避免死锁

ZLToolKit @ 58a74f8c

-Subproject commit 69227690e1b6e63f43969aafda0263e05f41a14a
+Subproject commit 58a74f8c5ab802a0dd9fdcdcc0fe4c5a3d841964

src/Common/MediaSource.cpp

@@ -119,8 +119,15 @@ bool MediaSource::isRecording(Recorder::type type){
 }
 
 void MediaSource::for_each_media(const function<void(const MediaSource::Ptr &src)> &cb) {
+    decltype(g_mapMediaSrc) copy;
+    {
+        //拷贝g_mapMediaSrc后再遍历，考虑到是高频使用的全局单例锁，并且在上锁时会执行回调代码
+        //很容易导致多个锁交叉死锁的情况，而且该函数使用频率不高，拷贝开销相对来说是可以接受的
         lock_guard<recursive_mutex> lock(g_mtxMediaSrc);
-    for (auto &pr0 : g_mapMediaSrc) {
+        copy = g_mapMediaSrc;
+    }
+
+    for (auto &pr0 : copy) {
         for (auto &pr1 : pr0.second) {
             for (auto &pr2 : pr1.second) {
                 for (auto &pr3 : pr2.second) {

src/Extension/Frame.h

@@ -192,13 +192,17 @@ public:
     virtual ~FrameDispatcher(){}
 
     void addDelegate(const FrameWriterInterface::Ptr &delegate){
+        //_delegates_write可能多线程同时操作
         lock_guard<mutex> lck(_mtx);
-        _delegateMap.emplace(delegate.get(),delegate);
+        _delegates_write.emplace(delegate.get(),delegate);
+        _need_update = true;
     }
 
     void delDelegate(void *ptr){
+        //_delegates_write可能多线程同时操作
         lock_guard<mutex> lck(_mtx);
-        _delegateMap.erase(ptr);
+        _delegates_write.erase(ptr);
+        _need_update = true;
     }
 
     /**
@@ -206,14 +210,23 @@ public:
      * @param frame 帧
      */
     void inputFrame(const Frame::Ptr &frame) override{
-        lock_guard<mutex> lck(_mtx);
-        for(auto &pr : _delegateMap){
+        //_delegates_read能确保是单线程操作的
+        for(auto &pr : _delegates_read){
             pr.second->inputFrame(frame);
         }
+
+        if(_need_update){
+            //发现代理列表发生变化了，这里同步一次
+            lock_guard<mutex> lck(_mtx);
+            _delegates_read = _delegates_write;
+            _need_update = false;
+        }
     }
 private:
     mutex _mtx;
-    map<void *,FrameWriterInterface::Ptr>  _delegateMap;
+    map<void *,FrameWriterInterface::Ptr>  _delegates_read;
+    map<void *,FrameWriterInterface::Ptr>  _delegates_write;
+    bool _need_update = false;
 };
 
 /**