trace_event support for thread names

base/debug/trace_event.cc

Index: base/debug/trace_event.cc
diff --git a/base/debug/trace_event.cc b/base/debug/trace_event.cc
index d467055be9646f6aea8216eaf80f89a0b68a48e4..b0cdb76cb4a539b4a0a12aaef62d9d66096850a6 100644
--- a/base/debug/trace_event.cc
+++ b/base/debug/trace_event.cc
@@ -104,6 +104,8 @@ const char* GetPhaseStr(TraceEventPhase phase) {
       return "I";
     case TRACE_EVENT_PHASE_END:
       return "E";
+    case TRACE_EVENT_PHASE_METADATA:
+      return "M";
     default:
       NOTREACHED() << "Invalid phase argument";
       return "?";
@@ -295,8 +297,10 @@ void TraceLog::SetEnabled(bool enabled) {
       g_categories[i].enabled = enabled;
     }
   } // release lock
-  if (!enabled)
+  if (!enabled) {
+    AddCurrentMetadataEvents();
     Flush();
+  }
 }
 
 float TraceLog::GetBufferPercentFull() const {
@@ -361,6 +365,14 @@ int TraceLog::AddTraceEvent(TraceEventPhase phase,
       return -1;
     if (logged_events_.size() >= kTraceEventBufferSize)
       return -1;
+    PlatformThreadId thread_id = PlatformThread::CurrentId();
+    if (thread_names_.find(thread_id) == thread_names_.end()) {

[Sigurður Ásgeirsson, 2011/08/04 12:31:39]

On Windows, thread and process IDs are reused quite aggressively, so this may
end up not recording the thread name for a thread that's inherited a previously
used thread ID.
You can either (simply) set this on every event, or else you could maintain a
thread-local boolean variable "did_record_name".

[nduca, 2011/08/04 18:17:38]

Thats an awesome idea.

+      const char* name = PlatformThread::GetName();
+      // Store something even for unnamed threads so we don't keep searching the
+      // thread_names_ map every time.
+      thread_names_[thread_id] = name ? name : "";
+    }
+
     if (threshold_begin_id > -1) {
       DCHECK(phase == base::debug::TRACE_EVENT_PHASE_END);
       size_t begin_i = static_cast<size_t>(threshold_begin_id);
@@ -380,7 +392,7 @@ int TraceLog::AddTraceEvent(TraceEventPhase phase,
     ret_begin_id = static_cast<int>(logged_events_.size());
     logged_events_.push_back(
         TraceEvent(static_cast<unsigned long>(base::GetCurrentProcId()),
-                   PlatformThread::CurrentId(),
+                   thread_id,
                    now, phase, category, name,
                    arg1_name, arg1_val,
                    arg2_name, arg2_val,
@@ -419,6 +431,25 @@ void TraceLog::AddTraceEventEtw(TraceEventPhase phase,
   }
 }
 
+void TraceLog::AddCurrentMetadataEvents() {
+  static const TraceCategory* metadata_category =
+      GetCategoryInternal("__metadata");
+  for(base::hash_map<PlatformThreadId, std::string>::iterator it =

[Sigurður Ásgeirsson, 2011/08/04 12:31:39]

lock_.AssertHeld().
However, I don't think you're holding the lock here, so you have a race on the
map?

[nduca, 2011/08/04 18:17:38]

Nice catch!

+          thread_names_.begin();
+      it != thread_names_.end();
+      it++) {
+    if (!it->second.empty())
+      logged_events_.push_back(
+          TraceEvent(static_cast<unsigned long>(base::GetCurrentProcId()),
+                     it->first,
+                     TimeTicks(), base::debug::TRACE_EVENT_PHASE_METADATA,
+                     metadata_category, "thread_name",
+                     "name", it->second.c_str(),
+                     NULL, 0,
+                     false));
+  }
+}
+
 void TraceLog::Resurrect() {
   StaticMemorySingletonTraits<TraceLog>::Resurrect();
 }