Re: [PATCH v3 8/8] ARM: make nr_irqs a constant

[Julien Grall <julien.grall@linaro.org>]

Hi Andre,

On 01/02/18 13:43, Andre Przywara wrote:
> On 30/01/18 14:36, Roger Pau Monné wrote:
>> On Wed, Jan 24, 2018 at 06:10:58PM +0000, Andre Przywara wrote:
>>> On ARM the maximum number of IRQs is a constant, but we share it being
>>> a variable to match x86. Since we are not supposed to alter it, let's
>>> mark it as "const" to avoid accidental change.
>>>
>>> Suggested-by: Julien Grall <julien.grall@linaro.org>
>>> Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
>>> ---
>>>   xen/arch/arm/irq.c        | 2 +-
>>>   xen/include/asm-arm/irq.h | 2 +-
>>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
>>> index 62103a20e3..d229cb6871 100644
>>> --- a/xen/arch/arm/irq.c
>>> +++ b/xen/arch/arm/irq.c
>>> @@ -27,7 +27,7 @@
>>>   #include <asm/gic.h>
>>>   #include <asm/vgic.h>
>>>   
>>> -unsigned int __read_mostly nr_irqs = NR_IRQS;
>>> +const unsigned int __read_mostly nr_irqs = NR_IRQS;
>>
>> Shouldn't you remove the __read_mostly attribute, so the symbol it's
>> placed at the .rodata section by the compiler?
> 
> Yes, makes sense, thanks for pointing this out!
> const ... __read_mostly sounds somewhat redundant.
> 
> It looks like the compiler does the right thing anyway, as I can't find
> nr_irqs in the ELF in any case. Both with and without __read_mostly it
> results into the very same binary, actually even without the const.

Really? I was expecting const data to be in the section.rodata. Are you 
suggesting this is landing in the section .data instead?

Cheers,

-- 
Julien Grall

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