Commit 11ec828e authored Jan 12, 2022 by Sergey Nikolaienkov

Make IOnAssociationsChangedListener.onAssociationsChanged() blocking

Make IOnAssociationsChangedListener.onAssociationsChanged() blocking
(not "oneway") to make sure that the clients of the
addOnAssociationsChangedListener() API (@SystemAPI guarded by a
"signature" permission) are able to prevent race conditions that may
arise if their own clients (applications) effectively get notified
about the changes before system services do.

This is safe for 2 reasons:
1. The addOnAssociationsChangedListener() API is only available to the
   system components (guarded by a "signature" permission).
   See android.permission.MANAGE_COMPANION_DEVICES.
2. On the Java side addOnAssociationsChangedListener() in CDM takes an
   Executor, and the proxy implementation of onAssociationsChanged()
   simply "posts" a job to it.
   See CompanionDeviceManager.OnAssociationsChangedListenerProxy class.

Bug: 214016641
Test: atest --iterations 10 CtsCompanionDeviceManagerCoreTestCases:AssociationsChangedListenerTest
Test: atest CtsCompanionDeviceManagerCoreTestCases
Test: atest CtsCompanionDeviceManagerUiAutomationTestCases
Test: atest CtsOsTestCases:CompanionDeviceManagerTest
Change-Id: I7c664e9b9c848f8f0291ff46a56ff47bae7db346

parent bac69433

core/java/android/companion/IOnAssociationsChangedListener.aidl

+18 −1

Original line number	Diff line number	Diff line
		@@ -20,5 +20,22 @@ import android.companion.AssociationInfo;

		/** @hide */
		interface IOnAssociationsChangedListener {
		oneway void onAssociationsChanged(in List<AssociationInfo> associations);

		/*
		* IMPORTANT: This method is intentionally NOT "oneway".
		*
		* The method is intentionally "blocking" to make sure that the clients of the
		* addOnAssociationsChangedListener() API (@SystemAPI guarded by a "signature" permission) are
		* able to prevent race conditions that may arise if their own clients (applications)
		* effectively get notified about the changes before system services do.
		*
		* This is safe for 2 reasons:
		* 1. The addOnAssociationsChangedListener() is only available to the system components
		* (guarded by a "signature" permission).
		* See android.permission.MANAGE_COMPANION_DEVICES.
		* 2. On the Java side addOnAssociationsChangedListener() in CDM takes an Executor, and the
		* proxy implementation of onAssociationsChanged() simply "post" a Runnable to it.
		* See CompanionDeviceManager.OnAssociationsChangedListenerProxy class.
		*/
		void onAssociationsChanged(in List<AssociationInfo> associations);
		}
		No newline at end of file