On Thu, Jan 12, 2023 at 04:07:07PM +0100, Frederic Weisbecker wrote:
> On Wed, Dec 21, 2022 at 11:26:22AM -0800, Paul E. McKenney wrote:
> > On Sat, Dec 17, 2022 at 01:02:03PM +0000, Zhang, Qiang1 wrote:
> > commit 5815245b56229198d5f5d0c48c26d3c0c53ee222
> > Author: Zqiang <qiang1.zhang@xxxxxxxxx>
> > Date: Wed Dec 21 11:15:43 2022 -0800
> >
> > rcu: Remove redundant call to rcu_boost_kthread_setaffinity()
> >
> > The rcu_boost_kthread_setaffinity() function is invoked at
> > rcutree_online_cpu() and rcutree_offline_cpu() time, early in the online
> > timeline and late in the offline timeline, respectively. It is also
> > invoked from rcutree_dead_cpu(), however, in the absence of userspace
> > manipulations (for which userspace must take responsibility), this call
> > is redundant with that from rcutree_offline_cpu(). This redundancy can
> > be demonstrated by printing out the relevant cpumasks
> >
> > This commit therefore removes the call to rcu_boost_kthread_setaffinity()
> > from rcutree_dead_cpu().
> >
> > Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Thank you! I will apply this on my next rebase.
Thanx, Paul
> Thanks!
>
>
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index c3255d27286c4..a6181b76fd5ab 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -4165,15 +4165,10 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
> > */
> > int rcutree_dead_cpu(unsigned int cpu)
> > {
> > - struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
> > - struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
> > -
> > if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
> > return 0;
> >
> > WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1);
> > - /* Adjust any no-longer-needed kthreads. */
> > - rcu_boost_kthread_setaffinity(rnp, -1);
> > // Stop-machine done, so allow nohz_full to disable tick.
> > tick_dep_clear(TICK_DEP_BIT_RCU);
> > return 0;
