Bugfix in process handle: Do detaching from owner process separately from derefing.

src/vm/process_handle.h

 // Copyright (c) 2015, the Fletch project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 #ifndef SRC_VM_PROCESS_HANDLE_H_
 #define SRC_VM_PROCESS_HANDLE_H_
 
 #include "src/shared/platform.h"
 
 #include "src/vm/spinlock.h"
 #include "src/vm/refcounted.h"
 
 namespace fletch {
 
 class Process;
 
 class ProcessHandle : public Refcounted<ProcessHandle> {
  public:
   explicit ProcessHandle(Process* process) : process_(process) {}
 
   Spinlock* lock() { return &spinlock_; }
 
   Process* process() const { return process_; }
 
  private:
   friend class Process;
 
-  static void OwnerProcessTerminating(ProcessHandle* handle) {
-    handle->lock()->Lock();
-    ASSERT(handle->process_ != NULL);
-    handle->process_ = NULL;
-    if (!handle->DecrementRefWithoutDelete()) {
-      handle->lock()->Unlock();

[kustermann, 2015/10/29 11:17:20]

The DecrementRefWithoutDelete() & Unlock/Delete is atomic and therefore racing
with normal DecrementRef().

(I've adopted that model from Port - which takes a spinlock on every deref -
which I avoid in [Refcounted].)

-    } else {
-      delete handle;
-    }
+  void OwnerProcessTerminating() {
+    ScopedSpinlock locker(&spinlock_);
+    ASSERT(process_ != NULL);
+    process_ = NULL;
   }
 
   Process* process_;
   Spinlock spinlock_;
 };
 
 }  // namespace fletch
 
 #endif  // SRC_VM_PROCESS_HANDLE_H_