From c8ecacc046492399b13719578c8f39b1b67e08b7 Mon Sep 17 00:00:00 2001
From: Evan Rosky <erosky@google.com>
Date: Wed, 1 Mar 2023 18:35:04 -0800
Subject: [PATCH] Fix potential deadlock in transactions

It was possible to hit a deadlock scenario when using the
waitAsyncStart utility. Since that was using the main handler
for unlocked work, if the transaction was applied from the
main handler thread, it would deadlock (this happens when
transactions are queued-up on syncengine). This adds a check
and will run the uncommon queued launches on anim-thread
(which is 1 higher priority).

This also has the waitAsyncStart function actually return
the result so that we can properly observe the effects of
a PendingIntent

Bug: 271317661
Bug: 267738124
Test: System still runs and tests pass.
Change-Id: If99668b71cafe016b1ab2aad501c53d246e2877d
---
 .../server/wm/WindowOrganizerController.java  | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/services/core/java/com/android/server/wm/WindowOrganizerController.java b/services/core/java/com/android/server/wm/WindowOrganizerController.java
index 8e22821820a1f..b9cb59a17a2ef 100644
--- a/services/core/java/com/android/server/wm/WindowOrganizerController.java
+++ b/services/core/java/com/android/server/wm/WindowOrganizerController.java
@@ -74,7 +74,9 @@ import android.graphics.Point;
 import android.graphics.Rect;
 import android.os.Binder;
 import android.os.Bundle;
+import android.os.Handler;
 import android.os.IBinder;
+import android.os.Looper;
 import android.os.Parcel;
 import android.os.RemoteException;
 import android.util.AndroidRuntimeException;
@@ -998,11 +1000,14 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
                     activityOptions.setCallerDisplayId(DEFAULT_DISPLAY);
                 }
                 final Bundle options = activityOptions != null ? activityOptions.toBundle() : null;
-                waitAsyncStart(() -> mService.mAmInternal.sendIntentSender(
+                int res = waitAsyncStart(() -> mService.mAmInternal.sendIntentSender(
                         hop.getPendingIntent().getTarget(),
                         hop.getPendingIntent().getWhitelistToken(), 0 /* code */,
                         hop.getActivityIntent(), resolvedType, null /* finishReceiver */,
                         null /* requiredPermission */, options));
+                if (ActivityManager.isStartResultSuccessful(res)) {
+                    effects |= TRANSACT_EFFECTS_LIFECYCLE;
+                }
                 break;
             }
             case HIERARCHY_OP_TYPE_START_SHORTCUT: {
@@ -1353,9 +1358,16 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
      * Post and wait for the result of the activity start to prevent potential deadlock against
      * {@link WindowManagerGlobalLock}.
      */
-    private void waitAsyncStart(IntSupplier startActivity) {
+    private int waitAsyncStart(IntSupplier startActivity) {
         final Integer[] starterResult = {null};
-        mService.mH.post(() -> {
+        final Handler handler = (Looper.myLooper() == mService.mH.getLooper())
+                // uncommon case where a queued transaction is trying to start an activity. We can't
+                // post to our own thread and wait (otherwise we deadlock), so use anim thread
+                // instead (which is 1 higher priority).
+                ? mService.mWindowManager.mAnimationHandler
+                // Otherwise just put it on main handler
+                : mService.mH;
+        handler.post(() -> {
             try {
                 starterResult[0] = startActivity.getAsInt();
             } catch (Throwable t) {
@@ -1372,6 +1384,7 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
             } catch (InterruptedException ignored) {
             }
         }
+        return starterResult[0];
     }
 
     private int sanitizeAndApplyHierarchyOp(WindowContainer container,