Commit-ID: f34f2f5852e556ee1c3b3b294571086b1791008a
Gitweb: https://git.kernel.org/tip/f34f2f5852e556ee1c3b3b294571086b1791008a
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 3 May 2018 13:40:25 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 12 Jul 2018 15:39:06 -0700
rcu: Move grace-period pre-init delay after pre-init
The main race with the early part of grace-period initialization appears
to be with CPU hotplug. To more fully open this race window, this commit
moves the rcu_gp_slow() from the beginning of the early initialization
loop to follow that loop, thus widening the race window, especially for
the rcu_node structures that are initialized last. This commit also
expands rcutree.gp_preinit_delay from 3 to 12, giving the same overall
delay in the grace period, but concentrated in the spot where it will
do the most good.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 2 +-
tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 50e4f7ebf8cf..c577cadcc4f8 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1900,7 +1900,6 @@ static bool rcu_gp_init(struct rcu_state *rsp)
* will handle subsequent offline CPUs.
*/
rcu_for_each_leaf_node(rsp, rnp) {
- rcu_gp_slow(rsp, gp_preinit_delay);
spin_lock(&rsp->ofl_lock);
raw_spin_lock_irq_rcu_node(rnp);
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
@@ -1945,6 +1944,7 @@ static bool rcu_gp_init(struct rcu_state *rsp)
raw_spin_unlock_irq_rcu_node(rnp);
spin_unlock(&rsp->ofl_lock);
}
+ rcu_gp_slow(rsp, gp_preinit_delay); /* Races with CPU hotplug. */
/*
* Set the quiescent-state-needed bits in all the rcu_node
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot
index 5d2cc0bd50a0..b79ddb9eb9e8 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot
@@ -1,5 +1,5 @@
rcutorture.onoff_interval=1 rcutorture.onoff_holdoff=30
-rcutree.gp_preinit_delay=3
+rcutree.gp_preinit_delay=12
rcutree.gp_init_delay=3
rcutree.gp_cleanup_delay=3
rcutree.kthread_prio=2
--
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