From: "Paul E. McKenney" <paulmck@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: "Andrii Nakryiko" <andrii.nakryiko@gmail.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
bpf <bpf@vger.kernel.org>
Subject: Re: Selftest failures related to kern_sync_rcu()
Date: Wed, 14 Apr 2021 11:19:34 -0700 [thread overview]
Message-ID: <20210414181934.GV4510@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <CAADnVQKyHb-j3-DSzF1wbzxYR39HdQiJVTVv1NkBS+9ZEeiEvg@mail.gmail.com>
On Wed, Apr 14, 2021 at 10:59:23AM -0700, Alexei Starovoitov wrote:
> On Wed, Apr 14, 2021 at 10:52 AM Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > > > > > if (num_online_cpus() > 1)
> > > > > > synchronize_rcu();
> >
> > In CONFIG_PREEMPT_NONE=y and CONFIG_PREEMPT_VOLUNTARY=y kernels, this
> > synchronize_rcu() will be a no-op anyway due to there only being the
> > one CPU. Or are these failures all happening in CONFIG_PREEMPT=y kernels,
> > and in tests where preemption could result in the observed failures?
> >
> > Could you please send your .config file, or at least the relevant portions
> > of it?
>
> That's my understanding as well. I assumed Toke has preempt=y.
> Otherwise the whole thing needs to be root caused properly.
Given that there is only a single CPU, I am still confused about what
the tests are expecting the membarrier() system call to do for them.
Thanx, Paul
next prev parent reply other threads:[~2021-04-14 18:19 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 19:34 Selftest failures related to kern_sync_rcu() Toke Høiland-Jørgensen
2021-04-13 3:38 ` Andrii Nakryiko
2021-04-13 8:50 ` Toke Høiland-Jørgensen
2021-04-13 21:43 ` Andrii Nakryiko
2021-04-14 15:54 ` Alexei Starovoitov
2021-04-14 17:52 ` Paul E. McKenney
2021-04-14 17:59 ` Alexei Starovoitov
2021-04-14 18:19 ` Paul E. McKenney [this message]
2021-04-14 18:39 ` Toke Høiland-Jørgensen
2021-04-14 18:41 ` Paul E. McKenney
2021-04-14 19:18 ` Toke Høiland-Jørgensen
2021-04-14 21:25 ` Paul E. McKenney
2021-04-14 22:13 ` Andrii Nakryiko
2021-04-14 22:27 ` Paul E. McKenney
2021-04-14 22:47 ` Toke Høiland-Jørgensen
2021-04-14 18:27 ` Toke Høiland-Jørgensen
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