Oleg noticed that our checking of data.got_token is unsafe in the
cleanup case, and should really use a memory barrier. Use the
READ_ONCE/WRITE_ONCE helpers on got_token so we can be sure we're always
safe.
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
block/blk-rq-qos.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index 67a0a4c07060..f4aa7b818cf5 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -201,7 +201,7 @@ static int rq_qos_wake_function(struct wait_queue_entry *curr,
if (!data->cb(data->rqw, data->private_data))
return -1;
- data->got_token = true;
+ WRITE_ONCE(data->got_token, true);
list_del_init(&curr->entry);
wake_up_process(data->task);
return 1;
@@ -246,7 +246,7 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,
prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE);
has_sleeper = !wq_has_single_sleeper(&rqw->wait);
do {
- if (data.got_token)
+ if (READ_ONCE(data.got_token))
break;
if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
finish_wait(&rqw->wait, &data.wq);
@@ -256,7 +256,7 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,
* which means we now have two. Put our local token
* and wake anyone else potentially waiting for one.
*/
- if (data.got_token)
+ if (READ_ONCE(data.got_token))
cleanup_cb(rqw, private_data);
break;
}
--
2.17.1
