On Tue, Feb 16, 2016 at 09:45:49PM -0800, Paul E. McKenney wrote:
> On Tue, Feb 09, 2016 at 09:11:55PM +1100, Ross Green wrote:
> > Continued testing with the latest linux-4.5-rc3 release.
> >
> > Please find attached a copy of traces from dmesg:
> >
> > There is a lot more debug and trace data so hopefully this will shed
> > some light on what might be happening here.
> >
> > My testing remains run a series of simple benchmarks, let that run to
> > completion and then leave the system idle away with just a few daemons
> > running.
> >
> > the self detected stalls in this instance turned up after a days run time.
> > There were NO heavy artificial computational loads on the machine.
>
> It does indeed look quiet on that dmesg for a good long time.
>
> The following insanely crude not-for-mainline hack -might- be producing
> good results in my testing. It will take some time before I can claim
> statistically different results. But please feel free to give it a go
> in the meantime. (Thanks to Al Viro for pointing me in this direction.)
No joy, just a statistical anomaly. :-(
Thanx, Paul
> ------------------------------------------------------------------------
>
> commit 0c2c8d9fd1641809830a7a75f84dcad69936ef56
> Author: Paul E. McKenney <[email protected]>
> Date: Tue Feb 16 15:42:36 2016 -0800
>
> rcu: Crude exploratory hack
>
> Signed-off-by: Paul E. McKenney <[email protected]>
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 507d0ed48b97..5928e084620d 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2194,8 +2194,10 @@ static int __noreturn rcu_gp_kthread(void *arg)
> READ_ONCE(rsp->gpnum),
> TPS("fqswait"));
> rsp->gp_state = RCU_GP_WAIT_FQS;
> - ret = wait_event_interruptible_timeout(rsp->gp_wq,
> - rcu_gp_fqs_check_wake(rsp, &gf), j);
> + ret = schedule_timeout_interruptible(j > 0 ? j : 1);
> + rcu_gp_fqs_check_wake(rsp, &gf);
> + // ret = wait_event_interruptible_timeout(rsp->gp_wq,
> + // rcu_gp_fqs_check_wake(rsp, &gf), j);
> rsp->gp_state = RCU_GP_DOING_FQS;
> /* Locking provides needed memory barriers. */
> /* If grace period done, leave loop. */
