Merge pull request #21273 from vespa-engine/vekterli/make-fnet-io-components-count-atomic

Make FNET_TransportThread IO components counter atomic

2 files changed, 10 insertions, 6 deletions

diff --git a/fnet/src/vespa/fnet/transport_thread.cpp b/fnet/src/vespa/fnet/transport_thread.cpp
index 8a0f3a8534a..53f8fea40cd 100644
--- a/fnet/src/vespa/fnet/transport_thread.cpp
+++ b/fnet/src/vespa/fnet/transport_thread.cpp
@@ -9,6 +9,7 @@
 #include "transport.h"
 #include <vespa/vespalib/net/socket_spec.h>
 #include <vespa/vespalib/net/server_socket.h>
+#include <vespa/vespalib/util/atomic.h>
 #include <vespa/vespalib/util/gate.h>
 #include <csignal>
 
@@ -19,6 +20,7 @@ using vespalib::ServerSocket;
 using vespalib::SocketHandle;
 using vespalib::SocketSpec;
 using vespalib::steady_clock;
+using namespace vespalib::atomic;
 
 namespace {
 
@@ -46,7 +48,7 @@ FNET_TransportThread::AddComponent(FNET_IOComponent *comp)
         _componentsTail = comp;
         if (_timeOutHead == nullptr)
             _timeOutHead = comp;
-        _componentCnt++;
+        store_relaxed(_componentCnt, load_relaxed(_componentCnt) + 1);
     } else {
         comp->_ioc_prev = nullptr;
         comp->_ioc_next = _componentsHead;
@@ -56,7 +58,7 @@ FNET_TransportThread::AddComponent(FNET_IOComponent *comp)
             _componentsHead->_ioc_prev = comp;
         }
         _componentsHead = comp;
-        _componentCnt++;
+        store_relaxed(_componentCnt, load_relaxed(_componentCnt) + 1);
     }
 }
 
@@ -74,7 +76,7 @@ FNET_TransportThread::RemoveComponent(FNET_IOComponent *comp)
         comp->_ioc_prev->_ioc_next = comp->_ioc_next;
     if (comp->_ioc_next != nullptr)
         comp->_ioc_next->_ioc_prev = comp->_ioc_prev;
-    _componentCnt--;
+    store_relaxed(_componentCnt, load_relaxed(_componentCnt) - 1);
 }
 
 
@@ -549,7 +551,7 @@ FNET_TransportThread::endEventLoop() {
     assert(_componentsHead == nullptr &&
            _componentsTail == nullptr &&
            _timeOutHead    == nullptr &&
-           _componentCnt   == 0    &&
+           load_relaxed(_componentCnt) == 0 &&
            _queue.IsEmpty_NoLock() &&
            _myQueue.IsEmpty_NoLock());
 
diff --git a/fnet/src/vespa/fnet/transport_thread.h b/fnet/src/vespa/fnet/transport_thread.h
index 4452eba2825..cf1f68a8b39 100644
--- a/fnet/src/vespa/fnet/transport_thread.h
+++ b/fnet/src/vespa/fnet/transport_thread.h
@@ -39,7 +39,7 @@ private:
     FNET_IOComponent        *_componentsHead; // I/O component list head
     FNET_IOComponent        *_timeOutHead;    // first IOC in list to time out
     FNET_IOComponent        *_componentsTail; // I/O component list tail
-    uint32_t                 _componentCnt;   // # of components
+    std::atomic<uint32_t>    _componentCnt;   // # of components
     FNET_IOComponent        *_deleteList;     // IOC delete list
     Selector                 _selector;       // I/O event generator
     FNET_PacketQueue_NoLock  _queue;          // outer event queue
@@ -266,7 +266,9 @@ public:
      *
      * @return the current number of IOComponents.
      **/
-    uint32_t GetNumIOComponents() { return _componentCnt; }
+    uint32_t GetNumIOComponents() const noexcept {
+        return _componentCnt.load(std::memory_order_relaxed);
+    }
 
     /**
      * Add an I/O component to the working set of this transport