From 209adc1be4f17d95850f8a6c4ca9d1dc38103817 Mon Sep 17 00:00:00 2001
From: Tor Brede Vekterli <vekterli@oath.com>
Date: Thu, 10 Jan 2019 14:45:41 +0000
Subject: Use relaxed atomics for FNET_TransportThread shutdown flag

---
 fnet/src/vespa/fnet/transport_thread.cpp | 10 +++++-----
 fnet/src/vespa/fnet/transport_thread.h   |  7 ++++++-
 2 files changed, 11 insertions(+), 6 deletions(-)

(limited to 'fnet')

diff --git a/fnet/src/vespa/fnet/transport_thread.cpp b/fnet/src/vespa/fnet/transport_thread.cpp
index b38e2f0aa08..8ee33ad7960 100644
--- a/fnet/src/vespa/fnet/transport_thread.cpp
+++ b/fnet/src/vespa/fnet/transport_thread.cpp
@@ -116,7 +116,7 @@ FNET_TransportThread::PostEvent(FNET_ControlPacket *cpacket,
     bool wasEmpty;
     {
         std::unique_lock<std::mutex> guard(_lock);
-        if (_shutdown) {
+        if (IsShutDown()) {
             guard.unlock();
             SafeDiscardEvent(cpacket, context);
             return false;
@@ -381,8 +381,8 @@ FNET_TransportThread::ShutDown(bool waitFinished)
     bool wasEmpty = false;
     {
         std::lock_guard<std::mutex> guard(_lock);
-        if (!_shutdown) {
-            _shutdown = true;
+        if (!IsShutDown()) {
+            _shutdown.store(true, std::memory_order_relaxed);
             wasEmpty  = _queue.IsEmpty_NoLock();
         }
     }
@@ -519,7 +519,7 @@ FNET_TransportThread::EventLoopIteration()
     FastOS_Time beforeGetEvents;
 #endif
 
-    if (!_shutdown) {
+    if (!IsShutDown()) {
 
 #ifdef FNET_SANITY_CHECKS
         // Warn if event loop takes more than 250ms
@@ -569,7 +569,7 @@ FNET_TransportThread::EventLoopIteration()
         FlushDeleteList();
     }                      // -- END OF MAIN EVENT LOOP --
 
-    if (!_shutdown)
+    if (!IsShutDown())
         return true;
     if (_finished)
         return false;
diff --git a/fnet/src/vespa/fnet/transport_thread.h b/fnet/src/vespa/fnet/transport_thread.h
index 86c7cf1dfcd..ffbbb7acc0f 100644
--- a/fnet/src/vespa/fnet/transport_thread.h
+++ b/fnet/src/vespa/fnet/transport_thread.h
@@ -10,6 +10,7 @@
 #include <vespa/fastos/time.h>
 #include <vespa/vespalib/net/socket_handle.h>
 #include <vespa/vespalib/net/selector.h>
+#include <atomic>
 #include <mutex>
 #include <condition_variable>
 
@@ -48,7 +49,7 @@ private:
     std::condition_variable  _cond;           // used for synchronization
     std::recursive_mutex     _pseudo_thread;  // used after transport thread has shut down
     bool                     _started;        // event loop started ?
-    bool                     _shutdown;       // should stop event loop ?
+    std::atomic<bool>        _shutdown;       // should stop event loop ?
     bool                     _finished;       // event loop stopped ?
     bool                     _waitFinished;   // someone is waiting for _finished
     bool                     _deleted;        // destructor called ?
@@ -171,6 +172,10 @@ private:
      **/
     bool EventLoopIteration();
 
+    bool IsShutDown() const noexcept {
+        return _shutdown.load(std::memory_order_relaxed);
+    }
+
 public:
     /**
      * Construct a transport object. To activate your newly created
-- 
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