Merge pull request #22317 from vespa-engine/havardpe/make-inspecting-config-generation-atomic

allow atomic inspection of current config generation

2 files changed, 8 insertions, 8 deletions

diff --git a/config/src/vespa/config/subscription/configsubscriptionset.cpp b/config/src/vespa/config/subscription/configsubscriptionset.cpp
index 1d5db778dda..48e2bdc2615 100644
--- a/config/src/vespa/config/subscription/configsubscriptionset.cpp
+++ b/config/src/vespa/config/subscription/configsubscriptionset.cpp
@@ -42,7 +42,7 @@ ConfigSubscriptionSet::acquireSnapshot(duration timeout, bool ignoreChange)
 
     steady_time now = steady_clock::now();
     const steady_time deadline = now + timeout;
-    int64_t lastGeneration = _currentGeneration;
+    int64_t lastGeneration = getGeneration();
     bool inSync = false;
 
     LOG(spam, "Going into nextConfig loop, time left is %f", vespalib::to_s(deadline - now));
@@ -55,7 +55,7 @@ ConfigSubscriptionSet::acquireSnapshot(duration timeout, bool ignoreChange)
         // Run nextUpdate on all subscribers to get them in sync.
         for (const auto & subscription : _subscriptionList) {
 
-            if (!subscription->nextUpdate(_currentGeneration, deadline) && !subscription->hasGenerationChanged()) {
+            if (!subscription->nextUpdate(getGeneration(), deadline) && !subscription->hasGenerationChanged()) {
                 subscription->reset();
                 continue;
             }
@@ -68,7 +68,7 @@ ConfigSubscriptionSet::acquireSnapshot(duration timeout, bool ignoreChange)
                 LOG(spam, "Config subscription did not change, id(%s), defname(%s)", key.getConfigId().c_str(), key.getDefName().c_str());
             }
             LOG(spam, "Previous generation is %" PRId64 ", updates is %" PRId64, lastGeneration, subscription->getGeneration());
-            if (isGenerationNewer(subscription->getGeneration(), _currentGeneration)) {
+            if (isGenerationNewer(subscription->getGeneration(), getGeneration())) {
                 numGenerationChanged++;
             }
             if (generation < 0) {
@@ -88,10 +88,10 @@ ConfigSubscriptionSet::acquireSnapshot(duration timeout, bool ignoreChange)
         }
     }
 
-    bool updated = inSync && isGenerationNewer(lastGeneration, _currentGeneration);
+    bool updated = inSync && isGenerationNewer(lastGeneration, getGeneration());
     if (updated) {
-        LOG(spam, "Config was updated from %" PRId64 " to %" PRId64, _currentGeneration, lastGeneration);
-        _currentGeneration = lastGeneration;
+        LOG(spam, "Config was updated from %" PRId64 " to %" PRId64, getGeneration(), lastGeneration);
+        _currentGeneration.store(lastGeneration, std::memory_order_relaxed);
         _state = CONFIGURED;
         for (const auto & subscription : _subscriptionList) {
             const ConfigKey & key(subscription->getKey());
diff --git a/config/src/vespa/config/subscription/configsubscriptionset.h b/config/src/vespa/config/subscription/configsubscriptionset.h
index 4b6d970770d..8daf7ae91ea 100644
--- a/config/src/vespa/config/subscription/configsubscriptionset.h
+++ b/config/src/vespa/config/subscription/configsubscriptionset.h
@@ -39,7 +39,7 @@ public:
      * @return generation number
      */
     int64_t getGeneration() const noexcept {
-        return _currentGeneration;
+        return _currentGeneration.load(std::memory_order_relaxed);
     }
 
     /**
@@ -69,7 +69,7 @@ private:
     const vespalib::duration        _maxNapTime;
     std::shared_ptr<IConfigContext> _context;             // Context to keep alive managers.
     IConfigManager &                _mgr;                 // The config manager that we use.
-    int64_t                         _currentGeneration;   // Holds the current config generation.
+    std::atomic<int64_t>            _currentGeneration;   // Holds the current config generation.
     SubscriptionList                _subscriptionList;    // List of current subscriptions.
     std::atomic<SubscriberState>    _state;               // Current state of this subscriber.
 };