linux-kernel - Re: [PATCH] powerpc: make irq_chip const, __initdata and _

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Message-ID: <87efr1lj4s.fsf@concordia.ellerman.id.au>
Date:   Wed, 20 Sep 2017 21:11:31 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Bhumika Goyal <bhumirks@...il.com>, benh@...nel.crashing.org,
        paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: make irq_chip const, __initdata and __initconst

Julia Lawall <julia.lawall@...6.fr> writes:

> On Wed, 20 Sep 2017, Michael Ellerman wrote:
>
>> Bhumika Goyal <bhumirks@...il.com> writes:
>>
>> > Make ehv_pic_irq_chip, mpic_ipi_chip and mpic_tm_chip const as they are
>> > used only as a copy operation. This usage is during init, so make them
>> > __initconst too.
>> > Make mpic_ipi_chip __initdata as it is only modified during the init
>> > phase and there is no reference of it anywhere after init.
>>
>> The change log doesn't seem to match the code.
>>
>> It's mpic_tm_chip which you marked __initdata, and that looks wrong, as
>> we keep a pointer to it here:
>>
>> 	mpic->hc_tm = mpic_tm_chip;
>
> This looks like a memory copy.

Yes you're right.

That's pretty horrible given the size of struct irq_chip, but it's not a
bug in this patch.

There are 5 struct irq_chip's embedded in struct mpic, it must be
enormous!

cheers