From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
The ->rtort_pipe_count field in the rcu_torture structure checks for
too-short grace periods, and is therefore read by rcutorture's readers
while being updated by rcutorture's writers. This commit therefore
adds the needed READ_ONCE() and WRITE_ONCE() invocations.
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@xxxxxxxxxx>
---
kernel/rcu/rcutorture.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 5efd950..edd9746 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -375,11 +375,12 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp)
{
int i;
- i = rp->rtort_pipe_count;
+ i = READ_ONCE(rp->rtort_pipe_count);
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ WRITE_ONCE(rp->rtort_pipe_count, i + 1);
+ if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
rp->rtort_mbtest = 0;
return true;
}
@@ -1015,7 +1016,8 @@ rcu_torture_writer(void *arg)
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- old_rp->rtort_pipe_count++;
+ WRITE_ONCE(old_rp->rtort_pipe_count,
+ old_rp->rtort_pipe_count + 1);
switch (synctype[torture_random(&rand) % nsynctypes]) {
case RTWS_DEF_FREE:
rcu_torture_writer_state = RTWS_DEF_FREE;
@@ -1291,7 +1293,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
atomic_inc(&n_rcu_torture_mberror);
rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
preempt_disable();
- pipe_count = p->rtort_pipe_count;
+ pipe_count = READ_ONCE(p->rtort_pipe_count);
if (pipe_count > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
--
2.9.5
