linux-kernel - Re: [PATCH] USB: Fix the issue of task recovery failure caused by USB status when S4 wakes up

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Message-ID: <8b07752d-63c4-41e3-bd20-ce3da43dfffc@rowland.harvard.edu>
Date: Wed, 11 Sep 2024 10:40:33 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: duanchenghao <duanchenghao@...inos.cn>
Cc: gregkh@...uxfoundation.org, pavel@....cz, linux-pm@...r.kernel.org,
	niko.mauno@...sala.com, stanley_chang@...ltek.com, tj@...nel.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH] USB: Fix the issue of task recovery failure caused by
 USB status when S4 wakes up

On Tue, Sep 10, 2024 at 05:36:56PM +0800, duanchenghao wrote:
> S4 wakeup restores the image that was saved before the system entered
> the S4 sleep state.
> 
>     S4 waking up from hibernation
>     =============================
>     kernel initialization
>     |   
>     v   
>     freeze user task and kernel thread
>     |   
>     v   
>     load saved image
>     |    
>     v   
>     freeze the peripheral device and controller
>     (Check the HCD_FLAG_WAKEUP_ PENDING flag of the USB. If it is set,
>      return to EBUSY and do not perform the following restore image.)

Why is the flag set at this point?  It should not be; the device and 
controller should have been frozen with wakeup disabled.

>     |
>     v
>     restore image(task recovery)

> > > However, upon detecting that the hcd is in the
> > > HCD_FLAG_WAKEUP_PENDING state,
> > > it will return an EBUSY status, causing the S4 suspend to fail and
> > > subsequent task recovery to not proceed.
> > 
> > What will return an EBUSY status?
> 
> if HCD_FLAG_WAKEUP_PENDING flag is set_bit, will return EBUSY.

I meant: Which function will return EBUSY status?  The answer is in the 
log below; hcd_pci_suspend() does this.

> > Why do you say that S4 suspend will fail?  Aren't you talking about
> > S4 
> > wakeup?
> 
> After returning EBUSY, the subsequent restore image operation will not
> be executed.
> 
> > 
> > Can you provide a kernel log that explains these points and shows
> > what 
> > problem you are trying to solve?
> 
> [    9.009166][ 2] [  T403] PM: Image signature found, resuming
> [    9.009167][ 2] [  T403] PM: resume from hibernation
> [    9.009243][ 2] [  T403] inno-codec inno-codec.16.auto:
> [inno_vpu][vpu_notifier:1540]vpu_notifier: untested action 5...
> [    9.009244][ 2] [  T403] Freezing user space processes ... (elapsed
> 0.001 seconds) done.
> [    9.010355][ 2] [  T403] OOM killer disabled.
> [    9.010355][ 2] [  T403] Freezing remaining freezable tasks ...
> (elapsed 0.000 seconds) done.
> [    9.012152][ 2] [  T403] PM: Basic memory bitmaps created
> [    9.073333][ 2] [  T403] PM: Using 3 thread(s) for decompression
> [    9.073334][ 2] [  T403] PM: Loading and decompressing image data
> (486874 pages)...
> [    9.073335][ 2] [  T403] hibernate: Hibernated on CPU 0 [mpidr:0x0]
> [    9.095928][ 2] [  T403] PM: Image loading progress:   0%
> [    9.664803][ 2] [  T403] PM: Image loading progress:  10%
> [    9.794156][ 2] [  T403] PM: Image loading progress:  20%
> [    9.913001][ 2] [  T403] PM: Image loading progress:  30%
> [   10.034331][ 2] [  T403] PM: Image loading progress:  40%
> [   10.154070][ 2] [  T403] PM: Image loading progress:  50%
> [   10.277096][ 2] [  T403] PM: Image loading progress:  60%
> [   10.398860][ 2] [  T403] PM: Image loading progress:  70%
> [   10.533760][ 2] [  T403] PM: Image loading progress:  80%
> [   10.659874][ 2] [  T403] PM: Image loading progress:  90%
> [   10.760681][ 2] [  T403] PM: Image loading progress: 100%
> [   10.760693][ 2] [  T403] PM: Image loading done
> [   10.760718][ 2] [  T403] PM: Read 1947496 kbytes in 1.68 seconds
> (1159.22 MB/s)
> [   10.761982][ 2] [  T403] PM: Image successfully loaded
> [   10.761988][ 2] [  T403] printk: Suspending console(s) (use
> no_console_suspend to debug)
> [   10.864973][ 2] [  T403] innovpu_freeze:1782
> [   10.864974][ 2] [  T403] innovpu_suspend:1759
> [   11.168871][ 2] [  T189] PM: pci_pm_freeze():
> hcd_pci_suspend+0x0/0x38 returns -16

This should not be allowed to happen.  Freezing is mandatory and not 
subject to wakeup requests.

Is your problem related to the one discussed in this email thread?

https://lore.kernel.org/linux-usb/d8600868-6e4b-45ab-b328-852b6ac8ecb5@rowland.harvard.edu/

Would the suggestion I made there -- i.e., have the xhci-hcd 
interrupt handler skip calling usb_hcd_resume_root_hub() if the root hub 
was suspended with wakeup = 0 -- fix your problem?

Alan Stern