audio_core: sink_stream: Hold the suspend lock when process is stalled.

- Prevents us from clashing with other callers trying to un/stall.

src/audio_core/sink/sink_stream.cpp

@@ -266,19 +266,20 @@ void SinkStream::ProcessAudioOutAndRender(std::span<s16> output_buffer, std::siz
 }
 
 void SinkStream::Stall() {
-    if (stalled) {
+    std::scoped_lock lk{stall_guard};
+    if (stalled_lock) {
         return;
     }
-    stalled = true;
-    system.StallProcesses();
+    stalled_lock = system.StallProcesses();
 }
 
 void SinkStream::Unstall() {
-    if (!stalled) {
+    std::scoped_lock lk{stall_guard};
+    if (!stalled_lock) {
         return;
     }
     system.UnstallProcesses();
-    stalled = false;
+    stalled_lock.unlock();
 }
 
 } // namespace AudioCore::Sink

src/audio_core/sink/sink_stream.h

@@ -6,6 +6,7 @@
 #include <array>
 #include <atomic>
 #include <memory>
+#include <mutex>
 #include <span>
 #include <vector>
 
@@ -240,8 +241,8 @@ private:
     f32 system_volume{1.0f};
     /// Set via IAudioDevice service calls
     f32 device_volume{1.0f};
-    /// True if coretiming has been stalled
-    bool stalled{false};
+    std::mutex stall_guard;
+    std::unique_lock<std::mutex> stalled_lock;
 };
 
 using SinkStreamPtr = std::unique_ptr<SinkStream>;