linux-kernel - Re: [PATCH] drvier: usb: dwc3: Fix runtime PM trying to activate child device xxx.dwc3 but parent is not active

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <056bd3b8-7d62-42e5-8b5d-4113a9ef769b@rowland.harvard.edu>
Date: Fri, 29 Aug 2025 20:46:21 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	ryan zhou <ryanzhou54@...il.com>, Roy Luo <royluo@...gle.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] drvier: usb: dwc3: Fix runtime PM trying to activate
 child device xxx.dwc3 but parent is not active

On Fri, Aug 29, 2025 at 08:13:07PM +0000, Thinh Nguyen wrote:
> ..shouldn't the PM core know that A was runtime suspended to not skip
> ->resume? (sorry I'm not an expert in the PM core, genuine question
> here).

This doesn't answer your question directly, but I would like to add some 
background.

There are subsystems/drivers that do want to resume their devices during 
system resume, even if the devices were in runtime suspend originally.  
At a minimum, the PM core doesn't want to take this choice away from 
them.

In fact, the USB subsystem was designed to run that way back when 
support for runtime PM was first added, and it hasn't been changed since 
-- although maybe it should be.  There are explicit mechanisms for 
telling the PM core that a device should be skipped during system 
resume; we could use them.

Regardless, I don't recall any discussions of the particular situation 
in this thread ever taking place.

Alan Stern