DRTVWR-476: Make llcoro::logname() distinguish different threads.

Actually, introduce static LLCoros::logname() and make the namespaced free
function an alias for that.

Because CoroData is a subclass of LLInstanceTracker with a key, every instance
requires a distinct key. That conflicts with our "getName() returns empty
string for default coroutine on thread" convention. Introduce a new CoroData
constructor, specifically for the default coroutine on each thread, that
initializes the getName() name to empty string while providing a distinct
"mainN" key. Make get_CoroData() use that new constructor for its thread_local
instance, passing an atomic<int> incremented each time we initialize one for a
new thread.

Then LLCoros::logname() returns either the getName() name or the key.

2 files changed, 33 insertions, 10 deletions

diff --git a/indra/llcommon/llcoros.cpp b/indra/llcommon/llcoros.cpp
index 9e0cceda2b..adb86c4e0b 100644
--- a/indra/llcommon/llcoros.cpp
+++ b/indra/llcommon/llcoros.cpp
@@ -34,6 +34,7 @@
 #include "llcoros.h"
 // STL headers
 // std headers
+#include <atomic>
 // external library headers
 #include <boost/bind.hpp>
 #include <boost/fiber/fiber.hpp>
@@ -73,10 +74,9 @@ LLCoros::CoroData& LLCoros::get_CoroData(const std::string& caller)
     // canonical values.
     if (! current)
     {
-        // It's tempting to provide a distinct name for each thread's "main
-        // coroutine." But as getName() has always returned the empty string
-        // to mean "not in a coroutine," empty string should suffice here.
-        static thread_local CoroData sMain("");
+        static std::atomic<int> which_thread(0);
+        // Use alternate CoroData constructor.
+        static thread_local CoroData sMain(which_thread++);
         // We need not reset() the local_ptr to this instance; we'll simply
         // find it again every time we discover that current is null.
         current = &sMain;
@@ -198,6 +198,13 @@ std::string LLCoros::getName()
     return get_CoroData("getName()").mName;
 }
 
+//static
+std::string LLCoros::logname()
+{
+    LLCoros::CoroData& data(get_CoroData("logname()"));
+    return data.mName.empty()? data.getKey() : data.mName;
+}
+
 void LLCoros::setStackSize(S32 stacksize)
 {
     LL_DEBUGS("LLCoros") << "Setting coroutine stack size to " << stacksize << LL_ENDL;
@@ -353,3 +360,16 @@ LLCoros::CoroData::CoroData(const std::string& name):
     mCreationTime(LLTimer::getTotalSeconds())
 {
 }
+
+LLCoros::CoroData::CoroData(int n):
+    // This constructor is used for the thread_local instance belonging to the
+    // default coroutine on each thread. We must give each one a different
+    // LLInstanceTracker key because LLInstanceTracker's map spans all
+    // threads, but we want the default coroutine on each thread to have the
+    // empty string as its visible name because some consumers test for that.
+    LLInstanceTracker<CoroData, std::string>("main" + stringize(n)),
+    mName(),
+    mConsuming(false),
+    mCreationTime(LLTimer::getTotalSeconds())
+{
+}
diff --git a/indra/llcommon/llcoros.h b/indra/llcommon/llcoros.h
index 2e4cd8ccad..95859198d4 100644
--- a/indra/llcommon/llcoros.h
+++ b/indra/llcommon/llcoros.h
@@ -143,6 +143,13 @@ public:
     static std::string getName();
 
     /**
+     * This variation returns a name suitable for log messages: the explicit
+     * name for an explicitly-launched coroutine, or "mainN" for the default
+     * coroutine on a thread.
+     */
+    static std::string logname();
+
+    /**
      * For delayed initialization. To be clear, this will only affect
      * coroutines launched @em after this point. The underlying facility
      * provides no way to alter the stack size of any running coroutine.
@@ -272,6 +279,7 @@ private:
     struct CoroData: public LLInstanceTracker<CoroData, std::string>
     {
         CoroData(const std::string& name);
+        CoroData(int n);
 
         // tweaked name of the current coroutine
         const std::string mName;
@@ -292,12 +300,7 @@ namespace llcoro
 {
 
 inline
-std::string logname()
-{
-    static std::string main("main");
-    std::string name(LLCoros::getName());
-    return name.empty()? main : name;
-}
+std::string logname() { return LLCoros::logname(); }
 
 } // llcoro