Pinning buffers; removing transitive pinning of global_roots_table; Pinning wr

Author: Luis Eduardo de Souza Amorim

src/gc-mmtk.c

@@ -510,19 +510,6 @@ static void add_node_to_roots_buffer(RootsWorkClosure* closure, RootsWorkBuffer*
     }
 }
 
-static void add_node_to_tpinned_roots_buffer(RootsWorkClosure* closure, RootsWorkBuffer* buf, size_t* buf_len, void* root) {
-    if (root == NULL)
-        return;
-
-    buf->ptr[*buf_len] = root;
-    *buf_len += 1;
-    if (*buf_len >= buf->cap) {
-        RootsWorkBuffer new_buf = (closure->report_tpinned_nodes_func)(buf->ptr, *buf_len, buf->cap, closure->data, true);
-        *buf = new_buf;
-        *buf_len = 0;
-    }
-}
-
 // staticdata_utils.c
 extern jl_array_t *internal_methods;
 extern jl_array_t *newly_inferred;
@@ -824,15 +811,8 @@ JL_DLLEXPORT void jl_gc_scan_vm_specific_roots(RootsWorkClosure* closure)
     // add_node_to_roots_buffer(closure, &buf, &len, cmpswap_names);
     // add_node_to_roots_buffer(closure, &buf, &len, precompile_field_replace);
 
-    // jl_global_roots_table must be transitively pinned
-    // FIXME: We need to remove transitive pinning of global roots. Otherwise they may pin most of the objects in the heap.
-    RootsWorkBuffer tpinned_buf = (closure->report_tpinned_nodes_func)((void**)0, 0, 0, closure->data, true);
-    size_t tpinned_len = 0;
-    add_node_to_tpinned_roots_buffer(closure, &tpinned_buf, &tpinned_len, jl_global_roots_list);
-    add_node_to_tpinned_roots_buffer(closure, &tpinned_buf, &tpinned_len, jl_global_roots_keyset);
     // Push the result of the work.
     (closure->report_nodes_func)(buf.ptr, len, buf.cap, closure->data, false);
-    (closure->report_tpinned_nodes_func)(tpinned_buf.ptr, tpinned_len, tpinned_buf.cap, closure->data, false);
 }
 
 JL_DLLEXPORT void jl_gc_scan_julia_exc_obj(void* obj_raw, void* closure, ProcessSlotFn process_slot) {
@@ -1086,6 +1066,7 @@ JL_DLLEXPORT jl_weakref_t *jl_gc_new_weakref_th(jl_ptls_t ptls, jl_value_t *valu
 {
     jl_weakref_t *wr = (jl_weakref_t*)jl_gc_alloc(ptls, sizeof(void*), jl_weakref_type);
     wr->value = value;  // NOTE: wb not needed here
+    OBJ_PIN(wr)
     // Note: we are using MMTk's weak ref processing. If we switch to Julia's weak ref processing,
     // we need to make sure the value and the weak ref won't be moved (e.g. pin them)
     mmtk_add_weak_candidate(wr);

src/julia_internal.h

@@ -585,7 +585,11 @@ JL_DLLEXPORT uintptr_t jl_get_buff_tag(void) JL_NOTSAFEPOINT;
 typedef void jl_gc_tracked_buffer_t; // For the benefit of the static analyzer
 STATIC_INLINE jl_gc_tracked_buffer_t *jl_gc_alloc_buf(jl_ptls_t ptls, size_t sz)
 {
-    return jl_gc_alloc(ptls, sz, (void*)jl_buff_tag);
+    jl_gc_tracked_buffer_t *buf = jl_gc_alloc(ptls, sz, (void*)jl_buff_tag);
+    // FIXME: we might not need to pin buffers since the introduction of jl_genericmemory_t objects
+    // but removing the pin below will currently fail an assertion in the binding
+    OBJ_PIN(buf);
+    return buf;
 }
 
 jl_value_t *jl_permbox8(jl_datatype_t *t, uintptr_t tag, uint8_t x);

src/llvm-late-gc-lowering-stock.cpp

@@ -10,4 +10,4 @@ Value* LateLowerGCFrame::lowerGCAllocBytesLate(CallInst *target, Function &F)
 
 void LateLowerGCFrame::CleanupGCPreserve(Function &F, CallInst *CI, Value *callee, Type *T_size) {
     // Do nothing for the stock GC
-}
+}