The migration thread runs outside the QEMU global mutex when possible. Therefore we must notify migration state change *before* starting the migration thread.
This allows registered listeners to act before live migration iterations begin. Therefore they can get into a state that allows for live migration. When the migration thread starts everything will be ready. Without this patch there is a race condition during migration setup, depending on whether the migration thread has already transitioned from SETUP to ACTIVE state. Acked-by: Paolo Bonzini <[email protected]> Reviewed-by: Kevin Wolf <[email protected]> Signed-off-by: Stefan Hajnoczi <[email protected]> --- migration.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/migration.c b/migration.c index e12e784..a5ed26b 100644 --- a/migration.c +++ b/migration.c @@ -658,7 +658,9 @@ void migrate_fd_connect(MigrationState *s) qemu_file_set_rate_limit(s->file, s->bandwidth_limit / XFER_LIMIT_RATIO); + /* Notify before starting migration thread */ + notifier_list_notify(&migration_state_notifiers, s); + qemu_thread_create(&s->thread, migration_thread, s, QEMU_THREAD_JOINABLE); - notifier_list_notify(&migration_state_notifiers, s); } -- 1.8.1.4
