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From:   "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To:     linux-kernel@vger.kernel.org
Cc:     mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
        akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
        josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
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        fweisbec@gmail.com, oleg@redhat.com, joel.opensrc@gmail.com,
        torvalds@linux-foundation.org, npiggin@gmail.com,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 13/21] rcu: Clear request other than RCU_GP_FLAG_INIT at GP end
Date:   Sun, 22 Apr 2018 20:03:36 -0700
In-Reply-To: <20180423030258.GA23370@linux.vnet.ibm.com>
References: <20180423030258.GA23370@linux.vnet.ibm.com>
Message-Id: <1524452624-27589-13-git-send-email-paulmck@linux.vnet.ibm.com>
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Once the grace period has ended, any RCU_GP_FLAG_FQS requests are
irrelevant:  The grace period has ended, so there is no longer any
point in forcing quiescent states in order to try to make it end sooner.
This commit therefore causes rcu_gp_cleanup() to clear any bits other
than RCU_GP_FLAG_INIT from ->gp_flags at the end of the grace period.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c7b1e6b2a3da..25dbbc753fef 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2181,6 +2181,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 				       READ_ONCE(rsp->gpnum),
 				       TPS("newreq"));
 	}
+	WRITE_ONCE(rsp->gp_flags, rsp->gp_flags & RCU_GP_FLAG_INIT);
 	raw_spin_unlock_irq_rcu_node(rnp);
 }
 
-- 
2.5.2