linux-kernel - Re: [PATCH] rcu: Register rcu-lazy shrinker only CONFIG_RCU

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Message-ID: <20230130172731.GT2948950@paulmck-ThinkPad-P17-Gen-1>
Date:   Mon, 30 Jan 2023 09:27:31 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Zqiang <qiang1.zhang@...el.com>, frederic@...nel.org,
        quic_neeraju@...cinc.com, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: Register rcu-lazy shrinker only CONFIG_RCU_LAZY is
 enabled

On Mon, Jan 30, 2023 at 10:00:42AM -0500, Joel Fernandes wrote:
> On Mon, Jan 30, 2023 at 2:12 AM Zqiang <qiang1.zhang@...el.com> wrote:
> >
> > The rcu-lazy shrinker is registered without CONFIG_RCU_LAZY enabled
> > is meaningless, this commit therefore make rcu-lazy shrinker is
> > registered only when CONFIG_RCU_LAZY is enabled.
> >
> > Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> 
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

Queued and pushed, thank you both!

Twice, actually.  I missed Joel's reviewed-by the first time around,
fixed now.

							Thanx, Paul

> Thanks.
> 
> > ---
> >  kernel/rcu/tree_nocb.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
> > index 9e1c8caec5ce..28c1c092817b 100644
> > --- a/kernel/rcu/tree_nocb.h
> > +++ b/kernel/rcu/tree_nocb.h
> > @@ -1312,6 +1312,7 @@ int rcu_nocb_cpu_offload(int cpu)
> >  }
> >  EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
> >
> > +#ifdef CONFIG_RCU_LAZY
> >  static unsigned long
> >  lazy_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
> >  {
> > @@ -1360,6 +1361,7 @@ static struct shrinker lazy_rcu_shrinker = {
> >         .batch = 0,
> >         .seeks = DEFAULT_SEEKS,
> >  };
> > +#endif
> >
> >  void __init rcu_init_nohz(void)
> >  {
> > @@ -1391,8 +1393,10 @@ void __init rcu_init_nohz(void)
> >         if (!rcu_state.nocb_is_setup)
> >                 return;
> >
> > +#ifdef CONFIG_RCU_LAZY
> >         if (register_shrinker(&lazy_rcu_shrinker, "rcu-lazy"))
> >                 pr_err("Failed to register lazy_rcu shrinker!\n");
> > +#endif
> >
> >         if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
> >                 pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
> > --
> > 2.25.1
> >