linux-kernel - [PATCH tip/core/rcu 16/22] rcu: Remove failsafe check for lost quiescent state

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Date:   Tue, 26 Jun 2018 10:10:42 -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 16/22] rcu: Remove failsafe check for lost quiescent state

Now that quiescent-state reporting is fully event-driven, this commit
removes the check for a lost quiescent state from force_qs_rnp().

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7de1820a04c1..8704b31b696d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2317,8 +2317,9 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
  * irqs disabled, and this lock is released upon return, but irqs remain
  * disabled.
  */
-static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
-				      struct rcu_node *rnp, unsigned long flags)
+static void __maybe_unused
+rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
+			  struct rcu_node *rnp, unsigned long flags)
 	__releases(rnp->lock)
 {
 	unsigned long gps;
@@ -2679,17 +2680,6 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp))
 				/* rcu_initiate_boost() releases rnp->lock */
 				continue;
 			}
-			if (rnp->parent &&
-			    (rnp->parent->qsmask & rnp->grpmask)) {
-				/*
-				 * Race between grace-period
-				 * initialization and task exiting RCU
-				 * read-side critical section: Report.
-				 */
-				rcu_report_unblock_qs_rnp(rsp, rnp, flags);
-				/* rcu_report_unblock_qs_rnp() rlses ->lock */
-				continue;
-			}
 			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 			continue;
 		}
-- 
2.17.1