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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 <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2020-01-03 16:27:00 -08:00
parent 102c14d2f8
commit f042a436c8
1 changed files with 2 additions and 2 deletions
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4
kernel/rcu/rcutorture.c
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@ -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--) {