Received-SPF: pass (google.com: domain of linux-kernel+bounces-18751-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Date: Sat, 6 Jan 2024 16:49:49 -0800
From: "Paul E. McKenney" <paulmck@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Prototype patch to avoid TREE07 rcu_torture_writer() stalls
Message-ID: <127b057c-446e-4b3f-bb04-d1c4efdded0f@paulmck-laptop>
Reply-To: paulmck@kernel.org
References: <a40344c8-a260-41f3-bd7a-6a63d8660489@paulmck-laptop>
 <ZZiIQvu+2CGufvOL@lothringen>
 <3da2e014-ed54-4b2a-9fde-99d6eef3e897@paulmck-laptop>
 <8c135e1a-5f66-42ae-9749-71a65f86dcbf@paulmck-laptop>
 <ZZnV0xt9ZhAu-vUh@localhost.localdomain>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <ZZnV0xt9ZhAu-vUh@localhost.localdomain>

On Sat, Jan 06, 2024 at 11:36:03PM +0100, Frederic Weisbecker wrote:
> Le Sat, Jan 06, 2024 at 06:55:14AM -0800, Paul E. McKenney a ?crit :
> > > Is this related?
> > > 
> > > But then the system picks itself up, dusts itself off, and goes along
> > > as if nothing had happened.
> > > 
> > > Maybe a long-running IRQ, NMI, or SMI?
> > 
> > Or, based on a recent bug chase of another type, high contention on
> > an IRQ-disabled spinlock?
> 
> Before checking the guest's dmesg, I should probably have checked the host's.
> It seems to report some softlockups, perhaps due to too many instances
> in parallel where memory is not that generous.

That would do it!

> Let me try to run as much time (250 hours) but with fewer instances in
> parallel.

I just today saw an extended stall on one instance of TREE03, also
RCU grace-period kthread starvation.  But this was in -next, which
is also having other yet-as-unanalyzed issues.

							Thanx, Paul