From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35B9BC2D0DB for ; Wed, 22 Jan 2020 15:04:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 074C921734 for ; Wed, 22 Jan 2020 15:04:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728760AbgAVPEL (ORCPT ); Wed, 22 Jan 2020 10:04:11 -0500 Received: from mga17.intel.com ([192.55.52.151]:47395 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbgAVPEK (ORCPT ); Wed, 22 Jan 2020 10:04:10 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Jan 2020 07:04:10 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,350,1574150400"; d="scan'208";a="284049874" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.163]) by fmsmga001.fm.intel.com with SMTP; 22 Jan 2020 07:04:05 -0800 Received: by lahna (sSMTP sendmail emulation); Wed, 22 Jan 2020 17:04:04 +0200 Date: Wed, 22 Jan 2020 17:04:04 +0200 From: Mika Westerberg To: Greg Kroah-Hartman Cc: Andy Shevchenko , Darren Hart , Lee Jones , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , x86@kernel.org, Zha Qipeng , "David E . Box" , Guenter Roeck , Heikki Krogerus , Wim Van Sebroeck , Mark Brown , platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 14/38] platform/x86: intel_scu_ipc: Introduce new SCU IPC API Message-ID: <20200122150404.GZ2665@lahna.fi.intel.com> References: <20200121160114.60007-1-mika.westerberg@linux.intel.com> <20200121160114.60007-15-mika.westerberg@linux.intel.com> <20200122134359.GE4963@kroah.com> <20200122144048.GV2665@lahna.fi.intel.com> <20200122144939.GA59473@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200122144939.GA59473@kroah.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 22, 2020 at 03:49:39PM +0100, Greg Kroah-Hartman wrote: > On Wed, Jan 22, 2020 at 04:40:48PM +0200, Mika Westerberg wrote: > > On Wed, Jan 22, 2020 at 02:43:59PM +0100, Greg Kroah-Hartman wrote: > > > > + if (!scu->dev) > > > > + goto err_unlock; > > > > + if (!try_module_get(scu->dev->driver->owner)) > > > > + goto err_unlock; > > > > + mutex_unlock(&ipclock); > > > > + return scu; > > > > > > NO REFERENCE COUNT INCREMENT??? > > > > You mean increment the scu->dev reference count? I kind of thought that > > the try_module_get() should make sure the thing stays there as long as > > the caller has not called _put() but now when I think about it bit more > > we would need to do device_get() here as well. > > module reference counts handle _code_ while structure reference counts > handle _data_. > > You should almost never need to worry about module reference counts if > your code is structured properly, only handle the reference counts on > the pointers you throw around. > > The fact that you are even calling try_module_get() is a huge flag that > something is wrong here. Thanks for the explanation! I'll keep this in mind and make sure the next version has reference counting done accordingly.