Do not abort when a shutdown thread joins itself (#37)

std::thread::join throws system_error if the caller is the thread being
joined. That uncaught exception aborted the process during shutdown.
Detach the current thread instead, and catch a join that still throws.

5 files changed, 63 insertions, 4 deletions

diff --git a/indra/llcommon/llthread.h b/indra/llcommon/llthread.h
index b97d479abc..38a5f4669f 100644
--- a/indra/llcommon/llthread.h
+++ b/indra/llcommon/llthread.h
@@ -33,6 +33,32 @@
 
 extern void set_thread_name(const char* threadName);
 
+// Join unless this is the calling thread. Joining the current thread throws
+// system_error(resource_deadlock_would_occur) and aborts via std::terminate.
+inline void ll_join_thread(std::thread& thread)
+{
+    if (!thread.joinable())
+    {
+        return;
+    }
+    if (thread.get_id() == std::this_thread::get_id())
+    {
+        thread.detach();
+        return;
+    }
+    try
+    {
+        thread.join();
+    }
+    catch (const std::system_error&)
+    {
+        if (thread.joinable())
+        {
+            thread.detach();
+        }
+    }
+}
+
 namespace LLTrace
 {
     class ThreadRecorder;
diff --git a/indra/llcommon/threadpool.cpp b/indra/llcommon/threadpool.cpp
index 6adbdffba8..668c8ba598 100644
--- a/indra/llcommon/threadpool.cpp
+++ b/indra/llcommon/threadpool.cpp
@@ -20,6 +20,7 @@
 #include "commoncontrol.h"
 #include "llerror.h"
 #include "llevents.h"
+#include "llthread.h"
 #include "llsd.h"
 #include "stringize.h"
 
@@ -127,8 +128,17 @@ void LL::ThreadPoolBase::close()
         {
             if (pair.second.joinable())
             {
+                // close() runs on a worker when the LLApp status listener
+                // fires on that thread. Joining it throws and aborts shutdown.
+                if (pair.second.get_id() == std::this_thread::get_id())
+                {
+                    LL_WARNS("ThreadPool") << mName << " detaching current thread "
+                        << pair.first << LL_ENDL;
+                    pair.second.detach();
+                    continue;
+                }
                 LL_DEBUGS("ThreadPool") << mName << " waiting on thread " << pair.first << LL_ENDL;
-                pair.second.join();
+                ll_join_thread(pair.second);
             }
         }
         LL_DEBUGS("ThreadPool") << mName << " shutdown complete" << LL_ENDL;
diff --git a/indra/llcorehttp/llwebsocketmgr.cpp b/indra/llcorehttp/llwebsocketmgr.cpp
index ef07295eed..701fbd5446 100644
--- a/indra/llcorehttp/llwebsocketmgr.cpp
+++ b/indra/llcorehttp/llwebsocketmgr.cpp
@@ -28,6 +28,7 @@
 
 #include "llwebsocketmgr.h"
 #include "llerror.h"
+#include "llthread.h"
 #include "llsdserialize.h"
 #include "llhost.h"
 #include "llsdjson.h"
@@ -508,7 +509,7 @@ void LLWebsocketMgr::WSServer::stop()
                 << "thread-boundary regression." << LL_ENDL;
         }
 
-        mServerThread.join();
+        ll_join_thread(mServerThread);
         LL_INFOS("WebSocket") << "WebSocket server thread joined for: " << mServerName << LL_ENDL;
     }
     onStopped();
diff --git a/indra/llwebrtc/llwebrtc.cpp b/indra/llwebrtc/llwebrtc.cpp
index d07f801051..ff68437cf3 100644
--- a/indra/llwebrtc/llwebrtc.cpp
+++ b/indra/llwebrtc/llwebrtc.cpp
@@ -29,6 +29,7 @@
 #include <chrono>
 #include <future>
 #include <thread>
+#include <system_error>
 #include <string.h>
 #include "api/audio/create_audio_device_module.h"
 #include "api/audio_codecs/audio_decoder_factory.h"
@@ -558,7 +559,27 @@ bool LLWebRTCImpl::terminate()
         return false;
     }
 
-    shutdown_thread.join();
+    // Joining the current thread throws system_error and aborts the process.
+    if (shutdown_thread.get_id() == std::this_thread::get_id())
+    {
+        RTC_LOG(LS_WARNING) << __FUNCTION__ << ": shutdown thread is the caller; detaching.";
+        shutdown_thread.detach();
+    }
+    else
+    {
+        try
+        {
+            shutdown_thread.join();
+        }
+        catch (const std::system_error& e)
+        {
+            RTC_LOG(LS_WARNING) << __FUNCTION__ << ": join failed: " << e.what();
+            if (shutdown_thread.joinable())
+            {
+                shutdown_thread.detach();
+            }
+        }
+    }
 
     webrtc::LogMessage::RemoveLogToStream(mLogSink);
     return true;
diff --git a/indra/newview/llinventorymodel.cpp b/indra/newview/llinventorymodel.cpp
index b818a66b30..31fd699335 100644
--- a/indra/newview/llinventorymodel.cpp
+++ b/indra/newview/llinventorymodel.cpp
@@ -31,6 +31,7 @@
 #include <thread>
 
 #include "llinventorymodel.h"
+#include "llthread.h"
 
 #include "llaisapi.h"
 #include "llagent.h"
@@ -2505,7 +2506,7 @@ void LLInventoryModel::waitForPendingCacheWrites()
     {
         if (thread.joinable())
         {
-            thread.join();
+            ll_join_thread(thread);
         }
     }
     sPendingCacheThreads.clear();