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

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Date:   Tue, 09 Aug 2022 09:17:01 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Gavin Shan <gshan@...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

* 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