make debug mode ~20% faster on linux

base/threading/platform_thread.h

 // Copyright (c) 2012 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.
 
 // WARNING: You should *NOT* be using this class directly.  PlatformThread is
 // the low-level platform-specific abstraction to the OS's threading interface.
 // You should instead be using a message-loop driven Thread, see thread.h.
 
 #ifndef BASE_THREADING_PLATFORM_THREAD_H_
 #define BASE_THREADING_PLATFORM_THREAD_H_
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(OS_POSIX)
 #include <pthread.h>
 #include <unistd.h>
 #endif
 
 namespace base {
 
+// Used for logging. Always an integer value.
 #if defined(OS_WIN)
 typedef DWORD PlatformThreadId;
 #elif defined(OS_POSIX)
 typedef pid_t PlatformThreadId;
 #endif
 
+// Used for thread checking and debugging.
+// Meant to be as fast as possible.

[Mark Mentovai, 2014/05/23 17:55:16]

Your comment should say something about the uniqueness guarantees: for example,
will the same thread always have the same PlatformThreadRef? Can two
PlatformThreadRefs identify the same thread? Can a PlatformThreadRef that once
referred to a now-dead thread subsequently refer to a different thread? It’s OK
for some of these to be unspecified, but you need to say more than what you’ve
said in this comment.

[hubbe, 2014/05/23 19:31:14]

Better?

+class PlatformThreadRef {
+ public:
+#if defined(OS_WIN)
+  typedef DWORD RefType;
+#elif defined(OS_POSIX)
+  typedef pthread_t RefType;
+#endif
+  PlatformThreadRef()
+      : id_(0) {
+  }
+
+  explicit PlatformThreadRef(RefType id)
+      : id_(id) {
+  }
+
+  bool operator==(PlatformThreadRef other) const {
+    return id_ == other.id_;
+  }
+
+  bool is_null() const {
+    return id_ == 0;
+  }
+ private:
+  RefType id_;
+};
+
+// Used to operate on threads.
 class PlatformThreadHandle {
  public:
 #if defined(OS_WIN)
   typedef void* Handle;
 #elif defined(OS_POSIX)
   typedef pthread_t Handle;
 #endif
 
   PlatformThreadHandle()
       : handle_(0),
@@ skipping 52 matching lines @@
    public:
     virtual void ThreadMain() = 0;
 
    protected:
     virtual ~Delegate() {}
   };
 
   // Gets the current thread id, which may be useful for logging purposes.
   static PlatformThreadId CurrentId();
 
+  // Gets the current thread reference, which can be used to check if
+  // we're on the right thread quickly.
+  static PlatformThreadRef CurrentRef();
+
   // Get the current handle.
   static PlatformThreadHandle CurrentHandle();
 
   // Yield the current thread so another thread can be scheduled.
   static void YieldCurrentThread();
 
   // Sleeps for the specified duration.
   static void Sleep(base::TimeDelta duration);
 
   // Sets the thread name visible to debuggers/tools. This has no effect
@@ skipping 37 matching lines @@
   static void SetThreadPriority(PlatformThreadHandle handle,
                                 ThreadPriority priority);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_PLATFORM_THREAD_H_