[C++] Use TLS for Stats again

3 files changed, 18 insertions, 6 deletions

diff --git a/stats.cc b/stats.cc
index 920d13f..7afda4c 100644
--- a/stats.cc
+++ b/stats.cc
@@ -22,12 +22,14 @@
 #include "log.h"
 #include "mutex.h"
 #include "stringprintf.h"
+#include "thread_local.h"
 #include "timeutil.h"
 
 namespace {
 
 mutex g_mu;
 vector<Stats*>* g_stats;
+DEFINE_THREAD_LOCAL(double, g_start_time);
 
 }  // namespace
 
@@ -45,17 +47,17 @@ string Stats::String() const {
 }
 
 void Stats::Start() {
-  CHECK(!start_time_);
+  CHECK(!TLS_REF(g_start_time));
+  TLS_REF(g_start_time) = GetTime();
   unique_lock<mutex> lock(mu_);
-  start_time_ = GetTime();
   cnt_++;
 }
 
 double Stats::End() {
+  CHECK(TLS_REF(g_start_time));
+  double e = GetTime() - TLS_REF(g_start_time);
+  TLS_REF(g_start_time) = 0;
   unique_lock<mutex> lock(mu_);
-  CHECK(start_time_);
-  double e = GetTime() - start_time_;
-  start_time_ = 0;
   elapsed_ += e;
   return e;
 }
diff --git a/stats.h b/stats.h
index 8d3a41b..6244b54 100644
--- a/stats.h
+++ b/stats.h
@@ -34,7 +34,6 @@ class Stats {
   friend class ScopedStatsRecorder;
 
   const char* name_;
-  double start_time_;
   double elapsed_;
   int cnt_;
   mutable mutex mu_;
diff --git a/thread_local.h b/thread_local.h
index 3bbf663..28b146a 100644
--- a/thread_local.h
+++ b/thread_local.h
@@ -39,6 +39,13 @@
 
 #include "log.h"
 
+#ifdef __linux__
+
+#define DEFINE_THREAD_LOCAL(Type, name) thread_local Type name
+#define TLS_REF(x) x
+
+#else
+
 // Thread local storage implementation which uses pthread.
 // Note that DEFINE_THREAD_LOCAL creates a global variable just like
 // thread local storage based on __thread keyword. So we should not use
@@ -88,4 +95,8 @@ class ThreadLocal {
   }                                                     \
   ThreadLocal<Type, &name##_key, &name##_once> name;
 
+#define TLS_REF(x) x.Ref()
+
+#endif
+
 #endif  // THREAD_LOCAL_H_