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Re: [PATCH 2/2] virtio_balloon: fix race between migration and ballooning

From "Michael S. Tsirkin" <mst@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 2/2] virtio_balloon: fix race between migration and ballooning
Date 2016-01-10 22:50 +0100
Message-ID <qPw26-1mc-7@gated-at.bofh.it> (permalink)
References <qKw2J-3Io-13@gated-at.bofh.it> <qKw2M-3Io-97@gated-at.bofh.it> <qM4lH-ob-7@gated-at.bofh.it> <qN1c6-4fx-9@gated-at.bofh.it>
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On Mon, Jan 04, 2016 at 09:27:47AM +0900, Minchan Kim wrote:
> > I think this will cause deadlocks.
> > 
> > pages_lock now nests within page lock, balloon_page_putback
> > nests them in the reverse order.
> 
> In balloon_page_dequeu, we used trylock so I don't think it's
> deadlock.

I went over this again and I don't see the issue anymore.
I think I was mistaken, so I dropped my patch and picked
up yours. Sorry about the noise.


> > 
> > Also, there's another issue there I think: after isolation page could
> > also get freed before we try to lock it.
> 
> If a page was isolated, the page shouldn't stay b_dev_info->pages
> list so balloon_page_dequeue cannot see the page.
> Am I missing something?

I mean without locks, as it is now. With either your or my patch in
place, it's fine.

-- 
MST

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Thread

Re: [PATCH 2/2] virtio_balloon: fix race between migration and  ballooning Minchan Kim <minchan@kernel.org> - 2016-01-04 01:30 +0100
  Re: [PATCH 2/2] virtio_balloon: fix race between migration and  ballooning "Michael S. Tsirkin" <mst@redhat.com> - 2016-01-10 22:50 +0100
    Re: [PATCH 2/2] virtio_balloon: fix race between migration and  ballooning Minchan Kim <minchan@kernel.org> - 2016-01-11 01:00 +0100

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