commit 0aea1f3800edf779e97f7e36be095e1d9d39b768
author Massimo Carli <mcarli@google.com> Tue Jun 20 20:16:46 2023 +0000
committer Massimo Carli <mcarli@google.com> Wed Jun 21 04:49:34 2023 +0000
tree db0fa1533d6943234de4c6791e3c1d992d0ba1ef
parent 01158d6e178a922da415d6fc34a787973c1fb1e2

Allow DiskRead ThreadPolicy in 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.

Fix: 286620565
Test: Run `atest WmTests:LetterboxConfigurationDeviceConfigTests`

Change-Id: Ia358de8c817eea987547c82df0ea8612591c0600

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

diff --git a/services/core/java/com/android/server/wm/LetterboxConfigurationPersister.java b/services/core/java/com/android/server/wm/LetterboxConfigurationPersister.java
index 3b10deb..7563397 100644
--- a/services/core/java/com/android/server/wm/LetterboxConfigurationPersister.java
+++ b/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.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 @@
         final File prefFiles = new File(configFolder, LETTERBOX_CONFIGURATION_FILENAME);
         mConfigurationFile = new AtomicFile(prefFiles);
         mPersisterQueue = persisterQueue;
-        readCurrentConfiguration();
+        runWithDiskReadsThreadPolicy(this::readCurrentConfiguration);
     }
 
     /**
@@ -275,6 +279,20 @@
         }
     }
 
+    // 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> {