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

[Lukas Straub]

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.

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  
>

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