From: Li Nan <[email protected]>
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
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 <[email protected]>
---
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);
WARN_ON_ONCE(iocg->inuse > 1);
iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);
--
2.39.2
?? 2024/04/18 15:23, [email protected] д??:
> From: Li Nan <[email protected]>
>
> 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
> 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
This line doesn't match the code from mainline, please mention that
which kernel release you're testing.
Other than that, ioc_pd_free() indeed clear 'active_list' before
canceling the timer, this patch looks good to me.
Reviewed-by: Yu Kuai <[email protected]>
> 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 <[email protected]>
> ---
> 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);
> WARN_ON_ONCE(iocg->inuse > 1);
>
> iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);
>
在 2024/4/18 16:52, Yu Kuai 写道:
>
>
> 在 2024/04/18 15:23, [email protected] 写道:
>> From: Li Nan <[email protected]>
>>
>> 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
>> 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
>
> This line doesn't match the code from mainline, please mention that
> which kernel release you're testing.
>
Thanks for your review.
I tested at 5.10, but mainline has the same issue.
> Other than that, ioc_pd_free() indeed clear 'active_list' before
> canceling the timer, this patch looks good to me.
>
> Reviewed-by: Yu Kuai <[email protected]>
--
Thanks,
Nan
Hello,
On Thu, Apr 18, 2024 at 03:23:40PM +0800, [email protected] wrote:
> From: Li Nan <[email protected]>
>
> 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?
> 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 <[email protected]>
> ---
> 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?
Other than the above nits, looks great to me. Please feel free to add
Acked-by: Tejun Heo <[email protected]>
Thanks.
--
tejun
在 2024/4/19 0:14, Tejun Heo 写道:
> Hello,
>
> On Thu, Apr 18, 2024 at 03:23:40PM +0800, [email protected] wrote:
>> From: Li Nan <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>> 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 <[email protected]>
>
> Thanks.
>
--
Thanks,
Nan