From: José Fonseca <jose.r.fonseca@gmail.com>
Date: Thu, 22 Dec 2011 22:19:40 +0000 (+0000)
Subject: Use thread local storage to specify unique and low integer thread ids.
X-Git-Url: https://git.cworth.org/git?a=commitdiff_plain;h=5926761f1682c26266a78f2674e58beff3bfae88;p=apitrace

Use thread local storage to specify unique and low integer thread ids.
---

diff --git a/common/os_thread.hpp b/common/os_thread.hpp
index 727ad6a..7349255 100644
--- a/common/os_thread.hpp
+++ b/common/os_thread.hpp
@@ -41,38 +41,69 @@
 namespace os {
 
 
-    namespace thread {
-
-        /**
-         * Thread ID
-         *
-         * XXX: Actually C++11 thread::id is not an integral type, but we rely on that.
-         */
+    template <typename T>
+    class thread_specific_ptr
+    {
+    private:
 #ifdef _WIN32
-        typedef DWORD id;
+        DWORD dwTlsIndex;
 #else
-        typedef pthread_t id;
-#endif
+        pthread_key_t key;
 
-    } /* namespace thread */
+        static void destructor(void *ptr) {
+            delete static_cast<T *>(ptr);
+        }
+#endif
 
+    public:
+        thread_specific_ptr(void) {
+#ifdef _WIN32
+            dwTlsIndex = TlsAlloc();
+#else
+            pthread_key_create(&key, &destructor);
+#endif
+        }
 
-    namespace this_thread {
+        ~thread_specific_ptr() {
+#ifdef _WIN32
+            TlsFree(dwTlsIndex);
+#else
+            pthread_key_delete(key);
+#endif
+        }
 
-        /**
-         * Get current thread ID.
-         */
-        inline thread::id
-        get_id(void) {
+        T* get(void) const {
+            void *ptr;
 #ifdef _WIN32
-            return GetCurrentThreadId();
+            ptr = TlsGetValue(dwTlsIndex);
 #else
-            return pthread_self();
+            ptr = pthread_getspecific(key);
 #endif
+            return static_cast<T*>(ptr);
         }
 
-    } /* namespace this_thread */
+        T* operator -> (void) const
+        {
+            return get();
+        }
+
+        T& operator * (void) const
+        {
+            return *get();
+        }
 
+        void reset(T* new_value=0) {
+            T * old_value = get();
+#ifdef _WIN32
+            TlsSetValue(dwTlsIndex, new_value);
+#else
+            pthread_setspecific(key, new_value);
+#endif
+            if (old_value) {
+                delete old_value;
+            }
+        }
+    };
 
 } /* namespace os */
 
diff --git a/common/trace_writer_local.cpp b/common/trace_writer_local.cpp
index bb06d90..77c8bd6 100644
--- a/common/trace_writer_local.cpp
+++ b/common/trace_writer_local.cpp
@@ -124,6 +124,9 @@ LocalWriter::open(void) {
 #endif
 }
 
+static unsigned next_thread_id = 0;
+static os::thread_specific_ptr<unsigned> thread_id_specific_ptr;
+
 unsigned LocalWriter::beginEnter(const FunctionSig *sig) {
     os::acquireMutex();
     ++acquired;
@@ -132,9 +135,18 @@ unsigned LocalWriter::beginEnter(const FunctionSig *sig) {
         open();
     }
 
-    os::thread::id id = os::this_thread::get_id();
+    unsigned *thread_id_ptr = thread_id_specific_ptr.get();
+    unsigned thread_id;
+    if (thread_id_ptr) {
+        thread_id = *thread_id_ptr;
+    } else {
+        thread_id = next_thread_id++;
+        thread_id_ptr = new unsigned;
+        *thread_id_ptr = thread_id;
+        thread_id_specific_ptr.reset(thread_id_ptr);
+    }
 
-    return Writer::beginEnter(sig, static_cast<unsigned>(id));
+    return Writer::beginEnter(sig, thread_id);
 }
 
 void LocalWriter::endEnter(void) {