Make much of the proxy thread-safe with 1 great big lock.

ppapi/shared_impl/proxy_lock.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PPAPI_SHARED_IMPL_PROXY_LOCK_H_
+#define PPAPI_SHARED_IMPL_PROXY_LOCK_H_
+
+#include "base/basictypes.h"
+
+namespace base {
+class Lock;
+}
+
+namespace ppapi {
+
+// This is the one lock to rule them all for the ppapi proxy. All PPB interface
+// functions that need to be synchronized should lock this lock on entry. This
+// is normally accomplished by using an appropriate Enter RAII object at the
+// beginning of each thunk function.
+//
+// TODO(dmichael): If this turns out to be too slow and contentious, we'll want
+// to use multiple locks. E.g., one for the var tracker, one for the resource
+// tracker, etc.
+class ProxyLock {
+ public:
+  // Acquire the proxy lock. If it is currently held by another thread, block
+  // until it is available. If the lock has not been set using the 'Set' method,
+  // this operation does nothing. That is the normal case for the host side;
+  // see PluginResourceTracker for where the lock gets set for the out-of-
+  // process plugin case.
+  static void Acquire();
+  // Relinquish the proxy lock. If the lock has not been set, this does nothing.
+  static void Release();
+
+  // Set the lock that ProxyLock will use. The caller is responsible for
+  // ensuring that the lock stays valid so long as the ProxyLock may be in use.
+  static void Set(base::Lock* lock);
+  // Set the lock to NULL.
+  static void Reset();
+ private:
+  static base::Lock* lock_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ProxyLock);
+};
+
+// A simple RAII class for locking the PPAPI proxy lock on entry and releasing
+// on exit. This is for simple interfaces that don't use the 'thunk' system,
+// such as PPB_Var and PPB_Core.
+class ProxyAutoLock {
+ public:
+  ProxyAutoLock() {
+    ProxyLock::Acquire();
+  }
+  ~ProxyAutoLock() {
+    ProxyLock::Release();
+  }
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ProxyAutoLock);
+};
+
+// The inverse of the above; unlock on construction, lock on destruction. This
+// is useful for calling out to the plugin, when we need to unlock but ensure
+// that we re-acquire the lock when the plugin is returns or raises an
+// exception.
+class ProxyAutoUnlock {
+ public:
+  ProxyAutoUnlock() {
+    ProxyLock::Release();
+  }
+  ~ProxyAutoUnlock() {
+    ProxyLock::Acquire();
+  }
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ProxyAutoUnlock);
+};
+
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_PROXY_LOCK_H_