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

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Date:	Mon, 7 Jan 2008 00:59:15 +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, 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.

Rafael
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