Re: question on flushing buffers and spinning down disk

[Oliver Neukum <oliver@neukum.org>]

Am Freitag 28 September 2007 schrieb Alan Stern:
> On Fri, 28 Sep 2007, Oliver Neukum wrote:
> 
> > Am Donnerstag 27 September 2007 schrieb Alan Stern:
> > > Have you thought about how autoresume would fit into this picture?  I
> > > don't think you can rely on usb-storage telling the SCSI core to resume
> > > devices when it gets handed a command, because the commands to spin-up
> > > the drives would have to be transmitted first.  (The sample patch you
> 
> I had another look at your patch.  It calls scsi_device_quiesce(), 
> which causes all normal requests to be deferred.  Hence under normal 
> operation the device would never autoresume -- user requests would be 
> deferred and never sent to usb-storage.

Unless I am very mistaken, further down in storage_suspend, I call

+	/* In case of autosuspend device must be unblocked again */
+	if (us->pusb_dev->auto_pm) {
+err_unblock:
+		shost_for_each_device(sdev, host) {
+			if (sdev == sdev2) {
+				scsi_device_put(sdev);
+				break;
+			}
+			scsi_device_resume(sdev);

which again allows normal io, so the autoresume is triggered.
It may deadlock, you are right about that, but it is definitely triggered.
I verified that experimentally.

	Regards
		Oliver


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