Check if the trace was stopped before starting the tracing thread

If a winscope trace is started and stopped quickly, the tracing thread
will not be stopped. The tracing thread waits for a conditional variable
notification that is sent before the thread starts running. To fix the
issue, properly initialize the trace enabled variable in the tracing
thread.

Test: atest FlickerLibTest:LayersTraceMonitorTest
Fixes: 153206487
Change-Id: I0c591c1fc3209327b40323b3ebb4fa4279c6ed05

2 files changed, 4 insertions, 5 deletions

diff --git a/services/surfaceflinger/SurfaceTracing.cpp b/services/surfaceflinger/SurfaceTracing.cpp
index a9c33327c8..68ecfd1b83 100644
--- a/services/surfaceflinger/SurfaceTracing.cpp
+++ b/services/surfaceflinger/SurfaceTracing.cpp
@@ -36,22 +36,21 @@ SurfaceTracing::SurfaceTracing(SurfaceFlinger& flinger)
       : mFlinger(flinger), mSfLock(flinger.mDrawingStateLock) {}
 
 void SurfaceTracing::mainLoop() {
-    addFirstEntry();
-    bool enabled = true;
+    bool enabled = addFirstEntry();
     while (enabled) {
         LayersTraceProto entry = traceWhenNotified();
         enabled = addTraceToBuffer(entry);
     }
 }
 
-void SurfaceTracing::addFirstEntry() {
+bool SurfaceTracing::addFirstEntry() {
     const auto displayDevice = mFlinger.getDefaultDisplayDevice();
     LayersTraceProto entry;
     {
         std::scoped_lock lock(mSfLock);
         entry = traceLayersLocked("tracing.enable", displayDevice);
     }
-    addTraceToBuffer(entry);
+    return addTraceToBuffer(entry);
 }
 
 LayersTraceProto SurfaceTracing::traceWhenNotified() {
diff --git a/services/surfaceflinger/SurfaceTracing.h b/services/surfaceflinger/SurfaceTracing.h
index 83872ed3ae..5dae1697dd 100644
--- a/services/surfaceflinger/SurfaceTracing.h
+++ b/services/surfaceflinger/SurfaceTracing.h
@@ -85,7 +85,7 @@ private:
     };
 
     void mainLoop();
-    void addFirstEntry();
+    bool addFirstEntry();
     LayersTraceProto traceWhenNotified();
     LayersTraceProto traceLayersLocked(const char* where,
                                        const sp<const DisplayDevice>& displayDevice)