linux-kernel - Re: [rtc-linux] [PATCH] rtc: recycle id when unloading a rtc driver

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Date:	Wed, 19 Dec 2012 00:27:22 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Alexander Holler <holler@...oftware.de>
Cc:	Vincent Palatin <vpalatin@...omium.org>,
	rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org,
	Lothar Waßmann <LW@...O-electronics.de>
Subject: Re: [rtc-linux] [PATCH] rtc: recycle id when unloading a rtc driver

On Wed, 19 Dec 2012 08:55:57 +0100 Alexander Holler <holler@...oftware.de> wrote:

> >
> > I'm all confused.
> >
> > Lothar's patch simply reverts Vincent's patch.  And that appears to be
> > the correct thing to so, as the ida_simple_remove() in
> > rtc_device_release() should be sufficient.
> >
> > But apparently that doesn't work, because Vincent was seeing the RTC
> > ID's increment rather than getting reused.
> >
> > Is it the case that rtc_device_release() is not being called sometimes?
> > If so, under what circumstances?
> 
> Maybe something (sysfs or whatever) still has a reference to it. Vincent 
> should check that.
> 
> But I'm sure the ID will be recycled with that put_device() in 
> unregister because I've got the same warning as Lothar did when 
> (porperly) removing an RTC (with kernel 3.7).

If, as appears to be the case, rtc_device_release() is not being called
then we're also leaking memory.  So yes please, it would be good if
someone who can reproduce the IDs-dont-decrease problem could dive in
and work out why ->release() isn't begin called.

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