linux-kernel - Re: [PATCH v2 1/2] arm64/arch_timer: include <linux/percpu.h>

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Date: Fri, 03 May 2024 09:44:14 +0000
From: Puranjay Mohan <puranjay@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Sumit Garg
 <sumit.garg@...aro.org>, Stephen Boyd <swboyd@...omium.org>, Douglas
 Anderson <dianders@...omium.org>, "Peter Zijlstra (Intel)"
 <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Mark Rutland
 <mark.rutland@....com>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v2 1/2] arm64/arch_timer: include <linux/percpu.h>

Anshuman Khandual <anshuman.khandual@....com> writes:

> On 5/2/24 18:04, Puranjay Mohan wrote:
>> arch_timer.h includes linux/smp.h to use DEFINE_PER_CPU() and it works
>> because smp.h includes percpu.h. The next commit will remove percpu.h
>> from smp.h and it will break this usage.
>> 
>> Explicitly include percpu.h and remove smp.h
>
> But this particular change does not seem to be necessary for changing
> raw_smp_processor_id() as current_thread_info()->cpu being done in the
> later patch ? You might still leave header <asm/percpu.h> inclusion in
> arch/arm64/include/asm/smp.h while dropping the per cpu cpu_number ?

commit 57c82954e77f ("arm64: make cpu number a percpu variable")
created this percpu variable and included <asm/percpu.h> in <asm/smp.h>

Now we are removing the percpu variable cpu_number from smp.h, so there
is no need to keep percpu.h in smp.h

I feel users of DECLARE_PER_CPU_[...], etc. should include percpu.h and
not smp.h as it makes reading the code more easier and can thwart build
issues in the future, when headers are changed. 

Thanks,
Puranjay