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

[Paul E. McKenney]

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@xxxxxxxxxx>
> 
> 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!

							Thanx, Paul