From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752410Ab2LSH40 (ORCPT ); Wed, 19 Dec 2012 02:56:26 -0500 Received: from h1446028.stratoserver.net ([85.214.92.142]:39649 "EHLO mail.ahsoftware.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751965Ab2LSH4V (ORCPT ); Wed, 19 Dec 2012 02:56:21 -0500 Message-ID: <50D1730D.7010108@ahsoftware.de> Date: Wed, 19 Dec 2012 08:55:57 +0100 From: Alexander Holler User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Andrew Morton CC: Vincent Palatin , rtc-linux@googlegroups.com, Alessandro Zummo , linux-kernel@vger.kernel.org, =?ISO-8859-1?Q?Lothar_Wa=DFmann?= Subject: Re: [rtc-linux] [PATCH] rtc: recycle id when unloading a rtc driver References: <1343951605-25722-1-git-send-email-vpalatin@chromium.org> <20121218164659.a3d3655a.akpm@linux-foundation.org> <50D16EA3.8040803@ahsoftware.de> <20121218234543.786a2211.akpm@linux-foundation.org> In-Reply-To: <20121218234543.786a2211.akpm@linux-foundation.org> Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 19.12.2012 08:45, schrieb Andrew Morton: > On Wed, 19 Dec 2012 08:37:07 +0100 Alexander Holler wrote: > >> Am 19.12.2012 01:46, schrieb Andrew Morton: >>> On Thu, 2 Aug 2012 16:53:25 -0700 >>> Vincent Palatin wrote: >>> >>>> When calling rtc_device_unregister, we are not freeing the id used by the >>>> driver. >>>> So when doing a unload/load cycle for a RTC driver (e.g. rmmod rtc_cmos >>>> && modprobe rtc_cmos), its id is incremented by one. As a consequence, >>>> we no longer have neither an rtc0 driver nor a /proc/driver/rtc (as it >>>> only exists for the first driver). >>>> >>>> Signed-off-by: Vincent Palatin >>>> --- >>>> drivers/rtc/class.c | 1 + >>>> 1 files changed, 1 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c >>>> index dc4c274..37b1d82 100644 >>>> --- a/drivers/rtc/class.c >>>> +++ b/drivers/rtc/class.c >>>> @@ -238,6 +238,7 @@ void rtc_device_unregister(struct rtc_device *rtc) >>>> rtc_proc_del_device(rtc); >>>> device_unregister(&rtc->dev); >>>> rtc->ops = NULL; >>>> + ida_simple_remove(&rtc_ida, rtc->id); >>>> mutex_unlock(&rtc->ops_lock); >>>> put_device(&rtc->dev); >>>> } >>> >>> Now I think about it, this shouldn't have been needed? >>> >>> That put_device() should call rtc_device_release(), which does the >>> ida_simple_remove(). Isn't that working? >> >> It is, see the mini-thread, patch and my comment here: >> >> https://lkml.org/lkml/2012/12/6/152 >> >> Maybe it would be better to move the ida_simple_remove from the >> rtc_device_release to rt_device_unregister as I've hinted in the above >> comment. That would make it easier to spot the ida_simple_remove(). > > 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). Regards, Alexander