Fix race conditions for lazy services.

Add hidlFqName/hidlName to registerClientCallbacks to make it more
explicit, provide better errors, and for general sanity.

Add tryUnregister so that a service can unregister itself before
shutting down.

Bug: 123318663
Test: hidl_test, manual

Change-Id: I3ee26ba96dbc9732e72aaa16281abc47ce6a02c9
Merged-In: I3ee26ba96dbc9732e72aaa16281abc47ce6a02c9

2 files changed, 36 insertions, 3 deletions

diff --git a/transport/manager/1.2/IClientCallback.hal b/transport/manager/1.2/IClientCallback.hal
index 1189e44..8ebb044 100644
--- a/transport/manager/1.2/IClientCallback.hal
+++ b/transport/manager/1.2/IClientCallback.hal
@@ -21,6 +21,10 @@ interface IClientCallback {
      * This is called when there is a transition between having >= 1 clients and having 0 clients
      * (or vice versa).
      *
+     * Upon receiving hasClients false, if the process decides to exit, it is recommended to try to
+     * unregister using @1.2::IServiceManager's tryUnregister before quiting in case another client
+     * associates.
+     *
      * @param registered binder 'server' registered with IServiceManager's registerClientCallback
      * @param hasClients whether there are currently clients
      *     true - when there are >= 1 clients. This must be called as soon as IServiceManager::get
diff --git a/transport/manager/1.2/IServiceManager.hal b/transport/manager/1.2/IServiceManager.hal
index e1629d6..d79403d 100644
--- a/transport/manager/1.2/IServiceManager.hal
+++ b/transport/manager/1.2/IServiceManager.hal
@@ -27,7 +27,9 @@ interface IServiceManager extends @1.1::IServiceManager {
      * If the service has clients at the time of registration, the callback is called with
      * hasClients true. After that, it is called based on the changes in clientele.
      *
-     * @param server non-null service waiting to have no clients
+     * @param fqName Fully-qualified interface name (used to register)
+     * @param name Instance name (of the registered service)
+     * @param server non-null service waiting to have no clients (previously registered)
      * @param cb non-null callback to call when there are no clients
      * @return success
      *     true on success
@@ -35,7 +37,11 @@ interface IServiceManager extends @1.1::IServiceManager {
      *      - the server or cb parameters are null
      *      - this is called by a process other than the server process
      */
-    registerClientCallback(interface server, IClientCallback cb) generates (bool success);
+    registerClientCallback(string fqName,
+                           string name,
+                           interface server,
+                           IClientCallback cb)
+        generates (bool success);
 
     /**
      * Removes a callback previously registered with registerClientCallback.
@@ -68,9 +74,32 @@ interface IServiceManager extends @1.1::IServiceManager {
      *
      * See also @1.0::IServiceManager's listByInterface function.
      *
-     * @param fqName         Fully-qualified interface name.
+     * @param fqName Fully-qualified interface name.
      *
      * @return instanceNames List of instance names running the particular service.
      */
     listManifestByInterface(string fqName) generates (vec<string> instanceNames);
+
+    /**
+     * Unregisters a service if there are no clients for it. This must only unregister the
+     * service if it is called from the same process that registered the service.
+     *
+     * This unregisters all instances of the service, even if they are under a different instance
+     * name.
+     *
+     * Recommended usage is when creating a lazy process, try unregistering when IClientCallback's
+     * onClients(*, false) is called. If this unregister is successful, then it is safe to exit. If
+     * it is unsuccessful, then you can assume a client re-associated with the server. If a process
+     * has multiple servers, and only some succeed in unregistration, then the unregistered services
+     * can be re-registered.
+     *
+     * See also addWithChain and @1.0::IServiceManager's add.
+     *
+     * @param fqName Fully-qualified interface name.
+     * @param name Instance name.
+     * @param service Handle to registering service.
+     *
+     * @return success Whether the service was successfully unregistered.
+     */
+    tryUnregister(string fqName, string name, interface service) generates (bool success);
 };