Re: Fault tolerance/bad patch, [was Re: [PATCH 29/30] [PATCH] PCI Hotplug: fake NULL pointer dereferences in IBM Hot Plug Controller Driver]

[Eric Sesterhenn / Snakebyte <snakebyte@gmx.de>]

* Alan Cox (alan@lxorguk.ukuu.org.uk) wrote:
> Ar Gwe, 2006-06-23 am 10:04 -0500, ysgrifennodd Linas Vepstas:
> > If someone in the future changes the hotplug core so that it 
> > sometimes returns a null value, this code will potentially crash
> > and/or do other bad things (corrupt, invalid state, etc.)
> > This means that this routine will no longer be "robust" in the face of
> > changes in other parts of the kernel. 
> 
> "Potentially".
> 
> But if you replaced it with
> 
> BUG_ON(value == NULL);
> 
> you'd both clean up the if and improve the reliability even more
> 
> > I can hear the objections:
> > -- Performance. B.S. This routine is not performance critical, it will
> >    get called once a week, once a month or less often; a few extra
> >    cycles are utterly irrelevant.
> 
> (and half the time gcc eliminates the test itself)
> 

I guess the BUG_ON makes more sense than keeping the
check, the reason coverity stumbled across this,
is the debug("get_attention_status - Exit rc[%d] value[%x]\n", rc,
*value); call some lines later, which uses the pointer.
If we just keep the check, we should also put one
around the debug statement

Greetings, Eric