[Qemu-devel] Re: [PATCH 3/5] iohandlers: Allow each iohandler to be enabled/disabled individually

[Gerd Hoffmann]

On 01/13/11 15:00, Amit Shah wrote:
> On (Thu) Jan 13 2011 [14:55:25], Gerd Hoffmann wrote:
> > On 01/13/11 14:00, Amit Shah wrote:
> > >   {
> > > -    return assign_fd_handlers(fd, fd_read_poll, fd_read, fd_write, opaque);
> > > +    assign_fd_handlers(fd, fd_read_poll, fd_read, fd_write, opaque);
> > > +    set_read_poll_fd_action(fd, true);
> > > +    set_read_fd_action(fd, true);
> > > +    set_write_fd_action(fd, true);
> > > +    return 0;
> > >   }
> >
> > I'd suggest to move the *action calls into assign_fd_handlers() so
> > the handlers default to being enabled in all cases.  This should
> > match what most users need and thus minimize the number of *_action
> > calls needed.
>
> What may happen with that is the fd may get select()-ed for an operation
> that it didn't want to be put on the queue for.

I can't see such a race window given that most qemu code runs serialized 
anyway.  If you call assign_fd_handlers() + set_write_fd_action(false) 
in sequence I can't see how a select call can happen inbetween ...

cheers,
  Gerd