From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753592AbbLKEXw (ORCPT ); Thu, 10 Dec 2015 23:23:52 -0500 Received: from mailout3.w1.samsung.com ([210.118.77.13]:18752 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751855AbbLKEXt (ORCPT ); Thu, 10 Dec 2015 23:23:49 -0500 X-AuditID: cbfec7f4-f79026d00000418a-f9-566a4fd3fde1 Subject: Re: [PATCH] pwm: Avoid double mutex lock on pwm_enable To: Anand Moon References: <1448038740-2811-1-git-send-email-linux.amoon@gmail.com> <564FF287.8000201@samsung.com> Cc: Guenter Roeck , Thierry Reding , Javier Martinez Canillas , linux-pwm@vger.kernel.org, Linux Kernel , "linux-samsung-soc@vger.kernel.org" , Jonathan Richardson From: Krzysztof Kozlowski Message-id: <566A4FCE.2050303@samsung.com> Date: Fri, 11 Dec 2015 13:23:42 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-version: 1.0 In-reply-to: Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrOLMWRmVeSWpSXmKPExsVy+t/xq7qX/bPCDD7eFrd483YNk8X8La+Z LF6/MLS4vGsOm8Xdu6sYLWac38dksW7jLXaLJwvPMFn83DWPxYHTY9b9s2weO2fdZffY0g8k dn5vYPfo27KK0ePzJrkAtigum5TUnMyy1CJ9uwSujJm7F7AXPOCrWLIrrYHxEncXIweHhICJ xN6j+V2MnECmmMSFe+vZuhi5OIQEljJKzJ62mxHCecoocaX1MhtIlbCAvcSNO3+ZQWwRATWJ K09XsEIUXWOR2L1oOhOIwyxwhklizqUuFpAqNgFjic3Ll4B18wpoSezpesoKYrMIqEpM6T/K AnKGqECExKIdmRAlghI/Jt8Da+UUCJbYcuoBWAmzgLrElCm5IGFmAXmJzWveMk9gFJiFpGMW QtUsJFULGJlXMYqmliYXFCel5xrqFSfmFpfmpesl5+duYoQE/5cdjIuPWR1iFOBgVOLhXciR FSbEmlhWXJl7iFGCg1lJhPelA1CINyWxsiq1KD++qDQntfgQozQHi5I479xd70OEBNITS1Kz U1MLUotgskwcnFINjDku248p7vpd2yXxXf3+9tbrfKa99+d7ec9y6J6794uC6rZnJxPnPL99 YTrnsxSezvW6zBX7GdZNFHm4W6F6frQPr8iL7jlssdxeFmsj/D9seCjPOMFZx//3UtkZxyxW X3AKeXTgxwqfHX9Nlc4e49K7X+a4Un7Z8p7VU4NDs/X/dbocndLqEKLEUpyRaKjFXFScCAC8 ZsFDegIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11.12.2015 13:07, Anand Moon wrote: > Hi Krzysztof, > > On 22 November 2015 at 05:43, Krzysztof Kozlowski > wrote: >> 2015-11-22 3:14 GMT+09:00 Anand Moon : >>> Hi Krzysztof, [...] >> Yes, now you pasted the same warning I did... >> >> This is still the same issue. I already wrote it: >>> 1. BUG: sleeping function called from invalid context >>> 2. DEBUG_LOCKS_WARN_ON(in_interrupt()) >> >> We can repeat it many times but that won't change anything... >> >> Best regards, >> Krzysztof > > Would you consider below changes to fix the above issue. > I have tested this change by enabling CONFIG_DEBUG_ATOMIC_SLEEP > And I don't observed issue. > > 1. BUG: sleeping function called from invalid context > 2. DEBUG_LOCKS_WARN_ON(in_interrupt()) > > Please share your thought on this changes. > > root@odroidxu4:/usr/src/odroidxu3-4.y-devel# git diff drivers/pwm/core.c > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c > index d24ca5f..f3f6cf9 100644 > --- a/drivers/pwm/core.c > +++ b/drivers/pwm/core.c > @@ -506,6 +506,9 @@ int pwm_enable(struct pwm_device *pwm) > if (!pwm) > return -EINVAL; > > + if (!mutex_is_locked(&pwm->lock)) > + return -EINVAL; > + > mutex_lock(&pwm->lock); > > if (!test_and_set_bit(PWMF_ENABLED, &pwm->flags)) { First of all, Thierry suggested way of fixing this: "Any objections to simply removing it and make all users use a workqueue or some such if they need to control a PWM as a result of an interrupt trigger?" what is wrong with his approach? Second, you are writing something that looks like mutex-try-lock... which will fail the pwm_enable(). IMHO this *hides* the real issue and does not solve anything (except hiding also the warning). Best regards, Krzysztof