Commit-ID: 1be0085b515e786e962b9f2d03616209eb6eb9a7
Gitweb: http://git.kernel.org/tip/1be0085b515e786e962b9f2d03616209eb6eb9a7
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 3 Nov 2014 18:20:20 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 6 Jan 2015 11:02:48 -0800
rcu: Don't initiate RCU priority boosting on root rcu_node
Because there is no longer any preempted tasks on the root rcu_node, and
because there is no longer ever an rcub kthread for the root rcu_node,
this commit drops the code in force_qs_rnp() that attempts to awaken
the non-existent root rcub kthread. This is strictly a performance
enhancement, removing a root rcu_node ->lock acquisition and release
along with some tests in rcu_initiate_boost(), ending with the test that
notes that there is no rcub kthread.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 990b406..5a0a4c96 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2513,12 +2513,6 @@ static void force_qs_rnp(struct rcu_state *rsp,
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
- rnp = rcu_get_root(rsp);
- if (rnp->qsmask == 0) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
- smp_mb__after_unlock_lock();
- rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
- }
}
/*
--
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