Re: Is module refcounting racy?

From: Linus Torvalds
Date: Thu Apr 01 2010 - 12:01:10 EST

On Thu, 1 Apr 2010, Nick Piggin wrote:
> I think it can be done racelessly with my patch, which is not really too
> much overhead. I think if this is considered too much, then we should
> either fix code and preferably de-export and remove module_refcount from
> drivers, or remove module removal completely.

I doubt your patch matters too much, but I like it conceptually and it
seems to be a nice basis for perhaps doing something clever in the long

[ ie avoiding the stop_machine and instead perhaps doing some optimistic
thing like "see if we seem to be unused right now, then unregister us,
and see - after unregistering - that the usage counts haven't increased,
and re-register if they have. ]

So I'd like to apply it as a "good improvement, even if module unloading
which is the only thing that _should_ care deeply should already be under

But I'd like an ack or two first.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at