Merge "Allow DiskRead ThreadPolicy in LetterboxConfigurationPersister" into udc-dev

services/core/java/com/android/server/wm/LetterboxConfigurationPersister.java

@@ -16,6 +16,8 @@
 
 package com.android.server.wm;
 
+import static android.os.StrictMode.setThreadPolicy;
+
 import static com.android.server.wm.WindowManagerDebugConfig.TAG_WITH_CLASS_NAME;
 import static com.android.server.wm.WindowManagerDebugConfig.TAG_WM;
 
@@ -23,6 +25,8 @@ import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.content.Context;
 import android.os.Environment;
+import android.os.StrictMode;
+import android.os.StrictMode.ThreadPolicy;
 import android.util.AtomicFile;
 import android.util.Slog;
 
@@ -125,7 +129,7 @@ class LetterboxConfigurationPersister {
         final File prefFiles = new File(configFolder, LETTERBOX_CONFIGURATION_FILENAME);
         mConfigurationFile = new AtomicFile(prefFiles);
         mPersisterQueue = persisterQueue;
-        readCurrentConfiguration();
+        runWithDiskReadsThreadPolicy(this::readCurrentConfiguration);
     }
 
     /**
@@ -275,6 +279,20 @@ class LetterboxConfigurationPersister {
         }
     }
 
+    // The LetterboxConfigurationDeviceConfig needs to access the
+    // file with the current reachability position once when the
+    // device boots. Because DisplayThread uses allowIo=false
+    // accessing a file triggers a DiskReadViolation.
+    // Here we use StrictMode to allow the current thread to read
+    // the AtomicFile once in the current thread restoring the
+    // original ThreadPolicy after that.
+    private void runWithDiskReadsThreadPolicy(Runnable runnable) {
+        final ThreadPolicy currentPolicy = StrictMode.getThreadPolicy();
+        setThreadPolicy(new ThreadPolicy.Builder().permitDiskReads().build());
+        runnable.run();
+        setThreadPolicy(currentPolicy);
+    }
+
     private static class UpdateValuesCommand implements
             PersisterQueue.WriteQueueItem<UpdateValuesCommand> {