From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-15?Q?Martin_D=E4umler?= Subject: Priority Inheritance per se? Date: Fri, 10 Sep 2010 08:49:03 +0200 Message-ID: <4C89D4DF.9060109@cs.tu-chemnitz.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit To: linux-rt-users@vger.kernel.org Return-path: Received: from jack.hrz.tu-chemnitz.de ([134.109.132.46]:37367 "EHLO jack.hrz.tu-chemnitz.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751295Ab0IJH30 (ORCPT ); Fri, 10 Sep 2010 03:29:26 -0400 Received: from adelaide.informatik.tu-chemnitz.de ([134.109.192.66]) by jack.hrz.tu-chemnitz.de with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from ) id 1OtxPz-0006To-Ao for linux-rt-users@vger.kernel.org; Fri, 10 Sep 2010 08:49:03 +0200 Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hello, our team develops a Linux-based embedded system to realise a programmable logic controller. So we investigate several possibilities to augment Linux real-time capabilities. Naturally, the PREEMPT_RT-patch is interesting. I searched the wiki, the mailing list archive, listened to Mr. Assmann's talk at the Chemnitz Linux Days 2010 and read the corresponding chapter in "Building Embedded Linux Systems" by Karim Yaghmour. Nevertheless, I have a question to makes thinks clear once and for all: Does the priority inheritance mechanism work without using special (Pthread-) mutexes in userspace? (As far as I understood, it does not.) Imagine a hypothetical case: a high RT-priority (60) task triggers a synchronous/blocking system call which triggers a device driver whose ISR is a kernel thread with RT-priority 49. So, a medium RT-priority (55) task may block the high RT-priority task, doesn't it? With kind regards, Martin Daeumler