some more out-of-memory handling

2b285c52 · Nickolai Zeldovich · ba71a527 · 2b285c52 · 2b285c52 · 2b285c52
--- a/include/cpputil.hh
+++ b/include/cpputil.hh
@@ -152,3 +152,26 @@ extern void *__dso_handle;
    kmfree(p, sizeof(classname));                                   \
  }

+template<class T>
+class scoped_cleanup_obj {
+ private:
+  T handler_;
+  bool active_;
+
+ public:
+  scoped_cleanup_obj(const T& h) : handler_(h), active_(true) {};
+  ~scoped_cleanup_obj() { if (active_) handler_(); }
+  void dismiss() { active_ = false; }
+
+  void operator=(const scoped_cleanup_obj&) = delete;
+  scoped_cleanup_obj(const scoped_cleanup_obj&) = delete;
+  scoped_cleanup_obj(scoped_cleanup_obj&& other) :
+    handler_(other.handler_), active_(other.active_) { other.dismiss(); }
+};
+
+template<class T>
+scoped_cleanup_obj<T>
+scoped_cleanup(const T& h)
+{
+  return scoped_cleanup_obj<T>(h);
+}
--- a/include/filetable.hh
+++ b/include/filetable.hh
@@ -8,8 +8,6 @@ public:

  filetable* copy() {
    filetable* t = alloc();
-    if (t == nullptr)
-      return nullptr;

    for(int fd = 0; fd < NOFILE; fd++) {
      sref<file> f;

--- a/kernel/proc.cc
+++ b/kernel/proc.cc
@@ -354,19 +354,18 @@ fork(int flags)
  if((np = proc::alloc()) == 0)
    throw std::bad_alloc();

-  // XXX use a scoped cleanup handler to do xnspid->remove & freeproc
+  auto proc_cleanup = scoped_cleanup([&np]() {
+      if (!xnspid->remove(np->pid, &np))
+        panic("fork: ns_remove");
+      freeproc(np);
+    });

  if(flags & FORK_SHARE_VMAP) {
    np->vmap = myproc()->vmap;
    np->vmap->ref++;
  } else {
    // Copy process state from p.
-    if((np->vmap = myproc()->vmap->copy(cow)) == 0){
-      if (!xnspid->remove(np->pid, &np))
-	panic("fork: ns_remove");
-      freeproc(np);
-      throw std::bad_alloc();
-    }
+    np->vmap = myproc()->vmap->copy(cow);
  }

  np->parent = myproc();
@@ -383,11 +382,6 @@ fork(int flags)
    np->ftable = myproc()->ftable;
  } else {
    np->ftable = myproc()->ftable->copy();
-    if (np->ftable == nullptr) {
-      // XXX(sbw) leaking?
-      freeproc(np);
-      throw std::bad_alloc();
-    }
  }

  np->cwd = idup(myproc()->cwd);
@@ -402,6 +396,7 @@ fork(int flags)
  addrun(np);
  release(&np->lock);

+  proc_cleanup.dismiss();
  return pid;
 }

@@ -412,8 +407,6 @@ finishproc(struct proc *p)
    p->vmap->decref();
  if (p->uwq != nullptr)
    p->uwq->dec();
-  ksfree(slab_stack, p->kstack);
-  p->kstack = 0;
  p->pid = 0;
  p->parent = 0;
  p->name[0] = 0;