Re: [RFC PATCH] notifier: Return non-null when callback already registered

[Borislav Petkov]

On Fri, May 21, 2021 at 01:11:42PM +0200, Peter Zijlstra wrote:
> > @@ -25,7 +25,7 @@ static int notifier_chain_register(struct notifier_block **nl,
> >  	while ((*nl) != NULL) {
> >  		if (unlikely((*nl) == n)) {
> >  			WARN(1, "double register detected");
> 
> That should give a big clue^

Yah, the big cluebat... Was wondering whether to remove it, actually.
But then I'd need to audit all users whether they handle retval
properly. Sounds like a kernelnewbies project to me...

> > -			return 0;
> > +			return 1;
> 
> How about -EBUSY here?

Yah, anthing but 0.

But if we're gonna return -E things, -EEXIST looks like an even better
fit to me...

Thx.

-- 
Regards/Gruss,
    Boris.

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