Re: [PATCH] block: Fix bug in runtime-resume handling

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On 24.08.20 22:13, Alan Stern wrote:
> On Mon, Aug 24, 2020 at 10:48:32AM -0700, Bart Van Assche wrote:
>> On 2020-08-23 07:57, Alan Stern wrote:
>>> The problem is fixed by checking that the queue's runtime-PM status
>>> isn't RPM_SUSPENDED before allowing a request to be issued, [ ... ]
>>
>> Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
>>
>> Can, can you help with testing this patch?
>>
>> Thanks,
>>
>> Bart.
> 
> Martin:
> 
> (I forgot to ask this question several weeks ago, while you were running 
> your tests.  Better ask it now before I forget again...)
> 
> I suspect the old runtime-PM code in the block layer would have worked 
> okay in your SD cardreader test if the BLK_MQ_REQ_PREEMPT flag had not 
> been set.  Do you know why the flag was set, or what line of code caused 
> it to be set?

Correct. if not set, I could handle all I need in the scsi error path.

> 
> As I recall, the request that failed was a read-ahead.  It's not clear 
> to me why such a request would need to have BLK_MQ_REQ_PREEMPT set.  
> Although there may be other reasons for having that flag, at this point 
> we're concerned with requests that are part of the runtime-resume 
> procedure.  A read-ahead does not fall into that category.
> 
> Do you think you can find the answer?  Perhaps we should add a separate 
> BLK_MQ_REQ_PM flag.

I guess I can but give me some time as I'm on vacations currently.

> 
> Alan Stern
> 



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