On 02/13/2017 07:14 AM, Thomas Gleixner wrote:
> Gabriel reported the lockdep splat below while investigating something
> different.
>
> Explanation for the splat is in the function comment above
> del_timer_sync().
>
> I can reproduce it as well and it's clearly broken.
Agree, the disable logic is broken. The below isn't super pretty, but it
should do the trick for 4.10.
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c73a6fcaeb9d..838f07e2b64a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3758,7 +3758,7 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
}
#ifdef CONFIG_CFQ_GROUP_IOSCHED
-static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
+static bool check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
{
struct cfq_data *cfqd = cic_to_cfqd(cic);
struct cfq_queue *cfqq;
@@ -3775,15 +3775,7 @@ static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
* spuriously on a newly created cic but there's no harm.
*/
if (unlikely(!cfqd) || likely(cic->blkcg_serial_nr == serial_nr))
- return;
-
- /*
- * If we have a non-root cgroup, we can depend on that to
- * do proper throttling of writes. Turn off wbt for that
- * case, if it was enabled by default.
- */
- if (nonroot_cg)
- wbt_disable_default(cfqd->queue);
+ return nonroot_cg;
/*
* Drop reference to queues. New queues will be assigned in new
@@ -3804,9 +3796,13 @@ static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
}
cic->blkcg_serial_nr = serial_nr;
+ return nonroot_cg;
}
#else
-static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
+static inline bool check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
+{
+ return false;
+}
#endif /* CONFIG_CFQ_GROUP_IOSCHED */
static struct cfq_queue **
@@ -4448,11 +4444,12 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
const int rw = rq_data_dir(rq);
const bool is_sync = rq_is_sync(rq);
struct cfq_queue *cfqq;
+ bool disable_wbt;
spin_lock_irq(q->queue_lock);
check_ioprio_changed(cic, bio);
- check_blkcg_changed(cic, bio);
+ disable_wbt = check_blkcg_changed(cic, bio);
new_queue:
cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq || cfqq == &cfqd->oom_cfqq) {
@@ -4488,6 +4485,10 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
rq->elv.priv[0] = cfqq;
rq->elv.priv[1] = cfqq->cfqg;
spin_unlock_irq(q->queue_lock);
+
+ if (disable_wbt)
+ wbt_disable_default(q);
+
return 0;
}
--
Jens Axboe
