Re: [PATCH v2 4/5] block, scsi: Rework runtime power management

[jianchao.wang]

On 07/26/2018 10:45 AM, jianchao.wang wrote:
> Hi Bart
> 
> 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);

In addition, .runtime_suspend is invoked under spinlock and irq-disabled.
So sleep is forbidden here.
Please refer to rpm_suspend

* This function must be called under dev->power.lock with interrupts disabled

Thanks
Jianchao
>>  
>>      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);
>