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

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Date:	Wed, 19 Dec 2012 09:55:02 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
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

Am 19.12.2012 09:27, schrieb Andrew Morton:
> 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.

Unlikely, as I've worked hard to get one of the first drivers for 
pluggable RTCs into the kernel. ;)
I think every sane kernel has them statically linked in and it's likely 
a problem of the RTC-driver Vincent experienced that with.

Regards,

Alexander
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