Merge "Fix deadlock between WMGlobal and WMS" into main

2 files changed, 25 insertions, 2 deletions

diff --git a/core/java/android/view/WindowManagerGlobal.java b/core/java/android/view/WindowManagerGlobal.java
index c49fce5b558f..848261db45bd 100644
--- a/core/java/android/view/WindowManagerGlobal.java
+++ b/core/java/android/view/WindowManagerGlobal.java
@@ -179,9 +179,29 @@ public final class WindowManagerGlobal {
         }
     }
 
+    /**
+     * Sets {@link com.android.server.wm.WindowManagerService} for the system process.
+     * <p>
+     * It is needed to prevent possible deadlock. A possible scenario is:
+     * In system process, WMS holds {@link com.android.server.wm.WindowManagerGlobalLock} to call
+     * {@code WindowManagerGlobal} APIs and wait to lock {@code WindowManagerGlobal} itself
+     * (i.e. call {@link #getWindowManagerService()} in the global lock), while
+     * another component may lock {@code WindowManagerGlobal} and wait to lock
+     * {@link com.android.server.wm.WindowManagerGlobalLock}(i.e call {@link #addView} in the
+     * system process, which calls to {@link com.android.server.wm.WindowManagerService} API
+     * directly).
+     */
+    public static void setWindowManagerServiceForSystemProcess(@NonNull IWindowManager wms) {
+        sWindowManagerService = wms;
+    }
+
     @Nullable
     @UnsupportedAppUsage
     public static IWindowManager getWindowManagerService() {
+        if (sWindowManagerService != null) {
+            // Use WMS directly without locking WMGlobal to prevent deadlock.
+            return sWindowManagerService;
+        }
         synchronized (WindowManagerGlobal.class) {
             if (sWindowManagerService == null) {
                 sWindowManagerService = IWindowManager.Stub.asInterface(
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 57448cb34a43..366e1bb1f040 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -1114,8 +1114,11 @@ public class WindowManagerService extends IWindowManager.Stub
     public static WindowManagerService main(final Context context, final InputManagerService im,
             final boolean showBootMsgs, WindowManagerPolicy policy,
             ActivityTaskManagerService atm) {
-        return main(context, im, showBootMsgs, policy, atm, new DisplayWindowSettingsProvider(),
-                SurfaceControl.Transaction::new, SurfaceControl.Builder::new);
+        final WindowManagerService wms = main(context, im, showBootMsgs, policy, atm,
+                new DisplayWindowSettingsProvider(), SurfaceControl.Transaction::new,
+                SurfaceControl.Builder::new);
+        WindowManagerGlobal.setWindowManagerServiceForSystemProcess(wms);
+        return wms;
     }
 
     /**