Re: PM-runtime: supplier looses track of consumer during probe

[Nitin Rawat]

Hi Adrian,

On 11/21/2022 11:38 AM, Tushar Nimkar wrote:
> Hi Adrian,
>
> On 11/18/2022 8:25 PM, Adrian Hunter wrote:
> > On 4/11/22 11:19, Tushar Nimkar wrote:
> > > Hi linux-pm/linux-scsi,
>
> > > > Process -1
> > > > ufshcd_async_scan context (process 1)
> > > > scsi_autopm_put_device() //0:0:0:0
> >
> > I am having trouble following your description.  What function is calling
> > scsi_autopm_put_device() here?
> Below is flow which calls scsi_autopm_put_device()
> Process -1
> ufshcd_async_scan()
>      scsi_probe_and_add_lun()
>          scsi_add_lun()
>              slave_configure()
>                  scsi_sysfs_add_sdev()
>                      scsi_autopm_get_device()
>                          device_add()     <- invoked [Process 2] sd_probe()
>                              scsi_autopm_put_device()
>
> > > > pm_runtime_put_sync()
> > > > __pm_runtime_idle()
> > > > rpm_idle() -- RPM_GET_PUT(4)
> > > >       __rpm_callback
> > > >           scsi_runtime_idle()
> > > >               pm_runtime_mark_last_busy()
> > > >               pm_runtime_autosuspend()  --[A]
> > > >                   rpm_suspend() -- RPM_AUTO(8)
> > > >                       pm_runtime_autosuspend_expiration() 
> > > > use_autosuspend    is false return 0   --- [B]
> > > >                           __update_runtime_status to RPM_SUSPENDING
> > > >                       __rpm_callback()
> > > >                           __rpm_put_suppliers(dev, false)
> > > >                       __update_runtime_status to RPM_SUSPENDED
> > > >                   rpm_suspend_suppliers()
> > > >                       rpm_idle() for supplier -- RPM_ASYNC(1) return 
> > > > (-EAGAIN) [ Other consumer active for supplier]
> > > >                   rpm_suspend() – END with return=0
> > > >           scsi_runtime_idle() END return (-EBUSY) always.
> >
> > Not following here either.  Which device is EBUSY and why?
>
> scsi_runtime_idle() return -EBUSY always [3]
> Storage/scsi team can better explain -EBUSY implementation.

EBUSY is returned from below code for consumer dev 0:0:0:0.
scsi_runtime_idle is called from scsi_autopm_put_device which inturn is 
called from ufshcd_async_scan (Process 1 as per above call stack)
static int scsi_runtime_idle(struct device *dev)
{
	:

	if (scsi_is_sdev_device(dev)) {
		pm_runtime_mark_last_busy(dev);
		pm_runtime_autosuspend(dev);
		return -EBUSY; ---> EBUSY returned from here.
	}

	
}

> [3] 
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/scsi/scsi_pm.c?h=next-20221118#n210
>
>
> > > > [1]: https://lore.kernel.org/lkml/4748074.GXAFRqVoOG@kreacher/T/
> > > > [2]: https://lkml.org/lkml/2022/10/12/259
> > > >
> > > > Thanks,
> > > > Tushar Nimkar
> Thanks,
> Tushar Nimkar

Thanks,
Nitin