linux-kernel - Re: [PATCH 2/5] rcu/nocb: Move rcu_nocb_is_setup to rcu

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Message-ID: <20220216213035.GA2442742@paulmck-ThinkPad-P17-Gen-1>
Date:   Wed, 16 Feb 2022 13:30:35 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 2/5] rcu/nocb: Move rcu_nocb_is_setup to rcu_state

On Wed, Feb 16, 2022 at 04:42:05PM +0100, Frederic Weisbecker wrote:
> In order to avoid scattering the global RCU states, move the RCU nocb
> initialization witness within rcu_state.
> 
> Reported-by: Paul E. McKenney <paulmck@...nel.org>
> Cc: Neeraj Upadhyay <quic_neeraju@...cinc.com>
> Cc: Uladzislau Rezki <uladzislau.rezki@...y.com>
> Cc: Joel Fernandes <joel@...lfernandes.org>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Build testing for CONFIG_NO_HZ_FULL=n kernels suggested the following
patch be merged into this one.  Or does this variable need to be used
somewhere?  Either way, please let me know!

							Thanx, Paul

------------------------------------------------------------------------

commit 1a4f308b3b3841ef10043fe6c3dd12fc872b0400
Author: Paul E. McKenney <paulmck@...nel.org>
Date:   Wed Feb 16 13:27:42 2022 -0800

    squash! rcu/nocb: Move rcu_nocb_is_setup to rcu_state
    
    [ paulmck: Remove unused need_rcu_nocb_mask local variable. ]
    
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 9d6d4786bc703..9d97aa1f4d6ce 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1154,14 +1154,8 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
 void __init rcu_init_nohz(void)
 {
 	int cpu;
-	bool need_rcu_nocb_mask = false;
 	struct rcu_data *rdp;
 
-#if defined(CONFIG_NO_HZ_FULL)
-	if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask))
-		need_rcu_nocb_mask = true;
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
 	if (rcu_state.nocb_is_setup) {
 		if (!cpumask_available(rcu_nocb_mask)) {
 			if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {