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Date: Wed, 20 Jul 2011 13:34:50 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
Message-ID: <20110720163450.GA17333@amt.cnet>
References: <20110719115511.609C553E5@gandalf.tls.msk.ru>
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Subject: Re: [Qemu-devel] [PATCH] do not call monitor_resume() from
 migrate_fd_put_buffer() error path
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Michael Tokarev <mjt@tls.msk.ru>, qemu-devel@nongnu.org

On Tue, Jul 19, 2011 at 11:48:22PM +0200, Jan Kiszka wrote:
> On 2011-07-19 13:46, Michael Tokarev wrote:
> > If we do, it results in double monitor_resume() (second being called
> > from migrate_fd_cleanup() anyway) and monitor suspend count becoming
> > negative.
> > 
> > Cc'ing people from `git blame' list for the lines in question: the
> > change fixes the problem but I'm not sure what the original intention
> > of this code was in this place.  Unfortunately noone replied to two
> > my attempts to raise this issue.
> > 
> > Signed-Off-By: Michael Tokarev <mjt@tls.msk.ru>
> > ---
> >  migration.c |    3 ---
> >  1 files changed, 0 insertions(+), 3 deletions(-)
> > 
> > diff --git a/migration.c b/migration.c
> > index af3a1f2..115588c 100644
> > --- a/migration.c
> > +++ b/migration.c
> > @@ -330,9 +330,6 @@ ssize_t migrate_fd_put_buffer(void *opaque, const void *data, size_t size)
> >      if (ret == -EAGAIN) {
> >          qemu_set_fd_handler2(s->fd, NULL, NULL, migrate_fd_put_notify, s);
> >      } else if (ret < 0) {
> > -        if (s->mon) {
> > -            monitor_resume(s->mon);
> > -        }
> >          s->state = MIG_STATE_ERROR;
> >          notifier_list_notify(&migration_state_notifiers);
> >      }
> 
> Looks reasonable to me, but Marcelo should comment on this, specifically
> which scenario once required the resume.
> 
> Jan

If the monitor was suspended (migrate without -d), then this path must
resume. Should record that somewhere and check here.