Use distributed refcounts to free VMAs

This eliminates all reports of unexpected sharing except a few cases of honest-to-goodness memory reuse.

Use distributed refcounts to free VMAs
2db6c3ef · Austin Clements · f08c7712 · 2db6c3ef · 2db6c3ef
--- a/include/radix.hh
+++ b/include/radix.hh
@@ -147,18 +147,11 @@ private:
 };

 class radix_elem : public rcu_freed {
- private:
-  std::atomic<u64> ref_;
-
 public:
-  radix_elem() : rcu_freed("radix_elem"), ref_(0) {}
+  radix_elem() : rcu_freed("radix_elem") {}
  virtual ~radix_elem() {}
-  void decref(u64 delta = 1) {
-    if ((ref_ -= delta) == 0) {
-      gc_delayed(this);
-    }
-  }
-  void incref(u64 delta = 1) { ref_ += delta; }
+  virtual void decref(u64 delta = 1) = 0;
+  virtual void incref(u64 delta = 1) = 0;
 };

 struct radix_node {

--- a/include/vm.hh
+++ b/include/vm.hh
@@ -6,6 +6,7 @@
 #include "cpputil.hh"
 #include "hwvm.hh"
 #include "uwq.hh"
+#include "distref.hh"

 #define VM_CRANGE 0
 #define VM_RADIX  1
@@ -53,7 +54,7 @@ struct vma
  : public range
 #endif
 #if VM_RADIX
-  : public radix_elem
+  : public radix_elem, public distributed_refcnt
 #endif
 {
  const uptr vma_start;        // start of mapping
@@ -64,8 +65,27 @@ struct vma
  vma(vmap *vmap, uptr start, uptr end, enum vmatype vtype, vmnode *vmn);
  ~vma();

+  NEW_DELETE_OPS(vma);
+
  virtual void do_gc() { delete this; }
-  NEW_DELETE_OPS(vma)
+
+#if VM_RADIX
+  void decref(u64 delta)
+  {
+    distref_dec(delta);
+  }
+
+  void incref(u64 delta)
+  {
+    distref_inc(delta);
+  }
+
+private:
+  void distref_free()
+  {
+    gc_delayed(this);
+  }
+#endif
 };

 class print_stream;