Re: [Qemu-devel] [RFC PATCH 6/9] blkdebug: Implement .cancel_async

[Fam Zheng]

On Thu, 08/21 17:52, Stefan Hajnoczi wrote:
> On Thu, Aug 21, 2014 at 07:56:53PM +0800, Fam Zheng wrote:
> > @@ -446,12 +439,25 @@ static void error_callback_bh(void *opaque)
> >      qemu_aio_release(acb);
> >  }
> >  
> > +static void blkdebug_aio_cancel_async(BlockDriverAIOCB *blockacb)
> > +{
> > +    BlkdebugAIOCB *acb = container_of(blockacb, BlkdebugAIOCB, common);
> > +    blockacb->cb(blockacb->opaque, -ECANCELED);
> > +    qemu_aio_release(acb);
> > +}
> > +
> >  static void blkdebug_aio_cancel(BlockDriverAIOCB *blockacb)
> >  {
> >      BlkdebugAIOCB *acb = container_of(blockacb, BlkdebugAIOCB, common);
> >      qemu_aio_release(acb);
> >  }
> 
> Both blkdebug_aio_cancel() and blkdebug_aio_cancel_async() look
> incorrect.  It is not safe to release acb because the
> error_callback_bh() BH may still be scheduled.
> 
> I guess we don't hit this problem because the error injection happens
> within the same event loop iteration.  In practice no one ever calls
> blkdebug_aio_cancel()?
> 

I'll drop this patch and send a separate fix for blkdebug_aio_cancel.

Fam