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| author | Josef Bacik <josef@toxicpanda.com> | 2019-07-16 16:19:29 -0400 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-07-18 10:20:14 -0600 |
| commit | ac38297f7038cd5b80d66f8809c7bbf5b70031f3 (patch) | |
| tree | 2144d14a14682be1c068249731f6edcfda9e4ff4 | |
| parent | d14a9b389a86a5154b704bc88ce8dd37c701456a (diff) | |
| download | linux-ac38297f7038cd5b80d66f8809c7bbf5b70031f3.tar.bz2 | |
rq-qos: use a mb for got_token
Oleg noticed that our checking of data.got_token is unsafe in the
cleanup case, and should really use a memory barrier. Use a wmb on the
write side, and a rmb() on the read side. We don't need one in the main
loop since we're saved by set_current_state().
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-rq-qos.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c index c450b8952eae..3954c0dc1443 100644 --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -202,6 +202,7 @@ static int rq_qos_wake_function(struct wait_queue_entry *curr, return -1; data->got_token = true; + smp_wmb(); list_del_init(&curr->entry); wake_up_process(data->task); return 1; @@ -246,6 +247,7 @@ 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 { + /* The memory barrier in set_task_state saves us here. */ if (data.got_token) break; if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) { @@ -256,6 +258,7 @@ 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. */ + smp_rmb(); if (data.got_token) cleanup_cb(rqw, private_data); break; |