Process pinning roots - port PR #142 (#192)

Port #142 to `dev`. Process both
transitively pinning roots, and non transitively pinning roots.

Author: qinsoon

.gitignore

@@ -1,4 +1,6 @@
 .idea/
 julia/*.o
 julia/*.dbj.obj
-.vscode
+.vscode
+mmtk/src/julia_types.rs
+

mmtk/src/julia_scanning.rs

@@ -162,7 +162,7 @@ pub unsafe fn scan_julia_object<SV: SlotVisitor<JuliaVMSlot>>(obj: Address, clos
 
             let ta = obj.to_ptr::<jl_task_t>();
 
-            mmtk_scan_gcstack(ta, closure);
+            mmtk_scan_gcstack(ta, closure, None);
 
             let layout = (*jl_task_type).layout;
             debug_assert!((*layout).fielddesc_type_custom() == 0);
@@ -373,9 +373,10 @@ unsafe fn mmtk_jl_genericmemory_data_owner_field_address(m: *const jl_genericmem
 //     mmtk_jl_genericmemory_data_owner_field_address(m).load::<*const mmtk_jl_value_t>()
 // }
 
-pub unsafe fn mmtk_scan_gcstack<EV: SlotVisitor<JuliaVMSlot>>(
+pub unsafe fn mmtk_scan_gcstack<'a, EV: SlotVisitor<JuliaVMSlot>>(
     ta: *const jl_task_t,
-    closure: &mut EV,
+    mut closure: &'a mut EV,
+    mut pclosure: Option<&'a mut EV>,
 ) {
     let stkbuf = (*ta).ctx.stkbuf;
     let copy_stack = (*ta).ctx.copy_stack_custom();
@@ -404,16 +405,28 @@ pub unsafe fn mmtk_scan_gcstack<EV: SlotVisitor<JuliaVMSlot>>(
         let s_nroots_addr = ::std::ptr::addr_of!((*s).nroots);
         let mut nroots = read_stack(Address::from_ptr(s_nroots_addr), offset, lb, ub);
         debug_assert!(nroots.as_usize() as u32 <= u32::MAX);
-        let mut nr = nroots >> 2;
+        let mut nr = nroots >> 3;
 
         loop {
+            // if the 'pin' bit on the root type is not set, must transitively pin
+            // and therefore use transitive pinning closure
+            let closure_to_use: &mut &mut EV = if (nroots.as_usize() & 4) == 0 {
+                &mut closure
+            } else {
+                // otherwise, use the pinning closure (if available)
+                match &mut pclosure {
+                    Some(c) => c,
+                    None => &mut closure,
+                }
+            };
+
             let rts = Address::from_mut_ptr(s).shift::<Address>(2);
             let mut i = 0;
             while i < nr {
                 if (nroots.as_usize() & 1) != 0 {
                     let slot = read_stack(rts.shift::<Address>(i as isize), offset, lb, ub);
                     let real_addr = get_stack_addr(slot, offset, lb, ub);
-                    process_slot(closure, real_addr);
+                    process_slot(*closure_to_use, real_addr);
                 } else {
                     let real_addr =
                         get_stack_addr(rts.shift::<Address>(i as isize), offset, lb, ub);
@@ -429,12 +442,12 @@ pub unsafe fn mmtk_scan_gcstack<EV: SlotVisitor<JuliaVMSlot>>(
 
                     // pointer is not malloced but function is native, so skip it
                     if gc_ptr_tag(slot, 1) {
-                        process_offset_slot(closure, real_addr, 1);
+                        process_offset_slot(*closure_to_use, real_addr, 1);
                         i += 2;
                         continue;
                     }
 
-                    process_slot(closure, real_addr);
+                    process_slot(*closure_to_use, real_addr);
                 }
 
                 i += 1;
@@ -450,7 +463,7 @@ pub unsafe fn mmtk_scan_gcstack<EV: SlotVisitor<JuliaVMSlot>>(
             let s_nroots_addr = ::std::ptr::addr_of!((*s).nroots);
             let new_nroots = read_stack(Address::from_ptr(s_nroots_addr), offset, lb, ub);
             nroots = new_nroots;
-            nr = nroots >> 2;
+            nr = nroots >> 3;
             continue;
         }
     }

mmtk/src/scanning.rs

@@ -53,14 +53,19 @@ impl Scanning<JuliaVM> for VMScanning {
         use mmtk::util::Address;
 
         let ptls: &mut _jl_tls_states_t = unsafe { std::mem::transmute(mutator.mutator_tls) };
-        let mut slot_buffer = SlotBuffer { buffer: vec![] }; // need to be tpinned as they're all from the shadow stack
+        let mut tpinning_slot_buffer = SlotBuffer { buffer: vec![] }; // need to be transitively pinned
+        let mut pinning_slot_buffer = SlotBuffer { buffer: vec![] }; // roots from the shadow stack that we know that do not need to be transitively pinned
         let mut node_buffer = vec![];
 
         // Scan thread local from ptls: See gc_queue_thread_local in gc.c
         let mut root_scan_task = |task: *const _jl_task_t, task_is_root: bool| {
             if !task.is_null() {
                 unsafe {
-                    crate::julia_scanning::mmtk_scan_gcstack(task, &mut slot_buffer);
+                    crate::julia_scanning::mmtk_scan_gcstack(
+                        task,
+                        &mut tpinning_slot_buffer,
+                        Some(&mut pinning_slot_buffer),
+                    );
                 }
                 if task_is_root {
                     // captures wrong root nodes before creating the work
@@ -136,13 +141,20 @@ impl Scanning<JuliaVM> for VMScanning {
 
         // Push work
         const CAPACITY_PER_PACKET: usize = 4096;
-        for tpinning_roots in slot_buffer
+        for tpinning_roots in tpinning_slot_buffer
             .buffer
             .chunks(CAPACITY_PER_PACKET)
             .map(|c| c.to_vec())
         {
             factory.create_process_tpinning_roots_work(tpinning_roots);
         }
+        for pinning_roots in pinning_slot_buffer
+            .buffer
+            .chunks(CAPACITY_PER_PACKET)
+            .map(|c| c.to_vec())
+        {
+            factory.create_process_pinning_roots_work(pinning_roots);
+        }
         for nodes in node_buffer.chunks(CAPACITY_PER_PACKET).map(|c| c.to_vec()) {
             factory.create_process_pinning_roots_work(nodes);
         }