Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Florian Weimer <fweimer@redhat.com>
To:     Gavin Shan <gshan@redhat.com>
Cc:     kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
        pbonzini@redhat.com, maz@kernel.org, oliver.upton@linux.dev,
        andrew.jones@linux.dev, seanjc@google.com,
        mathieu.desnoyers@efficios.com, yihyu@redhat.com,
        shan.gavin@gmail.com
Subject: Re: [PATCH 2/2] KVM: selftests: Use getcpu() instead of
 sched_getcpu() in rseq_test
References: <20220809060627.115847-1-gshan@redhat.com>
        <20220809060627.115847-3-gshan@redhat.com>
        <87y1vxncv1.fsf@oldenburg.str.redhat.com>
Date:   Tue, 09 Aug 2022 09:17:01 +0200
In-Reply-To: <87y1vxncv1.fsf@oldenburg.str.redhat.com> (Florian Weimer's
        message of "Tue, 09 Aug 2022 08:35:14 +0200")
Message-ID: <87mtcdnaxe.fsf@oldenburg.str.redhat.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

* 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