Update for mmtk/mmtk-core#817.

Author: wks

mmtk/src/abi.rs

@@ -337,8 +337,10 @@ pub struct RubyUpcalls {
     pub resume_mutators: extern "C" fn(tls: VMWorkerThread),
     pub block_for_gc: extern "C" fn(tls: VMMutatorThread),
     pub number_of_mutators: extern "C" fn() -> usize,
-    pub reset_mutator_iterator: extern "C" fn(),
-    pub get_next_mutator: extern "C" fn() -> *mut RubyMutator,
+    pub get_mutators: extern "C" fn(
+        visit_mutator: extern "C" fn(*mut RubyMutator, *mut libc::c_void),
+        data: *mut libc::c_void,
+    ),
     pub scan_vm_specific_roots: extern "C" fn(),
     pub scan_thread_roots: extern "C" fn(),
     pub scan_thread_root: extern "C" fn(mutator_tls: VMMutatorThread, worker_tls: VMWorkerThread),

mmtk/src/active_plan.rs

@@ -1,3 +1,5 @@
+use std::marker::PhantomData;
+
 use crate::mmtk;
 use crate::upcalls;
 use crate::Ruby;
@@ -25,16 +27,39 @@ impl ActivePlan<Ruby> for VMActivePlan {
         unimplemented!()
     }
 
-    fn reset_mutator_iterator() {
-        (upcalls().reset_mutator_iterator)();
+    fn mutators<'a>() -> Box<dyn Iterator<Item = &'a mut Mutator<Ruby>> + 'a> {
+        let mut mutators = vec![];
+        (upcalls().get_mutators)(
+            add_mutator_to_vec,
+            &mut mutators as *mut Vec<*mut Mutator<Ruby>> as _,
+        );
+
+        Box::new(RubyMutatorIterator {
+            mutators,
+            cursor: 0,
+            phantom_data: PhantomData,
+        })
     }
+}
+
+extern "C" fn add_mutator_to_vec(mutator: *mut Mutator<Ruby>, mutators: *mut libc::c_void) {
+    let mutators = unsafe { &mut *(mutators as *mut Vec<*mut Mutator<Ruby>>) };
+    mutators.push(mutator);
+}
+
+struct RubyMutatorIterator<'a> {
+    mutators: Vec<*mut Mutator<Ruby>>,
+    cursor: usize,
+    phantom_data: PhantomData<&'a ()>,
+}
+
+impl<'a> Iterator for RubyMutatorIterator<'a> {
+    type Item = &'a mut Mutator<Ruby>;
 
-    fn get_next_mutator() -> Option<&'static mut Mutator<Ruby>> {
-        let ptr = (upcalls().get_next_mutator)();
-        if ptr.is_null() {
-            None
-        } else {
-            Some(unsafe { &mut (*ptr) as &'static mut Mutator<Ruby> })
-        }
+    fn next(&mut self) -> Option<Self::Item> {
+        self.mutators.get(self.cursor).cloned().map(|mutator_ptr| {
+            self.cursor += 1;
+            unsafe { &mut *mutator_ptr as _ }
+        })
     }
 }