Re: [PATCH 1/3] net/colo-compare.c: Create event_bh with the right AioContext

[Lukas Straub <lukasstraub2@web.de>]

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On Wed, 22 Apr 2020 08:29:39 +0000
"Zhang, Chen" <chen.zhang@intel.com> wrote:

> > -----Original Message-----
> > From: Lukas Straub <lukasstraub2@web.de>
> > Sent: Thursday, April 9, 2020 2:34 AM
> > To: qemu-devel <qemu-devel@nongnu.org>
> > Cc: Zhang, Chen <chen.zhang@intel.com>; Li Zhijian
> > <lizhijian@cn.fujitsu.com>; Jason Wang <jasowang@redhat.com>; Marc-
> > André Lureau <marcandre.lureau@redhat.com>; Paolo Bonzini
> > <pbonzini@redhat.com>
> > Subject: [PATCH 1/3] net/colo-compare.c: Create event_bh with the right
> > AioContext
> > 
> > qemu_bh_new will set the bh to be executed in the main loop. This causes
> > problems as colo_compare_handle_event assumes that it has exclusive
> > access the queues, which are also accessed in the iothread. It also assumes
> > that it runs in a different thread than the caller and takes the appropriate
> > locks.
> > 
> > Create the bh with the AioContext of the iothread to fulfill these
> > assumptions.
> >   
> 
> Looks good for me, I assume it will increase performance. Do you have related data?

No, this fixes several crashes because the queues where accessed concurrently from
multiple threads. Sorry for my bad wording.

Regards,
Lukas Straub

> Thanks
> Zhang Chen
> 
> > Signed-off-by: Lukas Straub <lukasstraub2@web.de>
> > ---
> >  net/colo-compare.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/colo-compare.c b/net/colo-compare.c index
> > 10c0239f9d..1de4220fe2 100644
> > --- a/net/colo-compare.c
> > +++ b/net/colo-compare.c
> > @@ -890,6 +890,7 @@ static void colo_compare_handle_event(void
> > *opaque)
> > 
> >  static void colo_compare_iothread(CompareState *s)  {
> > +    AioContext *ctx = iothread_get_aio_context(s->iothread);
> >      object_ref(OBJECT(s->iothread));
> >      s->worker_context = iothread_get_g_main_context(s->iothread);
> > 
> > @@ -906,7 +907,7 @@ static void colo_compare_iothread(CompareState *s)
> >      }
> > 
> >      colo_compare_timer_init(s);
> > -    s->event_bh = qemu_bh_new(colo_compare_handle_event, s);
> > +    s->event_bh = aio_bh_new(ctx, colo_compare_handle_event, s);
> >  }
> > 
> >  static char *compare_get_pri_indev(Object *obj, Error **errp)
> > --
> > 2.20.1  
> 


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