scheduled_executor: make cancel/isCancelled non-blocking

Change-Id: Icddfa964f7980af5915b110745cb922adc10dba4

src/jamidht/jamiaccount.cpp

@@ -304,7 +304,7 @@ JamiAccount::~JamiAccount()
 {
     shutdownConnections();
     if (eventHandler) {
-        eventHandler->cancel();
+        eventHandler->destroy();
         eventHandler.reset();
     }
     if(peerDiscovery_){
@@ -3091,17 +3091,17 @@ JamiAccount::getLastMessages(const uint64_t& base_timestamp)
 void
 JamiAccount::checkPendingCallsTask()
 {
-    bool hasHandler = eventHandler and not eventHandler->isCancelled();
-    if (not pendingCalls_.empty() and not hasHandler) {
-        eventHandler = Manager::instance().scheduler().scheduleAtFixedRate([w = weak()] {
+    decltype(eventHandler) handler;
+    if (not pendingCalls_.empty()) {
+        handler = Manager::instance().scheduler().scheduleAtFixedRate([w = weak()] {
             if (auto this_ = w.lock())
                 return this_->handlePendingCallList();
             return false;
         }, std::chrono::milliseconds(10));
-    } else if (pendingCalls_.empty() and hasHandler) {
-        eventHandler->cancel();
-        eventHandler.reset();
     }
+    std::swap(handler, eventHandler);
+    if (handler)
+        handler->cancel();
 }
 
 void

src/scheduled_executor.h

@@ -68,22 +68,28 @@ public:
     RepeatedTask(RepeatedJob&& j) : job_(std::move(j)) {}
     bool run() {
         std::lock_guard<std::mutex> l(lock_);
-        if (job_ and not job_())
+        if (cancel_.load() or (job_ and not job_())) {
+            cancel_.store(true);
             job_ = {};
+        }
         return (bool)job_;
     }
     void cancel() {
+        cancel_.store(true);
+    }
+    void destroy() {
+        cancel();
         std::lock_guard<std::mutex> l(lock_);
         job_ = {};
     }
     bool isCancelled() const {
-        std::lock_guard<std::mutex> l(lock_);
-        return !job_;
+        return cancel_.load();
     }
 private:
     NON_COPYABLE(RepeatedTask);
-    RepeatedJob job_;
     mutable std::mutex lock_;
+    RepeatedJob job_;
+    std::atomic_bool cancel_ {false};
 };
 
 class ScheduledExecutor {