linux-kernel - Re: [tip:irq/urgent] genirq: Make legacy autoprobing work again

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Date:   Thu, 1 Feb 2018 12:35:33 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Meelis Roos <mroos@...ux.ee>, Ingo Molnar <mingo@...nel.org>,
        linux-tip-commits@...r.kernel.org,
        kbuild test robot <fengguang.wu@...el.com>
Subject: Re: [tip:irq/urgent] genirq: Make legacy autoprobing work again

On Thu, Feb 1, 2018 at 9:15 AM, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

>> +++ b/kernel/irq/chip.c
>> @@ -294,11 +294,11 @@ int irq_activate(struct irq_desc *desc)
>>         return 0;
>>  }
>>
>> -void irq_activate_and_startup(struct irq_desc *desc, bool resend)
>> +int irq_activate_and_startup(struct irq_desc *desc, bool resend)
>>  {
>>         if (WARN_ON(irq_activate(desc)))
>>                 return;
>
> As reported by 0day, this should return something.
>
> if CONFIG_IRQ_DOMAIN=n or CONFIG_IRQ_DOMAIN_HIERARCHY=n,
> irq_activate() will never return 1, and the code path can be eliminated.
>
> BTW, is gcc becoming too smart, and already eliminating code before it
> generates warnings for it? Recently I've seen some other cases where buggy
> code was not warned about, as it was considered not having any impact.
>

I've tried my collection of compiler versions, and they produce a warning here
on my box.

       Arnd