Re: Allow runtime suspend during system resume

[Phillip Susi <psusi@ubuntu.com>]

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On 01/11/2014 05:50 PM, Alan Stern wrote:
> We won't.  The resume_early routine will set the status to
> RPM_ACTIVE or RPM_SUSPENDED, according to the result from 
> pm_runtime_usage_during_sleep.  It will also do a
> pm_runtime_get_sync on the disk's parent, to prevent the parent
> from going into runtime suspend before the async routine can run.
> 
> Then the async routine will do the following:
> 
> If the status is RPM_ACTIVE, spin up the disk.
> 
> Else (the status is RPM_SUSPENDED) check whether the disk has spun
> up by itself.  If it has, or if you can't tell, call 
> pm_runtime_resume to set the status correctly and do an explicit
> spin-up.
> 
> Call pm_runtime_put_sync on the parent.

I see now... thanks.

> I think this will give the desired result.  But there is one
> potential problem: If the disk has a child device (such as a
> partition) and the child's driver needs to do I/O as part of its
> resume routine, the I/O is likely to hang if the disk is runtime
> suspended.  However, I don't know of any child devices like this.

Probably should check dm and md to see if they do IO in their resume.


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