From: Qian Cai <cai@redhat.com>
To: Will Deacon <will@kernel.org>, "Paul E. McKenney" <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
catalin.marinas@arm.com, kernel-team@android.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64/smp: Move rcu_cpu_starting() earlier
Date: Thu, 05 Nov 2020 18:02:49 -0500 [thread overview]
Message-ID: <3b4c324abdabd12d7bd5346c18411e667afe6a55.camel@redhat.com> (raw)
In-Reply-To: <20201105222242.GA8842@willie-the-truck>
On Thu, 2020-11-05 at 22:22 +0000, Will Deacon wrote:
> On Fri, Oct 30, 2020 at 04:33:25PM +0000, Will Deacon wrote:
> > On Wed, 28 Oct 2020 14:26:14 -0400, Qian Cai wrote:
> > > The call to rcu_cpu_starting() in secondary_start_kernel() is not early
> > > enough in the CPU-hotplug onlining process, which results in lockdep
> > > splats as follows:
> > >
> > > WARNING: suspicious RCU usage
> > > -----------------------------
> > > kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!!
> > >
> > > [...]
> >
> > Applied to arm64 (for-next/fixes), thanks!
> >
> > [1/1] arm64/smp: Move rcu_cpu_starting() earlier
> > https://git.kernel.org/arm64/c/ce3d31ad3cac
>
> Hmm, this patch has caused a regression in the case that we fail to
> online a CPU because it has incompatible CPU features and so we park it
> in cpu_die_early(). We now get an endless spew of RCU stalls because the
> core will never come online, but is being tracked by RCU. So I'm tempted
> to revert this and live with the lockdep warning while we figure out a
> proper fix.
>
> What's the correct say to undo rcu_cpu_starting(), given that we cannot
> invoke the full hotplug machinery here? Is it correct to call
> rcutree_dying_cpu() on the bad CPU and then rcutree_dead_cpu() from the
> CPU doing cpu_up(), or should we do something else?
It looks to me that rcu_report_dead() does the opposite of rcu_cpu_starting(),
so lift rcu_report_dead() out of CONFIG_HOTPLUG_CPU and use it there to rewind,
Paul?
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-11-05 23:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-28 18:26 [PATCH] arm64/smp: Move rcu_cpu_starting() earlier Qian Cai
2020-10-28 21:00 ` Paul E. McKenney
2020-10-29 9:10 ` Will Deacon
2020-10-29 13:17 ` Qian Cai
2020-10-30 8:15 ` Will Deacon
2020-10-29 14:09 ` Paul E. McKenney
2020-10-30 16:33 ` Will Deacon
2020-11-05 22:22 ` Will Deacon
2020-11-05 23:02 ` Qian Cai [this message]
2020-11-05 23:28 ` Paul E. McKenney
2020-11-06 2:15 ` Qian Cai
2020-11-06 4:07 ` Paul E. McKenney
2020-11-06 10:37 ` Will Deacon
2020-11-06 12:48 ` Qian Cai
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3b4c324abdabd12d7bd5346c18411e667afe6a55.camel@redhat.com \
--to=cai@redhat.com \
--cc=catalin.marinas@arm.com \
--cc=kernel-team@android.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox