From 014c1768ae7d6445631029d110d316ced2028fab Mon Sep 17 00:00:00 2001
From: Yi Lin <qinsoon@gmail.com>
Date: Fri, 29 Nov 2024 15:31:10 +1300
Subject: [PATCH] Deal with GC preserve stacks (#191)

This PR ports https://github.com/mmtk/mmtk-julia/pull/156 to `dev`.
---
 .gitignore                 |  1 -
 mmtk/Cargo.toml            |  2 +-
 mmtk/src/julia_scanning.rs | 57 ++++++++++++++++++++++++++++++++++++++
 mmtk/src/scanning.rs       |  4 +++
 4 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 02fc026..6707474 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,4 +3,3 @@ julia/*.o
 julia/*.dbj.obj
 .vscode
 mmtk/src/julia_types.rs
-
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index 5acf7bd..12e24c2 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -11,7 +11,7 @@ edition = "2018"
 [package.metadata.julia]
 # Our CI matches the following line and extract mmtk/julia. If this line is updated, please check ci yaml files and make sure it works.
 julia_repo = "https://github.com/mmtk/julia.git"
-julia_version = "97828e0a7febe174fb6f0e569bd07509d977e446"
+julia_version = "b4c8f5d443730d91c34785186c373ed3118cc7aa"
 
 [lib]
 crate-type = ["cdylib"]
diff --git a/mmtk/src/julia_scanning.rs b/mmtk/src/julia_scanning.rs
index 7c76895..903a098 100644
--- a/mmtk/src/julia_scanning.rs
+++ b/mmtk/src/julia_scanning.rs
@@ -375,11 +375,68 @@ 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_gcpreserve_stack<'a, EV: SlotVisitor<JuliaVMSlot>>(
+    ta: *const jl_task_t,
+    closure: &'a mut EV,
+) {
+    // process transitively pinning stack
+    let mut s = (*ta).gcpreserve_stack;
+    let (offset, lb, ub) = (0 as isize, 0 as u64, u64::MAX);
+
+    if s != std::ptr::null_mut() {
+        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() <= u32::MAX as usize);
+        let mut nr = nroots >> 3;
+
+        loop {
+            let rts = Address::from_mut_ptr(s).shift::<Address>(2);
+            let mut i = 0;
+
+            while i < nr {
+                let real_addr = get_stack_addr(rts.shift::<Address>(i as isize), offset, lb, ub);
+
+                let slot = read_stack(rts.shift::<Address>(i as isize), offset, lb, ub);
+                use crate::julia_finalizer::gc_ptr_tag;
+                // malloced pointer tagged in jl_gc_add_quiescent
+                // skip both the next element (native function), and the object
+                if slot & 3usize == 3 {
+                    i += 2;
+                    continue;
+                }
+
+                // pointer is not malloced but function is native, so skip it
+                if gc_ptr_tag(slot, 1) {
+                    i += 2;
+                    continue;
+                }
+
+                process_slot(closure, real_addr);
+                i += 1;
+            }
+
+            let s_prev_address = ::std::ptr::addr_of!((*s).prev);
+            let sprev = read_stack(Address::from_ptr(s_prev_address), offset, lb, ub);
+            if sprev.is_zero() {
+                break;
+            }
+
+            s = sprev.to_mut_ptr::<jl_gcframe_t>();
+            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 >> 3;
+            continue;
+        }
+    }
+}
+
 pub unsafe fn mmtk_scan_gcstack<'a, EV: SlotVisitor<JuliaVMSlot>>(
     ta: *const jl_task_t,
     mut closure: &'a mut EV,
     mut pclosure: Option<&'a mut EV>,
 ) {
+    // process Julia's standard shadow (GC) stack
     let stkbuf = (*ta).ctx.stkbuf;
     let copy_stack = (*ta).ctx.copy_stack_custom();
 
diff --git a/mmtk/src/scanning.rs b/mmtk/src/scanning.rs
index 472c0d4..da2f348 100644
--- a/mmtk/src/scanning.rs
+++ b/mmtk/src/scanning.rs
@@ -61,6 +61,10 @@ impl Scanning<JuliaVM> for VMScanning {
         let mut root_scan_task = |task: *const _jl_task_t, task_is_root: bool| {
             if !task.is_null() {
                 unsafe {
+                    crate::julia_scanning::mmtk_scan_gcpreserve_stack(
+                        task,
+                        &mut tpinning_slot_buffer,
+                    );
                     crate::julia_scanning::mmtk_scan_gcstack(
                         task,
                         &mut tpinning_slot_buffer,