minor improvements for the thread safe observer pattern (#1808)

lballabio · Oct 20, 2023 · e5bef2e · e5bef2e
2 parents 3a9fd60 + c7a3104
commit e5bef2e
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Showing 2 changed files with 25 additions and 14 deletions.
diff --git a/ql/patterns/observable.cpp b/ql/patterns/observable.cpp
@@ -161,9 +161,8 @@ namespace QuantLib {
 
         if (ObservableSettings::instance().updatesDeferred()) {
             std::lock_guard<std::mutex> sLock(ObservableSettings::instance().mutex_);
-            if (ObservableSettings::instance().updatesDeferred()) {
+            if (ObservableSettings::instance().updatesDeferred())
                 ObservableSettings::instance().unregisterDeferredObserver(observerProxy);
-            }
         }
 
         if (disconnect) {
@@ -173,18 +172,22 @@ namespace QuantLib {
 
     void Observable::notifyObservers() {
         if (ObservableSettings::instance().updatesEnabled()) {
-            return (*sig_)();
+            sig_->operator()();
         }
+        else {
+            bool updatesEnabled = false;
+            {
+                std::lock_guard<std::mutex> sLock(ObservableSettings::instance().mutex_);
+                updatesEnabled = ObservableSettings::instance().updatesEnabled();
+
+                if (ObservableSettings::instance().updatesDeferred()) {
+                    std::lock_guard<std::recursive_mutex> lock(mutex_);
+                    ObservableSettings::instance().registerDeferredObservers(observers_);
+                }
+            }
 
-        std::lock_guard<std::mutex> sLock(ObservableSettings::instance().mutex_);
-        if (ObservableSettings::instance().updatesEnabled()) {
-            return (*sig_)();
-        }
-        else if (ObservableSettings::instance().updatesDeferred()) {
-            std::lock_guard<std::recursive_mutex> lock(mutex_);
-            // if updates are only deferred, flag this for later notification
-            // these are held centrally by the settings singleton
-            ObservableSettings::instance().registerDeferredObservers(observers_);
+            if (updatesEnabled)
+                sig_->operator()();
         }
     }
 

diff --git a/ql/patterns/observable.hpp b/ql/patterns/observable.hpp
@@ -262,7 +262,9 @@ namespace QuantLib {
 
 #else
 
+#ifndef QL_USE_STD_SHARED_PTR
 #include <boost/smart_ptr/owner_less.hpp>
+#endif
 #include <atomic>
 #include <mutex>
 #include <set>
@@ -401,7 +403,7 @@ namespace QuantLib {
       public:
         void disableUpdates(bool deferred=false) {
             std::lock_guard<std::mutex> lock(mutex_);
-            updatesType_ = (deferred) ? UpdatesDeferred : 0;
+            updatesType_ = (deferred) ? UpdatesDeferred : UpdatesDisabled;
         }
         void enableUpdates();
 
@@ -410,17 +412,23 @@ namespace QuantLib {
       private:
         ObservableSettings() : updatesType_(UpdatesEnabled) {}
 
+#if defined(QL_USE_STD_SHARED_PTR)
+        typedef std::set<ext::weak_ptr<Observer::Proxy>,
+                         std::owner_less<ext::weak_ptr<Observer::Proxy> > >
+            set_type;
+#else
         typedef std::set<ext::weak_ptr<Observer::Proxy>,
                          boost::owner_less<ext::weak_ptr<Observer::Proxy> > >
             set_type;
+#endif
 
         void registerDeferredObservers(const Observable::set_type& observers);
         void unregisterDeferredObserver(const ext::shared_ptr<Observer::Proxy>& proxy);
 
         set_type deferredObservers_;
         mutable std::mutex mutex_;
 
-        enum UpdateType { UpdatesEnabled = 1, UpdatesDeferred = 2} ;
+        enum UpdateType { UpdatesDisabled = 0, UpdatesEnabled = 1, UpdatesDeferred = 2} ;
         std::atomic<int> updatesType_;
     };