migration: Add postcopy_thread_create()

Postcopy create threads. A common manner is we init a sem and use it to sync
with the thread.  Namely, we have fault_thread_sem and listen_thread_sem and
they're only used for this.

Make it a shared infrastructure so it's easier to create yet another thread.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220301083925.33483-7-peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

1 files changed, 3 insertions, 9 deletions

diff --git a/migration/savevm.c b/migration/savevm.c
index 0ccd7e5e3f..967ff80547 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1863,7 +1863,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
 
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                                    MIGRATION_STATUS_POSTCOPY_ACTIVE);
-    qemu_sem_post(&mis->listen_thread_sem);
+    qemu_sem_post(&mis->thread_sync_sem);
     trace_postcopy_ram_listen_thread_start();
 
     rcu_register_thread();
@@ -1988,14 +1988,8 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
     }
 
     mis->have_listen_thread = true;
-    /* Start up the listening thread and wait for it to signal ready */
-    qemu_sem_init(&mis->listen_thread_sem, 0);
-    qemu_thread_create(&mis->listen_thread, "postcopy/listen",
-                       postcopy_ram_listen_thread, NULL,
-                       QEMU_THREAD_DETACHED);
-    qemu_sem_wait(&mis->listen_thread_sem);
-    qemu_sem_destroy(&mis->listen_thread_sem);
-
+    postcopy_thread_create(mis, &mis->listen_thread, "postcopy/listen",
+                           postcopy_ram_listen_thread, QEMU_THREAD_DETACHED);
     trace_loadvm_postcopy_handle_listen("return");
 
     return 0;