linux-kernel - [tip: core/rcu] rcu: Move rcu_cpu_started per-CPU variable to rcu

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Date:   Fri, 09 Oct 2020 06:35:36 -0000
From:   "tip-bot2 for Paul E. McKenney" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Paul E. McKenney" <paulmck@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: core/rcu] rcu: Move rcu_cpu_started per-CPU variable to rcu_data

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     c0f97f20e5d97a1358ade650fcf6a322c0c9bc72
Gitweb:        https://git.kernel.org/tip/c0f97f20e5d97a1358ade650fcf6a322c0c9bc72
Author:        Paul E. McKenney <paulmck@...nel.org>
AuthorDate:    Fri, 24 Jul 2020 20:22:05 -07:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Mon, 24 Aug 2020 18:37:54 -07:00

rcu: Move rcu_cpu_started per-CPU variable to rcu_data

When the rcu_cpu_started per-CPU variable was added by commit
f64c6013a202 ("rcu/x86: Provide early rcu_cpu_starting() callback"),
there were multiple sets of per-CPU rcu_data structures.  Therefore, the
rcu_cpu_started flag was added as a separate per-CPU variable.  But now
there is only one set of per-CPU rcu_data structures, so this commit
moves rcu_cpu_started to a new ->cpu_started field in that structure.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 11 ++++-------
 kernel/rcu/tree.h |  1 +
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index da05afc..52108dd 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3967,8 +3967,6 @@ int rcutree_offline_cpu(unsigned int cpu)
 	return 0;
 }
 
-static DEFINE_PER_CPU(int, rcu_cpu_started);
-
 /*
  * Mark the specified CPU as being online so that subsequent grace periods
  * (both expedited and normal) will wait on it.  Note that this means that
@@ -3988,12 +3986,11 @@ void rcu_cpu_starting(unsigned int cpu)
 	struct rcu_node *rnp;
 	bool newcpu;
 
-	if (per_cpu(rcu_cpu_started, cpu))
+	rdp = per_cpu_ptr(&rcu_data, cpu);
+	if (rdp->cpu_started)
 		return;
+	rdp->cpu_started = true;
 
-	per_cpu(rcu_cpu_started, cpu) = 1;
-
-	rdp = per_cpu_ptr(&rcu_data, cpu);
 	rnp = rdp->mynode;
 	mask = rdp->grpmask;
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -4053,7 +4050,7 @@ void rcu_report_dead(unsigned int cpu)
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	raw_spin_unlock(&rcu_state.ofl_lock);
 
-	per_cpu(rcu_cpu_started, cpu) = 0;
+	rdp->cpu_started = false;
 }
 
 /*
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index c96ae35..309bc7f 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -156,6 +156,7 @@ struct rcu_data {
 	bool		beenonline;	/* CPU online at least once. */
 	bool		gpwrap;		/* Possible ->gp_seq wrap. */
 	bool		exp_deferred_qs; /* This CPU awaiting a deferred QS? */
+	bool		cpu_started;	/* RCU watching this onlining CPU. */
 	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
 	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */
 	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */