From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: qemu-devel@nongnu.org, quintela@redhat.com, alex.bennee@linaro.org
Subject: Re: [Qemu-devel] [PATCH] migration: Cleanup during exit
Date: Thu, 28 Feb 2019 11:40:19 +0000 [thread overview]
Message-ID: <20190228114019.GB4970@work-vm> (raw)
In-Reply-To: <20190228062803.GA7471@xz-x1>
* Peter Xu (peterx@redhat.com) wrote:
> On Wed, Feb 27, 2019 at 04:49:00PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Currently we cleanup the migration object as we exit main after the
> > main_loop finishes; however if there's a migration running things
> > get messy and we can end up with the migration thread still trying
> > to access freed structures.
> >
> > We now take a ref to the object around the migration thread itself,
> > so the act of dropping the ref during exit doesn't cause us to lose
> > the state until the thread quits.
> >
> > Cancelling the migration during migration also tries to get the thread
> > to quit.
> >
> > We do this a bit earlier; so hopefully migration gets out of the way
> > before all the devices etc are freed.
>
> So does it mean that even with the patch it's still possible the
> migration thread will be accessing device structs that have already
> been freed which can still crash QEMU?
Possibly yes; I'm not sure how to go to the next stage and stop that
case; the consensus seems to be we don't want to explicitly block
during the exit process, so doing a join on the migration thread doesn't
seem to be wanted.
Dave
> Thanks,
>
> --
> Peter Xu
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2019-02-28 11:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-27 16:49 [Qemu-devel] [PATCH] migration: Cleanup during exit Dr. David Alan Gilbert (git)
2019-02-27 20:32 ` Juan Quintela
2019-02-28 6:28 ` Peter Xu
2019-02-28 11:40 ` Dr. David Alan Gilbert [this message]
2019-02-28 12:01 ` Daniel P. Berrangé
2019-02-28 12:28 ` Dr. David Alan Gilbert
2019-03-01 3:27 ` Peter Xu
2019-03-01 10:11 ` Dr. David Alan Gilbert
2019-03-04 7:52 ` Peter Xu
2019-02-28 10:49 ` Alex Bennée
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