Some vm tweaks to help track down a bug in uwq, or one that uwq tickles

acdc33a2 · Silas Boyd-Wickizer · a10f9aa2 · acdc33a2 · acdc33a2
--- a/include/vm.hh
+++ b/include/vm.hh
@@ -20,7 +20,6 @@ enum vmntype { EAGER, ONDEMAND };
 struct vmnode {
  const u64 npages;
  atomic<char*> page[128];
-  atomic<u64> ref;
  const enum vmntype type;
  struct inode *const ip;
  const u64 offset;
@@ -30,11 +29,15 @@ struct vmnode {
         inode *i = 0, u64 off = 0, u64 s = 0);
  ~vmnode();
  void decref();
+  void incref();
+  u64 ref();
  int allocpg();
  vmnode* copy();

  int demand_load();
-  NEW_DELETE_OPS(vmnode)
+  NEW_DELETE_OPS(vmnode);
+private:
+  atomic<u64> ref_;
 };

 // A mapping of a chunk of an address space to

--- a/kernel/vm.cc
+++ b/kernel/vm.cc
@@ -23,7 +23,7 @@ enum { vm_debug = 0 };
 */

 vmnode::vmnode(u64 npg, vmntype ntype, inode *i, u64 off, u64 s)
-  : npages(npg), ref(0), type(ntype), ip(i), offset(off), sz(s)
+  : npages(npg), type(ntype), ip(i), offset(off), sz(s), ref_(0)
 {
  if (npg > NELEM(page))
    panic("vmnode too big\n");
@@ -44,12 +44,24 @@ vmnode::~vmnode()
 }

 void
-vmnode::decref()
+vmnode::decref(void)
 {
-  if(--ref == 0)
+  if(--ref_ == 0)
    delete this;
 }

+void
+vmnode::incref(void)
+{
+  ++ref_;
+}
+
+u64
+vmnode::ref(void)
+{
+  return ref_.load();
+}
+
 int
 vmnode::allocpg()
 {
@@ -126,7 +138,7 @@ vma::vma(vmap *vmap, uptr start, uptr end, enum vmatype vtype, vmnode *vmn) :
    vma_start(start), vma_end(end), va_type(vtype), n(vmn)
 {
  if (n)
-    n->ref++;
+    n->incref();
 }

 vma::~vma()
@@ -524,7 +536,7 @@ vmap::pagefault(uptr va, u32 err)
  u64 npg = (PGROUNDDOWN(va) - m->vma_start) / PGSIZE;
  if (vm_debug)
    cprintf("pagefault: err 0x%x va 0x%lx type %d ref %lu pid %d\n",
-            err, va, m->va_type, m->n->ref.load(), myproc()->pid);
+            err, va, m->va_type, m->n->ref(), myproc()->pid);

  if (m->n && !m->n->page[npg])
    if (m->n->allocpg() < 0)
@@ -553,7 +565,8 @@ vmap::pagefault(uptr va, u32 err)
  if (m->va_type == COW) {
    *pte = v2p(m->n->page[npg]) | PTE_P | PTE_U | PTE_COW;
  } else {
-    assert(m->n->ref == 1);
+    if (m->n->ref() != 1)
+      panic("vmap::pagefault: ref %lu va %lx", m->n->ref(), va);
    *pte = v2p(m->n->page[npg]) | PTE_P | PTE_U | PTE_W;
  }