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:   Fri, 31 Jan 2020 10:37:45 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Paul Zimmerman <pauldzim@...il.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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")

On Thu, 30 Jan 2020, Paul Zimmerman wrote:

> 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?

Oops.  It totally slipped my mind, sorry.  Thanks for reminding me.  
Submission coming up...

Alan Stern