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;
Date:   Tue, 9 Aug 2022 20:53:36 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Gavin Shan <gshan@redhat.com>
Cc:     Florian Weimer <fweimer@redhat.com>, 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,
        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
Message-ID: <YvLJUEOcxaZKW0y1@google.com>
References: <20220809060627.115847-1-gshan@redhat.com>
 <20220809060627.115847-3-gshan@redhat.com>
 <87y1vxncv1.fsf@oldenburg.str.redhat.com>
 <87mtcdnaxe.fsf@oldenburg.str.redhat.com>
 <ea2ef1a2-0fd8-448b-d7ca-254603518823@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <ea2ef1a2-0fd8-448b-d7ca-254603518823@redhat.com>
Precedence: bulk

On Tue, Aug 09, 2022, Gavin Shan wrote:
> 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 :)

+1, and definitely add a comment to prevent future "cleanup".