linux-kernel - [PATCH 4.14 11/18] rcu: Fix up pending cbs check in rcu_prepare_for

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Date:   Wed, 22 Nov 2017 11:12:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Neeraj Upadhyay <neeraju@...eaurora.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH 4.14 11/18] rcu: Fix up pending cbs check in rcu_prepare_for_idle

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Neeraj Upadhyay <neeraju@...eaurora.org>

commit 135bd1a230bb69a68c9808a7d25467318900b80a upstream.

The pending-callbacks check in rcu_prepare_for_idle() is backwards.
It should accelerate if there are pending callbacks, but the check
rather uselessly accelerates only if there are no callbacks.  This commit
therefore inverts this check.

Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
Signed-off-by: Neeraj Upadhyay <neeraju@...eaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/rcu/tree_plugin.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1507,7 +1507,7 @@ static void rcu_prepare_for_idle(void)
 	rdtp->last_accelerate = jiffies;
 	for_each_rcu_flavor(rsp) {
 		rdp = this_cpu_ptr(rsp->rda);
-		if (rcu_segcblist_pend_cbs(&rdp->cblist))
+		if (!rcu_segcblist_pend_cbs(&rdp->cblist))
 			continue;
 		rnp = rdp->mynode;
 		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */