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

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Message-ID: <8ca27fcb-b146-3ea7-a042-55f99e0ae3fb@quicinc.com>
Date:   Mon, 21 Nov 2022 11:38:16 +0530
From:   Tushar Nimkar <quic_tnimkar@...cinc.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        <linux-pm@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
CC:     <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        <bjorn.andersson@...nel.org>,
        Nitin Rawat <quic_nitirawa@...cinc.com>,
        <quic_mkshah@...cinc.com>, <quic_lsrao@...cinc.com>,
        <bvanassche@....org>, Peter Wang <peter.wang@...iatek.com>
Subject: Re: PM-runtime: supplier looses track of consumer during probe

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.

[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