From fdb718f300e96266a521c48c7e1d273d70350ac7 Mon Sep 17 00:00:00 2001
From: Nikolas Havrikov <havrikov@google.com>
Date: Mon, 27 Sep 2021 08:27:21 +0000
Subject: [PATCH] Enable lowering IME binding priority

This CL introduces the config_killableInputMethods
configuration option, which is disabled by default.
When enabled, this option lowers the IME binding priority
to below the perceptible level to allow the lowmemorykiller
to reclaim the IME process.

Test: set the config value to true in an overlay
Test: manually on an Android TV device
Test atest CtsInputMethodTestCases
Bug: 199887357

Change-Id: Ib191d964de15bbb84daa8bbeca6f2dca6f96311c
---
 core/res/res/values/config.xml                |  3 ++
 core/res/res/values/symbols.xml               |  1 +
 .../InputMethodManagerService.java            | 32 +++++++++++++++++--
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/core/res/res/values/config.xml b/core/res/res/values/config.xml
index f1a961d7cd1ac..e66f5247499ce 100644
--- a/core/res/res/values/config.xml
+++ b/core/res/res/values/config.xml
@@ -2781,6 +2781,9 @@
         <item>com.android.inputmethod.latin</item>
     </string-array>
 
+    <!-- Make the IME killable by the lowmemorykiller by raising its oom_score_adj. -->
+    <bool name="config_killableInputMethods">false</bool>
+
     <!-- The list of classes that should be added to the notification ranking pipeline.
      See {@link com.android.server.notification.NotificationSignalExtractor}
       If you add a new extractor to this list make sure to update
diff --git a/core/res/res/values/symbols.xml b/core/res/res/values/symbols.xml
index 0587474fc0543..752f914bdb1fe 100644
--- a/core/res/res/values/symbols.xml
+++ b/core/res/res/values/symbols.xml
@@ -2228,6 +2228,7 @@
   <java-symbol type="string" name="config_secondaryLocationTimeZoneProviderPackageName" />
   <java-symbol type="bool" name="config_autoResetAirplaneMode" />
   <java-symbol type="string" name="config_notificationAccessConfirmationActivity" />
+  <java-symbol type="bool" name="config_killableInputMethods" />
 
   <java-symbol type="layout" name="resolver_list" />
   <java-symbol type="id" name="resolver_list" />
diff --git a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
index 075b74d5bbdca..5b739d668e63b 100644
--- a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
@@ -269,6 +269,24 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
             | Context.BIND_NOT_FOREGROUND
             | Context.BIND_IMPORTANT_BACKGROUND;
 
+    /**
+     * Binding flags for establishing connection to the {@link InputMethodService} when
+     * config_killableInputMethods is enabled.
+     */
+    private static final int IME_CONNECTION_LOW_PRIORITY_BIND_FLAGS =
+            Context.BIND_AUTO_CREATE
+            | Context.BIND_REDUCTION_FLAGS;
+
+    /**
+     * Binding flags for establishing connection to the {@link InputMethodService}.
+     *
+     * <p>
+     * This defaults to {@link #IME_CONNECTION_BIND_FLAGS} unless config_killableInputMethods is
+     * enabled, in which case this takes the value of
+     * {@link #IME_CONNECTION_LOW_PRIORITY_BIND_FLAGS}.
+     */
+    private final int mImeConnectionBindFlags;
+
     /**
      * Binding flags used only while the {@link InputMethodService} is showing window.
      */
@@ -1651,6 +1669,16 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
         mSwitchingController = InputMethodSubtypeSwitchingController.createInstanceLocked(
                 mSettings, context);
         mMenuController = new InputMethodMenuController(this);
+
+        // If configured, use low priority flags to make the IME killable by the lowmemorykiller
+        final boolean lowerIMEPriority = mRes.getBoolean(
+                com.android.internal.R.bool.config_killableInputMethods);
+
+        if (lowerIMEPriority) {
+            mImeConnectionBindFlags = IME_CONNECTION_LOW_PRIORITY_BIND_FLAGS;
+        } else {
+            mImeConnectionBindFlags = IME_CONNECTION_BIND_FLAGS;
+        }
     }
 
     @GuardedBy("mMethodMap")
@@ -2434,7 +2462,7 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
                 mContext, 0, new Intent(Settings.ACTION_INPUT_METHOD_SETTINGS),
                 PendingIntent.FLAG_IMMUTABLE));
 
-        if (bindCurrentInputMethodServiceLocked(mCurIntent, this, IME_CONNECTION_BIND_FLAGS)) {
+        if (bindCurrentInputMethodServiceLocked(mCurIntent, this, mImeConnectionBindFlags)) {
             mLastBindTime = SystemClock.uptimeMillis();
             mHaveConnection = true;
             mCurId = info.getId();
@@ -3155,7 +3183,7 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
                     SystemClock.uptimeMillis()-mLastBindTime,1);
             Slog.w(TAG, "Force disconnect/connect to the IME in showCurrentInputLocked()");
             mContext.unbindService(this);
-            bindCurrentInputMethodServiceLocked(mCurIntent, this, IME_CONNECTION_BIND_FLAGS);
+            bindCurrentInputMethodServiceLocked(mCurIntent, this, mImeConnectionBindFlags);
         } else {
             if (DEBUG) {
                 Slog.d(TAG, "Can't show input: connection = " + mHaveConnection + ", time = "