Re: [KVM PATCH v2 2/2] kvm: use POLLHUP to close an irqfd instead of an explicit ioctl

Michael S. Tsirkin
2009-06-15T12:55:00Z

On Mon, Jun 15, 2009 at 08:08:18AM -0400, Gregory Haskins wrote:
> >> @@ -123,6 +124,7 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int
> >> sync, void
> >> *key)
> >>
> >> cleanup_srcu_struct(&irqfd->srcu);
> >> kfree(irqfd);
> >> + module_put(THIS_MODULE);
> >> }
> >>
> >> return 0;
> >>
> >
> > module_put(THIS_MODULE) is always a bug unless you know that someone has
> > a reference to the current module: the module could go away between this
> > call and returning from function.
> >
>
> Hmm. I understand what you are saying conceptually (i.e. the .text
> could get yanked before we hit the next line of code, in this case the
> "return 0"). However, holding a reference when you _know_ someone else
> holds a reference to me says that one of the references is redundant.
> In addition, there is certainly plenty of precedence for
> module_put(THIS_MODULE) all throughout the kernel (including
> module_put_and_exit()). Are those broken as well?

Maybe not, but I don't know why. It works fine as long as you don't
unload any modules though :) Rusty, could you enlighten us please?

--
MST