Re: REQ_PM vs REQ_TYPE_PM_RESUME

[Phillip Susi <psusi@ubuntu.com>]

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On 1/9/2014 11:14 AM, Alan Stern wrote:
> That's true, but it isn't a problem.  We know that requests with
> REQ_PM are sent only at certain, controlled times.  In particular,
> the only time such a request would be sent while the disk is
> RPM_SUSPENDED is during a system resume.

Yes, but if the disk and port were both already RPM_SUSPENDED when the
system was suspended, and so the port is still RPM_SUSPENDED when the
disk's system resume method is called, then it can't communicate with
the disk.

>> We need to put the device into one of the transitioning states
>> to block other IO, without allowing the port to suspend.
> 
> No, we only need to make sure that the port doesn't go into runtime
>  suspend while we carry out the "is the disk spinning" test.

Well how else do you do that other than with the transition states?


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