_objects, (void*)objspace);
each_machine_stack_value(ec, revert_machine_stack_references);
}
static void
gc_compact_finish(rb_objspace_t *objspace)
{
@ -5423,13 +5386,6 @@ gc_compact_finish(rb_objspace_t *objspace)
uninstall_handlers();
/* The mutator is allowed to run during incremental sweeping. T_MOVED
* objects can get pushed on the stack and when the compaction process
* finishes up, it may remove the read barrier before anything has a
* chance to read from the T_MOVED address. To fix this, we scan the stack
* then revert any moved objects that made it to the stack. */
check_stack_for_moved(objspace);
gc_update_references(objspace);
objspace->profile.compact_count++;