linux-kernel - [PATCH tip/core/rcu 09/10] rcu: Remove obsolete ->dynticks_fqs and ->cond_resched

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Message-Id: <20180829230735.10256-9-paulmck@linux.vnet.ibm.com>
Date:   Wed, 29 Aug 2018 16:07:34 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 09/10] rcu: Remove obsolete ->dynticks_fqs and ->cond_resched_completed

The rcu_data structure's ->dynticks_fqs is incremented but never
accesses.  Its ->cond_resched_completed field isn't used at all.
This commit therefore removes both fields.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c |  1 -
 kernel/rcu/tree.h | 12 +++---------
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ad09707d99ee..65b6e03ae6f5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1038,7 +1038,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 	 */
 	if (rcu_dynticks_in_eqs_since(rdp, rdp->dynticks_snap)) {
 		trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
-		rdp->dynticks_fqs++;
 		rcu_gpnum_ovf(rnp, rdp);
 		return 1;
 	}
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index af8681fec23b..bfbf97a1c29d 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -203,17 +203,11 @@ struct rcu_data {
 	int tick_nohz_enabled_snap;	/* Previously seen value from sysfs. */
 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 
-	/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
-	unsigned long dynticks_fqs;	/* Kicked due to dynticks idle. */
-	unsigned long cond_resched_completed;
-					/* Grace period that needs help */
-					/*  from cond_resched(). */
-
-	/* 5) rcu_barrier(), OOM callbacks, and expediting. */
+	/* 4) rcu_barrier(), OOM callbacks, and expediting. */
 	struct rcu_head barrier_head;
 	int exp_dynticks_snap;		/* Double-check need for IPI. */
 
-	/* 6) Callback offloading. */
+	/* 5) Callback offloading. */
 #ifdef CONFIG_RCU_NOCB_CPU
 	struct rcu_head *nocb_head;	/* CBs waiting for kthread. */
 	struct rcu_head **nocb_tail;
@@ -240,7 +234,7 @@ struct rcu_data {
 					/* Leader CPU takes GP-end wakeups. */
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 
-	/* 7) Diagnostic data, including RCU CPU stall warnings. */
+	/* 6) Diagnostic data, including RCU CPU stall warnings. */
 	unsigned int softirq_snap;	/* Snapshot of softirq activity. */
 	/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
 	struct irq_work rcu_iw;		/* Check for non-irq activity. */
-- 
2.17.1