On 07/27/2018 06:24 AM, Bart Van Assche wrote:
> On Thu, 2018-07-26 at 10:45 +0800, jianchao.wang wrote:
>> On 07/26/2018 06:26 AM, Bart Van Assche wrote:
>>> @@ -102,9 +109,11 @@ int blk_pre_runtime_suspend(struct request_queue *q)
>>> return ret;
>>>
>>> blk_pm_runtime_lock(q);
>>> + blk_set_preempt_only(q);
>>
>> We only stop non-RQF_PM request entering when RPM_SUSPENDING and RPM_RESUMING.
>> blk_pre_runtime_suspend should only _check_ whether runtime suspend is allowed.
>> So we should not set preempt_only here.
>>
>>> + percpu_ref_switch_to_atomic_sync(&q->q_usage_counter);
>>>
>>> spin_lock_irq(q->queue_lock);
>>> - if (q->nr_pending) {
>>> + if (!percpu_ref_is_zero(&q->q_usage_counter)) {
>>> ret = -EBUSY;
>>> pm_runtime_mark_last_busy(q->dev);
>>> } else {
>>> @@ -112,6 +121,7 @@ int blk_pre_runtime_suspend(struct request_queue *q)
>>> }
>>> spin_unlock_irq(q->queue_lock);
>>>
>>> + percpu_ref_switch_to_percpu(&q->q_usage_counter);
>>> blk_pm_runtime_unlock(q);
>
> Hello Jianchao,
>
> There is only one caller of blk_post_runtime_suspend(), namely
> sdev_runtime_suspend(). That function calls pm->runtime_suspend() before
> it calls blk_post_runtime_suspend(). I think it would be wrong to set the
> PREEMPT_ONLY flag from inside blk_post_runtime_suspend() because that could
> cause pm->runtime_suspend() while a request is in progress.
>
Hi Bart
If q_usage_counter is not zero here, we will leave the request_queue in preempt only mode.
The request_queue should be set to preempt only mode only when we confirm we could set
rpm_status to RPM_SUSPENDING or RPM_RESUMING.
Maybe we could set the PREEMPT_ONLY after we confirm we could set the rpm_status
to RPM_SUSPENDING.
Something like:
percpu_ref_switch_to_atomic_sync(&q->q_usage_counter);
if (!percpu_ref_is_zero(&q->q_usage_counter)) {
ret = -EBUSY;
pm_runtime_mark_last_busy(q->dev);
} else {
blk_set_preempt_only(q);
if (!percpu_ref_is_zero(&q->q_usage_counter) {
ret = -EBUSY;
pm_runtime_mark_last_busy(q->dev);
blk_clear_preempt_only(q);
} else {
q->rpm_status = RPM_SUSPENDIN;
}
}
Thanks
Jianchao
