Make sure to not block SystemService#onUserStarting() in IMMS

As part of our on-going effort to make sure that slow I/O operations
will not block the system in InputMethodManagerService, we start
dispatching

  InputMethodManagerService#initializeVisibleBackgroundUserLocked()

into an I/O thread.

The observable semantics should remain unchanged in general.

Bug: 343601565
Test: presubmit
Flag: EXEMPT refactor
Change-Id: Iee0b1c7276f88e4b179b0eb8fb978503bc45760c

1 files changed, 7 insertions, 5 deletions

diff --git a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
index f84d55f9b20b..7daf9582cdd6 100644
--- a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
@@ -1038,13 +1038,15 @@ public final class InputMethodManagerService implements IInputMethodManagerImpl.
             // Called on ActivityManager thread.
             final int userId = user.getUserIdentifier();
             SecureSettingsWrapper.onUserStarting(userId);
-            synchronized (ImfLock.class) {
-                if (mService.mConcurrentMultiUserModeEnabled) {
-                    if (mService.mCurrentUserId != userId && mService.mSystemReady) {
-                        mService.initializeVisibleBackgroundUserLocked(userId);
+            mService.mIoHandler.post(() -> {
+                synchronized (ImfLock.class) {
+                    if (mService.mConcurrentMultiUserModeEnabled) {
+                        if (mService.mCurrentUserId != userId && mService.mSystemReady) {
+                            mService.initializeVisibleBackgroundUserLocked(userId);
+                        }
                     }
                 }
-            }
+            });
         }
 
     }