From f042a436c8dc9f9cfe8ed1ee5de372697269657d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 3 Jan 2020 16:27:00 -0800 Subject: [PATCH] rcutorture: Add READ_ONCE() to rcu_torture_count and rcu_torture_batch The rcutorture rcu_torture_count and rcu_torture_batch per-CPU variables are read locklessly, so this commit adds the READ_ONCE() to a load in order to avoid various types of compiler vandalism^Woptimization. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely and due to this being rcutorture. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 124160a610fa..0b9ce9a00623 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1413,8 +1413,8 @@ rcu_torture_stats_print(void) for_each_possible_cpu(cpu) { for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { - pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i]; - batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i]; + pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]); + batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]); } } for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) { -- 2.11.0