On Tuesday 11 September 2012 14:44:30 Aaron Lu wrote:
> On Mon, Sep 10, 2012 at 12:45:51PM +0200, Oliver Neukum wrote:
> > On Monday 10 September 2012 17:16:22 Aaron Lu wrote:
> >
> > > +static int sr_resume(struct device *dev)
> > > +{
> > > + struct scsi_cd *cd;
> > > + struct scsi_sense_hdr sshdr;
> > > +
> > > + cd = dev_get_drvdata(dev);
> > > +
> > > + if (!cd->device->powered_off)
> > > + return 0;
> > > +
> > > + /* get the disk ready */
> > > + scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);
> > > +
> > > + /* if user wakes up the ODD, eject the tray */
> > > + if (cd->device->need_eject) {
> > > + cd->device->need_eject = 0;
> > > + if (!(cd->cdi.mask & CDC_CLOSE_TRAY))
> > > + sr_tray_move(&cd->cdi, 1);
> >
> > 1. Even if the door is locked?
>
> This piece of code of sr_resume is intended for ZPODD devices, for
> normal devices it will simply return as the powered_off flag will never
> be set for them.
>
> And for ZPODD devices, the door shouldn't be in locked state here since
> for it to enter power off state, "no medium inside" has to be satisfied
This is true only if the device is autosuspended. But sr_resume()
will also be called if the whole system was suspended.
What happens if the user presses the door button on the drive
while the system was suspended?
> and when there is no medium inside, we do not lock its door.
>
> > 2. sr_tray_move allocates memory with GFP_KERNEL. This smells of a deadlock.
>
> Sorry, don't get this. Can you please elaborate?
Suppose you need to wake up two devices for the same reason, a ZPODD and a hard
drive. The ZPODD is woken first and sr_resume() requests memory with GFP_KERNEL.
The VM layer decides to page out to the hard drive to be woken up -> deadlock.
Regards
Oliver
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