From: Joel Fernandes (Google) Date: Wed, 23 May 2018 06:38:15 +0000 (-0700) Subject: rcu: Identify grace period is in progress as we advance up the tree X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=226ca5e76692e2c82c17e8e8eedab22043f6ffee;p=linux.git rcu: Identify grace period is in progress as we advance up the tree There's no need to keep checking the same starting node for whether a grace period is in progress as we advance up the funnel lock loop. Its sufficient if we just checked it in the start, and then subsequently checked the internal nodes as we advanced up the combining tree. This also makes sense because the grace-period updates propogate from the root to the leaf, so there's a chance we may find a grace period has started as we advance up, lets check for the same. Reported-by: Paul McKenney Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 1af58f4b8a252..a6863b813f0c2 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1598,11 +1598,12 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, goto unlock_out; } rnp->gp_seq_needed = gp_seq_req; - if (rcu_seq_state(rcu_seq_current(&rnp_start->gp_seq))) { + if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) { /* - * We just marked the leaf, and a grace period - * is in progress, which means that rcu_gp_cleanup() - * will see the marking. Bail to reduce contention. + * We just marked the leaf or internal node, and a + * grace period is in progress, which means that + * rcu_gp_cleanup() will see the marking. Bail to + * reduce contention. */ trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startedleaf"));