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

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Date:   Tue, 29 Nov 2022 22:26:13 +0530
From:   Nitin Rawat <quic_nitirawa@...cinc.com>
To:     Tushar Nimkar <quic_tnimkar@...cinc.com>,
        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>, <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 11/21/2022 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