linux-kernel - Re: [PATCH 5/5] opticon: Fix resume logic

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Date:	Wed, 7 Oct 2009 18:01:58 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Johan Hovold <jhovold@...il.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Alan Cox <alan@...ux.intel.com>,
	Alan Stern <stern@...land.harvard.edu>, greg@...ah.com,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 5/5] opticon: Fix resume logic

Am Mittwoch, 7. Oktober 2009 17:56:02 schrieb Johan Hovold:
> On Tue, Oct 06, 2009 at 11:23:31PM +0100, Alan Cox wrote:
> > On Tue, 6 Oct 2009 23:12:17 +0200
> >
> > Oliver Neukum <oliver@...kum.org> wrote:
> > > Am Dienstag, 6. Oktober 2009 17:06:57 schrieb Alan Cox:
> > > > Opticon now takes the right mutex to check the port status but the
> > > > status check is done wrongly for the modern serial code, so fix it.
> > >
> > > As Alan Stern noticed, it seems like we have an ab-ba deadlock here
> > > between open and resume regarding pm_mutex and port->mutex.
> >
> > Oh well I guess someone with hardware will have to fix that.
> >
> > Do we actually need a separate pm_mutex anyway ?
>
> The pm_mutex is actually not aquired during open (and Alan Stern just
> confirmed that), so there is no dead-lock with port->mutex.

This is currently true, but will no longer be true if autosuspend is
implemented for this driver.

	Regards
		Oliver

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