Re: [PATCH for 6.1] multifd: Unconditionally unregister yank function

[Lukas Straub]

On Wed, 4 Aug 2021 21:26:32 +0200
Lukas Straub <lukasstraub2@web.de> wrote:

> Unconditionally unregister yank function in multifd_load_cleanup().
> If it is not unregistered here, it will leak and cause a crash
> in yank_unregister_instance(). Now if the ioc is still in use
> afterwards, it will only lead to qemu not being able to recover
> from a hang related to that ioc.
> 
> After checking the code, i am pretty sure that ref is always 1
> when arriving here. So all this currently does is remove the
> unneeded check.
> 
> Signed-off-by: Lukas Straub <lukasstraub2@web.de>
> ---
> 
> This is similar to Peter Xu's 
> 39675ffffb3394d44b880d083a214c5e44786170
> "migration: Move the yank unregister of channel_close out"
> in that it removes the "OBJECT(p->c)->ref == 1" hack. So it
> makes sense for 6.1 so these patches are together.
> 
>  migration/multifd.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 377da78f5b..a37805e17e 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -987,10 +987,7 @@ int multifd_load_cleanup(Error **errp)
>      for (i = 0; i < migrate_multifd_channels(); i++) {
>          MultiFDRecvParams *p = &multifd_recv_state->params[i];
>  
> -        if (OBJECT(p->c)->ref == 1) {
> -            migration_ioc_unregister_yank(p->c);
> -        }
> -
> +        migration_ioc_unregister_yank(p->c);
>          object_unref(OBJECT(p->c));
>          p->c = NULL;
>          qemu_mutex_destroy(&p->mutex);

ping...

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