Re: [PATCH v12 7/9] libata: scsi: no poll when ODD is powered off

[Tejun Heo <tj@kernel.org>]

Hello, Aaron.

On Fri, Jan 11, 2013 at 10:11:10AM +0800, Aaron Lu wrote:
> > What's the synchronization rule for this field?
> 
> I documented the rule in include/scsi/scsi_device.h.
> 
> This field is modified in the ata port's runtime suspend and resume
> callback, and is read accessed in the check_events callback of the sr
> block driver. The runtime PM callback is synchronized by PM core, in
> that the two callbacks will never run concurrently. So I guess saying
> synchronized by PM core is enough for this field?
> 
> This is what I've added in v12 for scsi_device structure:
> 
> +	bool disable_disk_events; /* disable poll for disk events, used in
> +				   * ATA layer, sychronized by PM core */
> +
> 
> Or do you mean I should add a comment explaining the sync rule when it
> is modifed, like in the above code?

The thing is that disabling disk events doesn't necessarily have
anything to do with PM, so tying synchronization to PM subsystem is a
bit unexpected.  How about making it an atomic_t?  That way, disabling
can stack and synchronization dependency to PM is removed.

Thanks.

-- 
tejun