linux-kernel - [PATCH tip/core/rcu 10/20] rcu: Remove obsolete force-quiescent-state statistics for debugfs

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Message-Id: <1519681990-31349-10-git-send-email-paulmck@linux.vnet.ibm.com>
Date:   Mon, 26 Feb 2018 13:53:00 -0800
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,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 10/20] rcu: Remove obsolete force-quiescent-state statistics for debugfs

The debugfs interface displayed statistics on RCU-pending checks but
this interface has since been removed.  This commit therefore removes the
no-longer-used rcu_state structure's ->n_force_qs_lh and ->n_force_qs_ngp
fields along with their updates.  (Though the ->n_force_qs_ngp field
was actually not used at all, embarrassingly enough.)

If this information proves necessary in the future, the corresponding
event traces will be added.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 5 +----
 kernel/rcu/tree.h | 4 ----
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 99d59be761d1..86fc087c7777 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2844,10 +2844,8 @@ static void force_quiescent_state(struct rcu_state *rsp)
 		      !raw_spin_trylock(&rnp->fqslock);
 		if (rnp_old != NULL)
 			raw_spin_unlock(&rnp_old->fqslock);
-		if (ret) {
-			rsp->n_force_qs_lh++;
+		if (ret)
 			return;
-		}
 		rnp_old = rnp;
 	}
 	/* rnp_old == rcu_get_root(rsp), rnp == NULL. */
@@ -2856,7 +2854,6 @@ static void force_quiescent_state(struct rcu_state *rsp)
 	raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
 	raw_spin_unlock(&rnp_old->fqslock);
 	if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
-		rsp->n_force_qs_lh++;
 		raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
 		return;  /* Someone beat us to it. */
 	}
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index d29bab8dea28..2edd56397b00 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -355,10 +355,6 @@ struct rcu_state {
 						/*  kthreads, if configured. */
 	unsigned long n_force_qs;		/* Number of calls to */
 						/*  force_quiescent_state(). */
-	unsigned long n_force_qs_lh;		/* ~Number of calls leaving */
-						/*  due to lock unavailable. */
-	unsigned long n_force_qs_ngp;		/* Number of calls leaving */
-						/*  due to no GP active. */
 	unsigned long gp_start;			/* Time at which GP started, */
 						/*  but in jiffies. */
 	unsigned long gp_activity;		/* Time of last GP kthread */
-- 
2.5.2