On 2015-04-08 16:39, Ingo Molnar wrote: > > * Seiichi Ikarashi <s.ikara...@jp.fujitsu.com> wrote: > >> Hi, >> >> On 2015-04-08 15:28, Ingo Molnar wrote: >>> >>> * Seiichi Ikarashi <s.ikara...@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.ikara...@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). >> >> Calling irq_set_affinity_hint(irq, NULL) does not guarantee that the >> driver does not forget to deallocate a dynamically allocated CPU >> mask and/or other resources. [...] > > I said 'might leak', not 'guaranteed to leak'.
Yes, I know. I wrote it because I was not sure about the primary purpose of showing the warning message. > > Calling irq_set_affinity_hint(irq, NULL) is the way this kernel API is > specified to be used. Forgetting to do it is a kernel driver bug and > triggers a warning message from the kernel's IRQ subsystem. > >> [...] But if calling it with NULL 2nd-arg before releasing the irq >> is a virtual rule of using irq_set_affinity_hint() interface, I >> understand it. >> >>> 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 ... >> >> Still, I do not know leaving the warning message is effective to >> prevent drivers from potentially leaking resource... considering a >> kind of cost-effectivenss. Business users (not developers) hate such >> kind of messages for developers. > > it's a warning message pointing out a kernel bug: that > irq_set_affinity_hint(irq, NULL) was not called properly. > > Messages pointing out kernel bugs should be fixed, not hidden. OK, the conclusion is that a kernel bug on using irq_set_affinity_hint(). Thanks, Ingo. Seiichi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
