audioinput: use a mutex to protect against async resource changes

Replaces an atomic flag with a mutex preventing async calls to
switchInput from just failing or possibly causing a crash if a
resource already in progress.

jami-client-qt#522

Change-Id: I5f726306a2d54b1dcaa396a463d221a6efca13d8

src/media/audio/audio_input.cpp

@@ -71,13 +71,6 @@ AudioInput::~AudioInput()
 void
 AudioInput::process()
 {
-    if (switchPending_.exchange(false)) {
-        if (devOpts_.input.empty())
-            JAMI_DBG() << "Switching to default audio input";
-        else
-            JAMI_DBG() << "Switching audio input to '" << devOpts_.input << "'";
-    }
-
     readFromDevice();
 }
 
@@ -110,14 +103,16 @@ AudioInput::setSeekTime(int64_t time)
 void
 AudioInput::readFromDevice()
 {
+    {
+        std::lock_guard<std::mutex> lk(resourceMutex_);
         if (decodingFile_)
             while (fileBuf_->isEmpty())
                 readFromFile();
-
         if (playingFile_) {
             readFromQueue();
             return;
         }
+    }
 
     // Note: read for device is called in an audio thread and we don't
     // want to have a loop which takes 100% of the CPU.
@@ -266,10 +261,7 @@ std::shared_future<DeviceParams>
 AudioInput::switchInput(const std::string& resource)
 {
     // Always switch inputs, even if it's the same resource, so audio will be in sync with video
-    if (switchPending_) {
-        JAMI_ERR() << "Audio switch already requested";
-        return {};
-    }
+    std::unique_lock<std::mutex> lk(resourceMutex_);
 
     JAMI_DBG() << "Switching audio source to match '" << resource << "'";
 
@@ -315,9 +307,9 @@ AudioInput::switchInput(const std::string& resource)
             foundDevOpts(devOpts_);
     }
 
-    switchPending_ = true;
     futureDevOpts_ = foundDevOpts_.get_future().share();
     wakeUp_ = std::chrono::high_resolution_clock::now() + MS_PER_PACKET;
+    lk.unlock();
     loop_.start();
     if (onSuccessfulSetup_)
         onSuccessfulSetup_(MEDIA_AUDIO, 0);

src/media/audio/audio_input.h

@@ -94,7 +94,7 @@ private:
     std::shared_ptr<RingBuffer> fileBuf_;
 
     std::string currentResource_;
-    std::atomic_bool switchPending_ {false};
+    std::mutex resourceMutex_ {};
     DeviceParams devOpts_;
     std::promise<DeviceParams> foundDevOpts_;
     std::shared_future<DeviceParams> futureDevOpts_;