linux-kernel - Re: [PATCH 2/2] KVM: selftests: Use getcpu() instead of sched_getcpu() in rseq

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Date:   Tue, 9 Aug 2022 18:46:39 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, maz@...nel.org, oliver.upton@...ux.dev,
        andrew.jones@...ux.dev, seanjc@...gle.com,
        mathieu.desnoyers@...icios.com, yihyu@...hat.com,
        shan.gavin@...il.com
Subject: Re: [PATCH 2/2] KVM: selftests: Use getcpu() instead of
 sched_getcpu() in rseq_test

On 8/9/22 5:17 PM, Florian Weimer wrote:
> * Florian Weimer:
> 
>> * Gavin Shan:
>>
>>> sched_getcpu() is glibc dependent and it can simply return the CPU
>>> ID from the registered rseq information, as Florian Weimer pointed.
>>> In this case, it's pointless to compare the return value from
>>> sched_getcpu() and that fetched from the registered rseq information.
>>>
>>> Fix the issue by replacing sched_getcpu() with getcpu(), as Florian
>>> suggested. The comments are modified accordingly.
>>
>> Note that getcpu was added in glibc 2.29, so perhaps you need to perform
>> a direct system call?
> 
> One more thing: syscall(__NR_getcpu) also has the advantage that it
> wouldn't have to be changed again if node IDs become available via rseq
> and getcpu is implemented using that.
> 
> Thanks,
> Florian
> 

Thanks, Florian. It makes sense to me to use syscall(__NR_getcpu) in
next revision. Thanks for your quick review :)

I would hold for one or two days to post v2, to see if others have
more comments.

Thanks,
Gavin