Re: [PATCH] driver core: Ensure proper suspend/resume ordering

From	"Rafael J. Wysocki" <rjw@rjwysocki.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH] driver core: Ensure proper suspend/resume ordering
Date	2015-09-16 03:10 +0200
Message-ID	<q99ou-5Xi-19@gated-at.bofh.it> (permalink)
References	<q93VM-5No-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tuesday, September 15, 2015 03:18:19 PM Alan Stern wrote:
> On Tue, 15 Sep 2015, Thierry Reding wrote:
> 
> > > There are a few things to watch out for.  Since the dpm_list gets
> > > modified during system sleep transitions, we would have to make sure
> > > that nothing gets probed during those times.  In principle, that's what
> > > the "prepare" stage is meant for, but there's still a race.  As long as
> > > no other kernel thread (such as the deferred probing mechanism) tries
> > > to probe a device once everything has been frozen, we should be okay.
> > > But if not, there will be trouble -- after the ->prepare callback runs, 
> > > the device is no longer on the dpm_list and so we don't want this patch 
> > > to put it back on that list.
> > 
> > Perhaps moving to the end of the list needs to be a little smarter. That
> > is it could check whether the device has been prepared for suspension or
> > not and only move when it hasn't?
> 
> Maybe.  But doesn't that mean it won't solve your problem completely?
> 
> > Then again, shouldn't the core even prohibit new probes once the suspend
> > has been triggered? Sounds like asking for a lot of trouble if it didn't
> > ...
> 
> The core prohibits new devices from being registered.  It does not 
> prohibit probes of existing devices, because they currently do not 
> affect the dpm_list.

Which may be a mistake, because it does affect callbacks executed during
suspend/resume (after successful probe the device potentially has a different
set of PM callbacks than before).

> In general, we rely on subsystems not to do any probing once a device 
> is suspended.  It's probably reasonable to ask them not to do any 
> probing once a device has gone through the "prepare" stage.

Right.

Question is when it should be allowed to probe again.  I guess at the same
time we allow registrations to to take place again?

Thanks,
Rafael

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Thread

[PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-10 12:20 +0200
  Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-10 13:00 +0200
  Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-10 23:50 +0200
    Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-11 14:10 +0200
      Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-11 21:10 +0200
        Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-12 00:10 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-12 19:50 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-15 02:50 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-15 16:30 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-16 02:40 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-16 15:50 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 21:30 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-17 01:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-17 17:50 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-18 02:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-18 02:10 +0200
        Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-15 18:20 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-15 21:20 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-16 03:10 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-16 15:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 19:00 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 19:10 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-16 15:20 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-16 21:30 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-17 02:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-17 04:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-17 19:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-17 20:50 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-17 23:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-18 02:20 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-18 18:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-19 01:10 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-21 11:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-21 16:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-22 02:00 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-22 03:30 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-22 02:40 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-17 07:50 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rafael@kernel.org> - 2015-09-17 20:20 +0200
                Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-17 21:30 +0200
      Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-12 00:20 +0200
        Re: [PATCH] driver core: Ensure proper suspend/resume ordering Thierry Reding <thierry.reding@gmail.com> - 2015-09-15 18:00 +0200
          Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-16 03:00 +0200
            Re: [PATCH] driver core: Ensure proper suspend/resume ordering Grygorii Strashko <grygorii.strashko@ti.com> - 2015-09-16 15:40 +0200
              Re: [PATCH] driver core: Ensure proper suspend/resume ordering "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-17 02:30 +0200
    Re: [PATCH] driver core: Ensure proper suspend/resume ordering Alan Stern <stern@rowland.harvard.edu> - 2015-09-11 16:10 +0200

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