linux-kernel - Re: [PATCH v2 05/12] rcutorture: Add tests for SRCU up/down reader primitives

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Message-ID: <1d60ee60-2924-433d-a9b7-726f82f0e546@paulmck-laptop>
Date: Tue, 15 Apr 2025 14:15:15 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Joel Fernandes <joelagnelf@...dia.com>
Cc: rcu@...r.kernel.org, linux-kernel@...r.kernel.org, kernel-team@...a.com,
	rostedt@...dmis.org
Subject: Re: [PATCH v2 05/12] rcutorture: Add tests for SRCU up/down reader
 primitives

On Tue, Apr 15, 2025 at 10:59:36AM -0700, Paul E. McKenney wrote:
> On Tue, Apr 15, 2025 at 01:16:15PM -0400, Joel Fernandes wrote:
> > 
> > 
> > On 3/31/2025 5:03 PM, Paul E. McKenney wrote:
> > > This commit adds a new rcutorture.n_up_down kernel boot parameter
> > > that specifies the number of outstanding SRCU up/down readers, which
> > > begin in kthread context and end in an hrtimer handler.  There is a new
> > > kthread ("rcu_torture_updown") that scans an per-reader array looking
> > > for elements whose readers have ended.  This kthread sleeps between one
> > > and two milliseconds between consecutive scans.
> > > 
> > > [ paulmck: Apply kernel test robot feedback. ]
> > > [ paulmck: Apply Z qiang feedback. ]
> > > 
> > > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > 
> > For completeness, posting our discussion for the archives, an issue exists in
> > this patch causing the following errors on an ARM64 machine with 288 CPUs:
> > 
> > When running SRCU-P test, we intermittently see:
> > 
> > [ 9500.806108] ??? Writer stall state RTWS_SYNC(21) g18446744073709551218 f0x0
> > ->state 0x2 cpu 4
> > [ 9515.833356] ??? Writer stall state RTWS_SYNC(21) g18446744073709551218 f0x0
> > ->state 0x2 cpu 4
> > 
> > It bisected to just this patch.
> 
> Looks like your getting rcutorture running on ARM was well timed!

And could you please send along your dmesg and .config files?

							Thanx, Paul