Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752578AbcDRNCN (ORCPT ); Mon, 18 Apr 2016 09:02:13 -0400 Received: from mail-vk0-f68.google.com ([209.85.213.68]:34538 "EHLO mail-vk0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752037AbcDRNCM convert rfc822-to-8bit (ORCPT ); Mon, 18 Apr 2016 09:02:12 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 18 Apr 2016 22:02:10 +0900 Message-ID: Subject: Re: rtc ds3232 call trace in kernel From: Akinobu Mita To: Qianyu Gong Cc: "alexandre.belloni@free-electrons.com" , Mingkai Hu , "rtc-linux@googlegroups.com" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1441 Lines: 59 2016-04-18 15:15 GMT+09:00 Qianyu Gong : > Hi Akinobu, > > > > I got an rtc call trace when booting 4.6 kernel on our board and I found it > > was caused by this patch: > > > > commit fc1dcb0b39dbb10d3290f2fcd6e154670f699166 > > Author: Akinobu Mita > > Date: Mon Mar 7 00:27:53 2016 +0900 > > > > rtc: ds3232: use rtc->ops_lock to protect alarm operations > > > > ds3232->mutex is used to protect for alarm operations which > > need to access status and control registers. > > > > But we can use rtc->ops_lock instead. rtc->ops_lock is held when most > > of rtc_class_ops methods are called, so we only need to explicitly > > acquire it from irq handler in order to protect form concurrent > > accesses. > > > > Signed-off-by: Akinobu Mita > > Signed-off-by: Alexandre Belloni > > > The problem is that rtc->ops_lock would be accessed in ds3232_irq() > > without being initialized as rtc_device_register() is called too late. You have already identified the root cause of this issue. > As I’m not familiar with rtc things, could I just revert the patch or you > already > > have a solution to this problem? Thanks in advance. Could you check if the problem is resolved by moving the call of devm_rtc_device_register() from the end of ds3232_probe() to just before registering irq handler?