Messages in this thread | | | Date | Thu, 9 Apr 2015 16:49:38 +0200 | From | Ingo Molnar <> | Subject | Re: [tip:irq/core] genirq: MSI: Fix freeing of unallocated MSI |
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* Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 9 Apr 2015, Marc Zyngier wrote: > > On Thu, 9 Apr 2015 13:00:23 +0100 > > Ingo Molnar <mingo@kernel.org> wrote: > > > > > > Hm, so this appears to be the first time that 'irq == 0' assumptions > > > are getting into the genirq core. Is NO_IRQ dead? I realize that the > > > MSI code uses '!irq' as a flag, but still, quite a few architectures > > > define NO_IRQ so it appears to matter to them. > > > > NO_IRQ strikes back, everybody takes cover! ;-) > > > > More seriously, this seems to be two schools of thoughts on that > > one. The irqdomain subsystem seems to treat 'irq == 0' as the > > indication that 'this is not a valid IRQ', and so does MSI (as you > > noticed). Given that this code deals with MSI in conjunction with > > irqdomains, it felt natural to adopt the same convention. > > > > Also, not all the architecture are defining NO_IRQ, and it only > > seems to be used in code that is doesn't look portable across > > architectures. Either these architecture don't care about MSI, or > > they are happy enough to consider that virtual interrupt 0 is > > invalid in the MSI case. > > > > So I'm a bit lost on that one. I sincerely thought NO_IRQ was > > being retired (https://lwn.net/Articles/470820/). Should we > > introduce a NO_MSI_IRQ (set to zero) to take care of this case? > > Nah, that'd be overkill. irq 0 is invalid for MSI in any case so we > really should stick with that convention.
That makes sense - should we more aggressively eliminate NO_IRQ perhaps?
I'm seeing stuff like:
irq = irq_of_parse_and_map(np, 0); if (!handle || (irq == NO_IRQ)) {
in fairly recent (2-4 years old) code, and irq_of_parse_and_map() is used in 300+ places.
Thanks,
Ingo
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