From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756329Ab2LNPZM (ORCPT ); Fri, 14 Dec 2012 10:25:12 -0500 Received: from h1446028.stratoserver.net ([85.214.92.142]:46427 "EHLO mail.ahsoftware.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756248Ab2LNPZJ (ORCPT ); Fri, 14 Dec 2012 10:25:09 -0500 Message-ID: <50CB44B3.8040601@ahsoftware.de> Date: Fri, 14 Dec 2012 16:24:35 +0100 From: Alexander Holler User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20121002 Thunderbird/15.0.1 MIME-Version: 1.0 To: Lars-Peter Clausen CC: linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, Jonathan Cameron , rtc-linux@googlegroups.com, Alessandro Zummo , srinivas pandruvada , Andrew Morton Subject: Re: [PATCH 4/4 v4] rtc: add rtc-driver for HID sensors of type time References: <50C8591A.3030301@ahsoftware.de> <1355310680-2466-1-git-send-email-holler@ahsoftware.de> <50CAF473.6040901@metafoo.de> <50CB24D4.3030606@ahsoftware.de> <50CB347B.80305@ahsoftware.de> <50CB37C5.4050008@ahsoftware.de> <50CB38F2.4050806@metafoo.de> In-Reply-To: <50CB38F2.4050806@metafoo.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 14.12.2012 15:34, schrieb Lars-Peter Clausen: > On 12/14/2012 03:29 PM, Alexander Holler wrote: >> Am 14.12.2012 15:15, schrieb Alexander Holler: >>> Am 14.12.2012 14:08, schrieb Alexander Holler: >>>> Am 14.12.2012 10:42, schrieb Lars-Peter Clausen: >>> >>>>> And another thing I've overlooked before: >>>>> wait_for_completion_interruptible_timeout can either return a positive >>>>> number when the completion was completed, 0 in case of an timeout, or a >>>>> negative error code in case it was interrupted. You need to handle all >>>>> three. E.g. something like this. >>>>> >>>>> ret = wait_for_completion_interruptible_timeout(...) >>>>> if (ret == 0) >>>>> return -EIO; >>>>> if (ret < 0) >>>>> return ret >>>>> >>>> >>>> Hmpf, the only working approach to use some in kernel functions really >>>> is to the read source yourself and don't trust anything else. :/ >>> >>> Anyway, my approach doesn't work as it introduces a race condition: >>> >>> >>> /* get a report with all values through requesting one value */ >>> sensor_hub_input_attr_get_raw_value(...) >>> >>> /* race if this task goes to slepp and the values were >>> received before it could call the below wait... >>> >>> /* wait for all values (event) */ >>> if (!wait_for_completion_interruptible_timeout(...)) >>> >>> >>> I'll have to look for a mechanism how to avoid that. So v5 might need >>> some time. >> >> Sorry for the noise. That INIT_COMPLETION() before the sensor...() does >> exactly that. So it's enough if I handle the different return situations of >> wait_for...(). >> >> I will just use if(wait...()<=0) return -EIO. >> > > No, that's wrong. You should really return the error code returned by > wait_for_completion_interruptible_timeout(). This will make sure that > userspace restarts the syscall if necessary. Sorry for my ignorance, but which reasons for interruption do exist which doesn't kill the userspace too? The error number -ESYSRESTART doesn't offer a hint. Alexander