netdev - Re: Hangs in r8152 connected to power management in kernels at least up v4.17-rc4

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Date:   Wed, 16 May 2018 12:09:51 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Hayes Wang <hayeswang@...ltek.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>, jslaby@...e.com
Subject: Re: Hangs in r8152 connected to power management in kernels at
 least up v4.17-rc4

Am Mittwoch, den 16.05.2018, 10:00 +0000 schrieb Hayes Wang:
> Oliver Neukum [mailto:oneukum@...e.com]
> > Sent: Wednesday, May 16, 2018 4:27 PM
> 
> [...]
> > > 
> > > Would usb_autopm_get_interface() take a long time?
> > > The driver would wake the device if it has suspended.
> > > I have no idea about how usb_autopm_get_interface() works, so I don't know
> > 
> > how to help.
> > 
> > Hi,
> > 
> > it basically calls r8152_resume() and makes a control request to the
> > hub. I think we are spinning in rtl8152_runtime_resume(), but where?
> > It has a lot of NAPI stuff. Any suggestions on how to instrument or
> > trace this?
> 
> Is rtl8152_runtime_resume() called? I don't see the name in the trace.

Good question. I see nothing else that could produce a live lock.
> 
> I guess the relative API in rtl8152_runtime_resume() are
> 		ops->disable		= rtl8153_disable;
> 		ops->autosuspend_en	= rtl8153_runtime_enable;
> 
> And I don't find any possible dead lock in rtl8152_runtime_resume().
> 
> Besides, I find a similar issue as following.
> https://www.spinics.net/lists/netdev/msg493512.html

Well, if we have an imbalance in NAPI it should strike whereever
it is used, not just in suspend(). Is there debugging for NAPI
we could activate?

	Regards
		Oliver