linux-kernel - Re: [linux-pm] Re: [PATCH] PM: Acquire device locks on suspend

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Message-Id: <200801070149.47958.rjw@sisk.pl>
Date:	Mon, 7 Jan 2008 01:49:47 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Johannes Berg" <johannes@...solutions.net>
Cc:	"Alan Stern" <stern@...land.harvard.edu>,
	"Greg KH" <gregkh@...e.de>, "LKML" <linux-kernel@...r.kernel.org>,
	"ACPI Devel Maling List" <linux-acpi@...r.kernel.org>,
	"pm list" <linux-pm@...ts.linux-foundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>
Subject: Re: [linux-pm] Re: [PATCH] PM: Acquire device locks on suspend

On Monday, 7 of January 2008, Rafael J. Wysocki wrote:
> On Monday, 7 of January 2008, Johannes Berg wrote:
> > Rafael J. Wysocki wrote:
> > 
> > >> I don't see anything wrong with it.  All that will happen is that the
> > >> removal will start before the suspend and finish after the resume.
> > >
> > > In that case, we'll attempt to call the device's .suspend() and .resume()
> > > routines, but we shouldn't do that, IMHO.
> > 
> > I don't see anything wrong with that since the driver must be prepared to
> > handle that even in the regular case, it's the only thing you can
> > guarantee: no more method calls after removal finishes. Am I totally
> > misunderstanding things?
> 
> Well, we are towards the end of device removal at this point, having called
> bus_remove_device(dev) for example, but still we've got it on dpm_active ...
> 
> This may not be technically wrong (ie. we should be able to recover from
> that), but it seems conceptually wrong and with pm_sleep_rwsem in place it
> can be avoided.

No, it can't, without major complications.

Well, I think I'll just send a patch that should work most of the time ...

Rafael
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