Re: [PATCH v4 6/6] net/colo-compare.c: Correct ordering in complete and finalize

[Lukas Straub]

On Thu, 7 May 2020 13:26:11 +0000
"Zhang, Chen" <address@hidden> wrote:

> > -----Original Message-----
> > From: Lukas Straub <address@hidden>
> > Sent: Monday, May 4, 2020 6:28 PM
> > To: qemu-devel <address@hidden>
> > Cc: Zhang, Chen <address@hidden>; Li Zhijian
> > <address@hidden>; Jason Wang <address@hidden>; Marc-
> > André Lureau <address@hidden>; Paolo Bonzini
> > <address@hidden>
> > Subject: [PATCH v4 6/6] net/colo-compare.c: Correct ordering in complete
> > and finalize
> > 
> > In colo_compare_complete, insert CompareState into net_compares only
> > after everything has been initialized.
> > In colo_compare_finalize, remove CompareState from net_compares before
> > anything is deinitialized.  
> 
> S/deinitialized/finalized
> 
> It looks no dependences on each step on initialization and finalization.
> Do you means we just need add/remove each colo-compare module at last in 
> logic?

Yes. While I didn't see any crashes here, there is the possibility that if 
colo-compare is removed during checkpoint, the destroyed event_bh is called 
from colo_notify_compares_event. Same with colo_compare_complete (very 
unlikely) if colo-compare is created while colo is running, 
colo_notify_compares_event may call the uninitialized event_bh.

Regards,
Lukas Straub

> Or current code have some issue?
> 
> Thanks
> Zhang Chen
> 
> > 
> > Signed-off-by: Lukas Straub <address@hidden>
> > ---
> >  net/colo-compare.c | 45 +++++++++++++++++++++++----------------------
> >  1 file changed, 23 insertions(+), 22 deletions(-)
> > 
> > diff --git a/net/colo-compare.c b/net/colo-compare.c index
> > c7572d75e9..6f80bcece6 100644
> > --- a/net/colo-compare.c
> > +++ b/net/colo-compare.c
> > @@ -1283,15 +1283,6 @@ static void
> > colo_compare_complete(UserCreatable *uc, Error **errp)
> >                             s->vnet_hdr);
> >      }
> > 
> > -    qemu_mutex_lock(&colo_compare_mutex);
> > -    if (!colo_compare_active) {
> > -        qemu_mutex_init(&event_mtx);
> > -        qemu_cond_init(&event_complete_cond);
> > -        colo_compare_active = true;
> > -    }
> > -    QTAILQ_INSERT_TAIL(&net_compares, s, next);
> > -    qemu_mutex_unlock(&colo_compare_mutex);
> > -
> >      s->out_sendco.s = s;
> >      s->out_sendco.chr = &s->chr_out;
> >      s->out_sendco.notify_remote_frame = false; @@ -1312,6 +1303,16 @@
> > static void colo_compare_complete(UserCreatable *uc, Error **errp)
> >                                                        connection_destroy);
> > 
> >      colo_compare_iothread(s);
> > +
> > +    qemu_mutex_lock(&colo_compare_mutex);
> > +    if (!colo_compare_active) {
> > +        qemu_mutex_init(&event_mtx);
> > +        qemu_cond_init(&event_complete_cond);
> > +        colo_compare_active = true;
> > +    }
> > +    QTAILQ_INSERT_TAIL(&net_compares, s, next);
> > +    qemu_mutex_unlock(&colo_compare_mutex);
> > +
> >      return;
> >  }
> > 
> > @@ -1384,19 +1385,6 @@ static void colo_compare_finalize(Object *obj)
> >      CompareState *s = COLO_COMPARE(obj);
> >      CompareState *tmp = NULL;
> > 
> > -    qemu_chr_fe_deinit(&s->chr_pri_in, false);
> > -    qemu_chr_fe_deinit(&s->chr_sec_in, false);
> > -    qemu_chr_fe_deinit(&s->chr_out, false);
> > -    if (s->notify_dev) {
> > -        qemu_chr_fe_deinit(&s->chr_notify_dev, false);
> > -    }
> > -
> > -    if (s->iothread) {
> > -        colo_compare_timer_del(s);
> > -    }
> > -
> > -    qemu_bh_delete(s->event_bh);
> > -
> >      qemu_mutex_lock(&colo_compare_mutex);
> >      QTAILQ_FOREACH(tmp, &net_compares, next) {
> >          if (tmp == s) {
> > @@ -1411,6 +1399,19 @@ static void colo_compare_finalize(Object *obj)
> >      }
> >      qemu_mutex_unlock(&colo_compare_mutex);
> > 
> > +    qemu_chr_fe_deinit(&s->chr_pri_in, false);
> > +    qemu_chr_fe_deinit(&s->chr_sec_in, false);
> > +    qemu_chr_fe_deinit(&s->chr_out, false);
> > +    if (s->notify_dev) {
> > +        qemu_chr_fe_deinit(&s->chr_notify_dev, false);
> > +    }
> > +
> > +    if (s->iothread) {
> > +        colo_compare_timer_del(s);
> > +    }
> > +
> > +    qemu_bh_delete(s->event_bh);
> > +
> >      AioContext *ctx = iothread_get_aio_context(s->iothread);
> >      aio_context_acquire(ctx);
> >      AIO_WAIT_WHILE(ctx, !s->out_sendco.done);
> > --
> > 2.20.1

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