[PATCH V2] migration: simplify notifiers

[Steve Sistare <steven.sistare@oracle.com>]

Pass the callback function to add_migration_state_change_notifier so
that migration can initialize the notifier on add and clear it on
delete, which simplifies the call sites.  Shorten the function names
so the extra arg can be added more legibly.  Hide the global notifier
list in a new function migration_call_notifiers, and make it externally
visible so future cpr code can call it.

No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 hw/net/virtio-net.c      |  6 +++---
 hw/vfio/migration.c      |  6 +++---
 include/migration/misc.h |  6 ++++--
 migration/migration.c    | 22 ++++++++++++++++------
 ui/spice-core.c          |  3 +--
 5 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 3ae9090..4a44f99 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3570,8 +3570,8 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
         n->primary_listener.hide_device = failover_hide_primary_device;
         qatomic_set(&n->failover_primary_hidden, true);
         device_listener_register(&n->primary_listener);
-        n->migration_state.notify = virtio_net_migration_state_notifier;
-        add_migration_state_change_notifier(&n->migration_state);
+        migration_add_notifier(&n->migration_state,
+                               virtio_net_migration_state_notifier);
         n->host_features |= (1ULL << VIRTIO_NET_F_STANDBY);
     }
 
@@ -3734,7 +3734,7 @@ static void virtio_net_device_unrealize(DeviceState *dev)
     if (n->failover) {
         qobject_unref(n->primary_opts);
         device_listener_unregister(&n->primary_listener);
-        remove_migration_state_change_notifier(&n->migration_state);
+        migration_remove_notifier(&n->migration_state);
     } else {
         assert(n->primary_opts == NULL);
     }
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index d149176..8897b48 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -841,8 +841,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
     migration->vm_state = qdev_add_vm_change_state_handler(vbasedev->dev,
                                                            vfio_vmstate_change,
                                                            vbasedev);
-    migration->migration_state.notify = vfio_migration_state_notifier;
-    add_migration_state_change_notifier(&migration->migration_state);
+    migration_add_notifier(&migration->migration_state,
+                           vfio_migration_state_notifier);
     return 0;
 
 err:
@@ -897,7 +897,7 @@ void vfio_migration_finalize(VFIODevice *vbasedev)
     if (vbasedev->migration) {
         VFIOMigration *migration = vbasedev->migration;
 
-        remove_migration_state_change_notifier(&migration->migration_state);
+        migration_remove_notifier(&migration->migration_state);
         qemu_del_vm_change_state_handler(migration->vm_state);
         unregister_savevm(VMSTATE_IF(vbasedev->dev), "vfio", vbasedev);
         vfio_migration_exit(vbasedev);
diff --git a/include/migration/misc.h b/include/migration/misc.h
index 4659067..888fd1b 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -59,8 +59,10 @@ void migration_object_init(void);
 void migration_shutdown(void);
 bool migration_is_idle(void);
 bool migration_is_active(MigrationState *);
-void add_migration_state_change_notifier(Notifier *notify);
-void remove_migration_state_change_notifier(Notifier *notify);
+void migration_add_notifier(Notifier *notify,
+                            void (*func)(Notifier *notifier, void *data));
+void migration_remove_notifier(Notifier *notify);
+void migration_call_notifiers(MigrationState *s);
 bool migration_in_setup(MigrationState *);
 bool migration_has_finished(MigrationState *);
 bool migration_has_failed(MigrationState *);
diff --git a/migration/migration.c b/migration/migration.c
index 6c5283c..2a4894b 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1980,7 +1980,7 @@ static void migrate_fd_cleanup(MigrationState *s)
         /* It is used on info migrate.  We can't free it */
         error_report_err(error_copy(s->error));
     }
-    notifier_list_notify(&migration_state_notifiers, s);
+    migration_call_notifiers(s);
     block_cleanup_parameters(s);
     yank_unregister_instance(MIGRATION_YANK_INSTANCE);
 }
@@ -2075,14 +2075,24 @@ static void migrate_fd_cancel(MigrationState *s)
     }
 }
 
-void add_migration_state_change_notifier(Notifier *notify)
+void migration_add_notifier(Notifier *notify,
+                            void (*func)(Notifier *notifier, void *data))
 {
+    notify->notify = func;
     notifier_list_add(&migration_state_notifiers, notify);
 }
 
-void remove_migration_state_change_notifier(Notifier *notify)
+void migration_remove_notifier(Notifier *notify)
+{
+    if (notify->notify) {
+        notifier_remove(notify);
+        notify->notify = NULL;
+    }
+}
+
+void migration_call_notifiers(MigrationState *s)
 {
-    notifier_remove(notify);
+    notifier_list_notify(&migration_state_notifiers, s);
 }
 
 bool migration_in_setup(MigrationState *s)
@@ -3257,7 +3267,7 @@ static int postcopy_start(MigrationState *ms)
      * spice needs to trigger a transition now
      */
     ms->postcopy_after_devices = true;
-    notifier_list_notify(&migration_state_notifiers, ms);
+    migration_call_notifiers(ms);
 
     ms->downtime =  qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - time_at_stop;
 
@@ -4282,7 +4292,7 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
         rate_limit = s->parameters.max_bandwidth / XFER_LIMIT_RATIO;
 
         /* Notify before starting migration thread */
-        notifier_list_notify(&migration_state_notifiers, s);
+        migration_call_notifiers(s);
     }
 
     qemu_file_set_rate_limit(s->to_dst_file, rate_limit);
diff --git a/ui/spice-core.c b/ui/spice-core.c
index 72f8f16..d902d00 100644
--- a/ui/spice-core.c
+++ b/ui/spice-core.c
@@ -814,8 +814,7 @@ static void qemu_spice_init(void)
     };
     using_spice = 1;
 
-    migration_state.notify = migration_state_notifier;
-    add_migration_state_change_notifier(&migration_state);
+    migration_add_notifier(&migration_state, migration_state_notifier);
     spice_migrate.base.sif = &migrate_interface.base;
     qemu_spice.add_interface(&spice_migrate.base);
 
-- 
1.8.3.1