make debug mode ~20% faster on linux

base/threading/platform_thread_posix.cc

 // 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.
 
 #include "base/threading/platform_thread.h"
 
 #include <errno.h>
 #include <sched.h>
 
 #include "base/lazy_instance.h"
@@ skipping 131 matching lines @@
 
 }  // namespace
 
 // static
 PlatformThreadId PlatformThread::CurrentId() {
   // Pthreads doesn't have the concept of a thread ID, so we have to reach down
   // into the kernel.
 #if defined(OS_MACOSX)
   return pthread_mach_thread_np(pthread_self());
 #elif defined(OS_LINUX)
-  return syscall(__NR_gettid);
+  return pthread_self();

[piman, 2014/05/20 05:09:22]

On my system, PlatformThreadId (a pid_t currently) is an int, whereas pthread_t
is an unsigned long int.

Can we change the definition of PlatformThreadId into a pthread_t on OS_LINUX?

 #elif defined(OS_ANDROID)
   return gettid();
 #elif defined(OS_SOLARIS) || defined(OS_QNX)
   return pthread_self();
 #elif defined(OS_NACL) && defined(__GLIBC__)
   return pthread_self();
 #elif defined(OS_NACL) && !defined(__GLIBC__)
   // Pointers are 32-bits in NaCl.
   return reinterpret_cast<int32>(pthread_self());
 #elif defined(OS_POSIX)
@@ skipping 61 matching lines @@
 // static
 void PlatformThread::Join(PlatformThreadHandle thread_handle) {
   // Joining another thread may block the current thread for a long time, since
   // the thread referred to by |thread_handle| may still be running long-lived /
   // blocking tasks.
   base::ThreadRestrictions::AssertIOAllowed();
   CHECK_EQ(0, pthread_join(thread_handle.handle_, NULL));
 }
 
 }  // namespace base