Re: [PATCH 2/2] migration: Fix return-path thread exit

[Fabiano Rosas <farosas@suse.de>]

Cédric Le Goater <clg@redhat.com> writes:

> In case of error, close_return_path_on_source() can perform a shutdown
> to exit the return-path thread.  However, in migrate_fd_cleanup(),
> 'to_dst_file' is closed before calling close_return_path_on_source()
> and the shutdown fails, leaving the source and destination waiting for
> an event to occur.

At close_return_path_on_source, qemu_file_shutdown() and checking
ms->to_dst_file are done under the qemu_file_lock, so how could
migrate_fd_cleanup() have cleared the pointer but the ms->to_dst_file
check have passed?

>
> Close the file after calling close_return_path_on_source() so that the
> shutdown succeeds and the return-path thread exits.
>
> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> ---
>  migration/migration.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 2c3362235c7651c11d581f3c3639571f1f9636ef..1e0b6acaedc272e8ce26ad40be2c42177f5fd14e 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1314,6 +1314,7 @@ void migrate_set_state(int *state, int old_state, int new_state)
>  static void migrate_fd_cleanup(MigrationState *s)
>  {
>      int file_error = 0;
> +    QEMUFile *tmp = NULL;
>  
>      g_free(s->hostname);
>      s->hostname = NULL;
> @@ -1323,8 +1324,6 @@ static void migrate_fd_cleanup(MigrationState *s)
>      qemu_savevm_state_cleanup();
>  
>      if (s->to_dst_file) {
> -        QEMUFile *tmp;
> -
>          trace_migrate_fd_cleanup();
>          bql_unlock();
>          if (s->migration_thread_running) {
> @@ -1344,15 +1343,14 @@ static void migrate_fd_cleanup(MigrationState *s)
>           * critical section won't block for long.
>           */
>          migration_ioc_unregister_yank_from_file(tmp);
> -        qemu_fclose(tmp);
>      }
>  
> -    /*
> -     * We already cleaned up to_dst_file, so errors from the return
> -     * path might be due to that, ignore them.
> -     */
>      close_return_path_on_source(s, file_error);
>  
> +    if (tmp) {
> +        qemu_fclose(tmp);
> +    }
> +
>      assert(!migration_is_active(s));
>  
>      if (s->state == MIGRATION_STATUS_CANCELLING) {