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

[Zhang, Chen]

> -----Original Message-----
> From: Lukas Straub <address@hidden>
> Sent: Wednesday, April 22, 2020 4:43 PM
> To: Zhang, Chen <address@hidden>
> Cc: qemu-devel <address@hidden>; Li Zhijian
> <address@hidden>; Jason Wang <address@hidden>; Marc-
> André Lureau <address@hidden>; Paolo Bonzini
> <address@hidden>
> Subject: Re: [PATCH 1/3] net/colo-compare.c: Create event_bh with the right
> AioContext
> 
> On Wed, 22 Apr 2020 08:29:39 +0000
> "Zhang, Chen" <address@hidden> wrote:
> 
> > > -----Original Message-----
> > > From: Lukas Straub <address@hidden>
> > > Sent: Thursday, April 9, 2020 2:34 AM
> > > 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 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.

Can you describe some details about the crash? Step by step?
Maybe I can re-produce and test it for this patch.

Thanks
Zhang Chen

> 
> Regards,
> Lukas Straub
> 
> > Thanks
> > Zhang Chen
> >
> > > Signed-off-by: Lukas Straub <address@hidden>
> > > ---
> > >  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
> >