linux-kernel - Re: [REGRESSION][BISECTED] 5.5-rc suspend/resume failure caused by patch a4f55d8b8c14 ("usb: hub: Check device descriptor before resusciation")

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Date:   Thu, 30 Jan 2020 14:16:57 -0700
From:   Paul Zimmerman <pauldzim@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     David Heinzelmann <heinzelmann.david@...il.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [REGRESSION][BISECTED] 5.5-rc suspend/resume failure caused by
 patch a4f55d8b8c14 ("usb: hub: Check device descriptor before resusciation")

Hi Alan,

On 1/23/20 8:50 AM, Alan Stern wrote:
> On Wed, 22 Jan 2020, Paul Zimmerman wrote:
> 
>>> Still, since there was no real connection change at the port, there's
>>> no reason to call hub_port_connect_change() here.  Let's see if the
>>> patch below fixes your problem.
>>>
>>> Alan Stern
>>>
>>>
>>>
>>> Index: usb-devel/drivers/usb/core/hub.c
>>> ===================================================================
>>> --- usb-devel.orig/drivers/usb/core/hub.c
>>> +++ usb-devel/drivers/usb/core/hub.c
>>> @@ -1216,11 +1216,6 @@ static void hub_activate(struct usb_hub
>>>   #ifdef CONFIG_PM
>>>   			udev->reset_resume = 1;
>>>   #endif
>>> -			/* Don't set the change_bits when the device
>>> -			 * was powered off.
>>> -			 */
>>> -			if (test_bit(port1, hub->power_bits))
>>> -				set_bit(port1, hub->change_bits);
>>>   
>>>   		} else {
>>>   			/* The power session is gone; tell hub_wq */
>>>
>>
>> I can confirm this fixes the issue for me, I did a couple dozen
>> suspend/resume cycles without seeing a failure.
>>
>> I see the code you removed was added by Lan Tianyu in commit
>> ad493e5e5805 ("usb: add usb port auto power off mechanism"). I
> 
> No, not really.  The set_bit() call was added by me in a much earlier
> commit (8808f00c7adf, merged in 2008).  Lan Tianyu merely added the
> "if" test, so that set_bit() doesn't always get called.  Now with this
> change, set_bit() never gets called.
> 
>> wonder if your patch would break that? I don't know what that is
>> or how to test it.
> 
> While some code review by people who are familiar with this material
> wouldn't hurt, I don't think you need to worry about any additional
> testing.
> 
>> In any case:
>> Tested-by: Paul Zimmerman <pauldzim@...il.com>
> 
> Thank you.  I'll submit the patch soon.
> 
> Alan Stern

Ping? Unfortunately 5.5 was released with this regression, do you plan
to submit this patch soon?

-- 
Paul