Re: [PATCH] irq: Remove unnecessary warning with affinity_hint

Ingo Molnar
2015-04-08T06:28:55Z

* Seiichi Ikarashi <s.ikarashi@jp.fujitsu.com> wrote:

> Hi,
>
> If you turn off a PCI device whose driver has set affinity_hint,
> you will get warning message which does _not_ explain the reason
> why it appeared from the user's point of view.
>
> # echo 0 > /sys/bus/pci/slots/65/power
>
> Apr 28 20:29:39 localhost kernel: ------------[ cut here ]------------
> Apr 28 20:29:39 localhost kernel: WARNING: at kernel/irq/manage.c:1002 __free_irq+0x22d/0x250() (Tainted: P --------------- )
> (snip)
>
> Users will misunderstand some problem has happened
> even though he or she succeeded to turn off the device.
> I suppose this warning was originally for a debug purpose
> for driver developers and has incidentally been left.
>
> Just remove the warning is good and enough.
>
> Signed-off-by: Seiichi Ikarashi <s.ikarashi@jp.fujitsu.com>
>
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1335,7 +1335,7 @@ static struct irqaction *__free_irq(unsi
>
> #ifdef CONFIG_SMP
> /* make sure affinity_hint is cleaned up */
> - if (WARN_ON_ONCE(desc->affinity_hint))
> + if (desc->affinity_hint)
> desc->affinity_hint = NULL;

Well, drivers that are using irq_set_affinity_hint() are expected to
call:

irq_set_affinity_hint(irq, NULL);

to clear the affinity mask, before releasing the irq. This warning
flags drivers that forgot to do that and which might thus leak a
dynamically allocated CPU mask (and/or other resources).

Feel free to turn the warning message into a more informative WARN()
that will blame the driver that triggered it, if the stack dump into
the driver wasn't a clue enough ...

Thanks,

Ingo