Re: [PATCH v2 26/39] tests/qtest: migration-test: Make sure QEMU process "to" exited after migration is canceled

[Dr. David Alan Gilbert]

* Bin Meng (bmeng.cn@gmail.com) wrote:
> From: Xuzhou Cheng <xuzhou.cheng@windriver.com>
> 
> Make sure QEMU process "to" exited before launching another target
> for migration in the test_multifd_tcp_cancel case.
> 
> Signed-off-by: Xuzhou Cheng <xuzhou.cheng@windriver.com>
> Signed-off-by: Bin Meng <bin.meng@windriver.com>
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

Hmm you might want to put a small usleep in that loop; otherwise
it'll burn CPU.

There is a slim risk with this that another, entirely unrelated, process 
will start up with the same PID between the end of migrate_cancel
and then you'll be spinning on it rather than the 'to' qemu.

I wonder if there's a better way to check for it dieing; e.g. an error
on it's qmp interface or something?

Dave

> ---
> 
> Changes in v2:
> - Change to a busy wait after migration is canceled
> 
>  tests/qtest/migration-test.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index c87afad9e8..aedd9ddb72 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -2133,6 +2133,10 @@ static void test_multifd_tcp_cancel(void)
>      wait_for_migration_pass(from);
>  
>      migrate_cancel(from);
> +    /* Make sure QEMU process "to" exited */
> +    while (qtest_probe_child(to)) {
> +        ;
> +    }
>  
>      args = (MigrateStart){
>          .only_target = true,
> -- 
> 2.34.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK