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From: Sean Christopherson <seanjc@google.com>
To: Gavin Shan <gshan@redhat.com>
Cc: Florian Weimer <fweimer@redhat.com>,
	shan.gavin@gmail.com, kvm@vger.kernel.org, maz@kernel.org,
	linux-kernel@vger.kernel.org, andrew.jones@linux.dev,
	mathieu.desnoyers@efficios.com, yihyu@redhat.com,
	linux-kselftest@vger.kernel.org, pbonzini@redhat.com,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 2/2] KVM: selftests: Use getcpu() instead of sched_getcpu() in rseq_test
Date: Tue, 9 Aug 2022 20:53:36 +0000	[thread overview]
Message-ID: <YvLJUEOcxaZKW0y1@google.com> (raw)
In-Reply-To: <ea2ef1a2-0fd8-448b-d7ca-254603518823@redhat.com>

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".
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WARNING: multiple messages have this Message-ID (diff)
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
Date: Tue, 9 Aug 2022 20:53:36 +0000	[thread overview]
Message-ID: <YvLJUEOcxaZKW0y1@google.com> (raw)
In-Reply-To: <ea2ef1a2-0fd8-448b-d7ca-254603518823@redhat.com>

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".

  reply	other threads:[~2022-08-09 20:53 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-09  6:06 [PATCH 0/2] kvm/selftests: Two rseq_test fixes Gavin Shan
2022-08-09  6:06 ` Gavin Shan
2022-08-09  6:06 ` [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35 Gavin Shan
2022-08-09  6:06   ` Gavin Shan
2022-08-09  6:33   ` Florian Weimer
2022-08-09  6:33     ` Florian Weimer
2022-08-09  8:45     ` Gavin Shan
2022-08-09  8:45       ` Gavin Shan
2022-08-09  7:16       ` Florian Weimer
2022-08-09  7:16         ` Florian Weimer
2022-08-09  9:27         ` Gavin Shan
2022-08-09  9:27           ` Gavin Shan
2022-08-09 12:21           ` Mathieu Desnoyers
2022-08-09 12:21             ` Mathieu Desnoyers
2022-08-09 13:44             ` Mathieu Desnoyers
2022-08-09 13:44               ` Mathieu Desnoyers
2022-08-09 21:38               ` Sean Christopherson
2022-08-09 21:38                 ` Sean Christopherson
2022-08-10  0:37                 ` Gavin Shan
2022-08-10  0:37                   ` Gavin Shan
2022-08-10 12:29                   ` Mathieu Desnoyers
2022-08-10 12:29                     ` Mathieu Desnoyers
2022-08-10 12:35                     ` Paolo Bonzini
2022-08-10 12:35                       ` Paolo Bonzini
2022-08-10 12:13                 ` Mathieu Desnoyers
2022-08-10 12:13                   ` Mathieu Desnoyers
2022-08-10 23:52                   ` Gavin Shan
2022-08-10 23:52                     ` Gavin Shan
2022-08-10  9:14             ` Paolo Bonzini
2022-08-10  9:14               ` Paolo Bonzini
2022-08-10  9:59               ` Gavin Shan
2022-08-10  9:59                 ` Gavin Shan
2022-08-10 12:17               ` Mathieu Desnoyers
2022-08-10 12:17                 ` Mathieu Desnoyers
2022-08-10 12:19                 ` Paolo Bonzini
2022-08-10 12:19                   ` Paolo Bonzini
2022-08-10 23:34                   ` Gavin Shan
2022-08-10 23:34                     ` Gavin Shan
2022-08-09  6:06 ` [PATCH 2/2] KVM: selftests: Use getcpu() instead of sched_getcpu() in rseq_test Gavin Shan
2022-08-09  6:06   ` Gavin Shan
2022-08-09  6:35   ` Florian Weimer
2022-08-09  6:35     ` Florian Weimer
2022-08-09  7:17     ` Florian Weimer
2022-08-09  7:17       ` Florian Weimer
2022-08-09  8:46       ` Gavin Shan
2022-08-09  8:46         ` Gavin Shan
2022-08-09 20:53         ` Sean Christopherson [this message]
2022-08-09 20:53           ` Sean Christopherson
2022-08-10  0:45           ` Gavin Shan
2022-08-10  0:45             ` Gavin Shan

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