在 2024/4/19 0:14, Tejun Heo 写道:
Hello,
On Thu, Apr 18, 2024 at 03:23:40PM +0800, linan666@xxxxxxxxxxxxxxx wrote:
From: Li Nan <linan122@xxxxxxxxxx>
In iocg_pay_debt(), warn is triggered if 'active_list' is empty, which
is intended to confirm iocg is avitve when it has debt. However, warn
can be triggered during removing cgroup controller, as
Maybe saying "a blkcg is being removed" is clearer?
Thanks for your suggestion. I will correct my expression in next version.
iocg_waitq_timer_fn() is awakened at that time.
WARNING: CPU: 0 PID: 2344971 at block/blk-iocost.c:1402 iocg_pay_debt+0x14c/0x190
Call trace:
iocg_pay_debt+0x14c/0x190
iocg_kick_waitq+0x438/0x4c0
iocg_waitq_timer_fn+0xd8/0x130
__run_hrtimer+0x144/0x45c
__hrtimer_run_queues+0x16c/0x244
hrtimer_interrupt+0x2cc/0x7b0
The warn in this situation is meaningless. Since this iocg is being
removed, the state of the 'active_list' is irrelevant, and 'waitq_timer'
is canceled after removing 'active_list' in ioc_pd_free(), which ensure
iocg is freed after iocg_waitq_timer_fn() returns.
Therefore, add the check if iocg has already offlined to avoid warn
when removing cgroup controller.
Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
---
block/blk-iocost.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index baa20c85799d..2e109c016a39 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1440,7 +1440,7 @@ static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay,
lockdep_assert_held(&iocg->waitq.lock);
/* make sure that nobody messed with @iocg */
- WARN_ON_ONCE(list_empty(&iocg->active_list));
+ WARN_ON_ONCE(list_empty(&iocg->active_list) && iocg->pd.online);
Can you add a comment explaining why we need the pd.online test?
Yeah, I will add comment in next version.
Other than the above nits, looks great to me. Please feel free to add
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Thanks.
--
Thanks,
Nan
