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Re: [PATCH for 6.1] multifd: Unconditionally unregister yank function
From: |
Lukas Straub |
Subject: |
Re: [PATCH for 6.1] multifd: Unconditionally unregister yank function |
Date: |
Wed, 4 Aug 2021 20:13:23 +0000 |
On Wed, 4 Aug 2021 15:39:55 -0400
Peter Xu <peterx@redhat.com> wrote:
> On Wed, Aug 04, 2021 at 09:26:32PM +0200, Lukas Straub 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().
>
> Curious whether there was a crash somewhere that you hit?
No, I just noticed this while working on a different patch.
> > 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.
>
> Thanks for checking and removing the 2nd ref==1. I wanted to do that but I
> didn't dare before I look more closely or test more.
>
> The patch looks good to me, it's just that I am not sure whether it suites 6.1
> material as we've just released rc2 today. Maybe 6.2 is more suitable?
Yeah, if my assessment of the code is correct it's more of a cleanup.
> >
> > 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);
> > --
> > 2.32.0
>
>
>
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