linux-kernel - [PATCH tip/core/rcu 09/12] rcu: Advance callbacks after migration

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Message-Id: <1500933116-11642-9-git-send-email-paulmck@linux.vnet.ibm.com>
Date:   Mon, 24 Jul 2017 14:51:53 -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,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 09/12] rcu: Advance callbacks after migration

When migrating callbacks from a newly offlined CPU, we are already
holding the root rcu_node structure's lock, so it costs almost nothing
to advance and accelerate the newly migrated callbacks.  This patch
therefore makes this advancing and acceleration happen.

Signed-off-by: Paul E. McKenney <paulmck@...ux.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 58ab489eca66..f9f01aeb5add 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3935,6 +3935,7 @@ static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp)
 	rcu_advance_cbs(rsp, rnp_root, rdp); /* Leverage recent GPs. */
 	rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
 	rcu_adopt_orphan_cbs(rsp, flags);
+	rcu_advance_cbs(rsp, rnp_root, my_rdp); /* Assign GP to pending CBs. */
 	raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags);
 	WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 ||
 		  !rcu_segcblist_empty(&rdp->cblist),
-- 
2.5.2