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rcutorture: Fix rcu_torture_one_read()/rcu_torture_writer() data race

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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@kernel.org>
This commit is contained in:
Paul E. McKenney 2019-12-21 10:41:48 -08:00
parent beabc806f5
commit 202489101f
1 changed files with 6 additions and 4 deletions
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10
kernel/rcu/rcutorture.c
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@ -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;