From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750907AbWAKDxx (ORCPT ); Tue, 10 Jan 2006 22:53:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751344AbWAKDxx (ORCPT ); Tue, 10 Jan 2006 22:53:53 -0500 Received: from ms-smtp-01.nyroc.rr.com ([24.24.2.55]:26347 "EHLO ms-smtp-01.nyroc.rr.com") by vger.kernel.org with ESMTP id S1750907AbWAKDxx (ORCPT ); Tue, 10 Jan 2006 22:53:53 -0500 Subject: Re: 2.6.15-rt3 + Open Posix Test Suite From: Steven Rostedt To: Daniel Walker Cc: Thomas Gleixner , mingo@elte.hu, linux-kernel@vger.kernel.org In-Reply-To: <1136934210.5756.13.camel@localhost.localdomain> References: <1136934210.5756.13.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 10 Jan 2006 22:53:12 -0500 Message-Id: <1136951593.6197.81.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2006-01-10 at 15:03 -0800, Daniel Walker wrote: > It's worth noting that a few tests in the current Open Posix Test Suite > hang RT systems. > > Specifically this test (hope this url comes through), > > http://cvs.sourceforge.net/viewcvs.py/*checkout*/posixtest/posixtestsuite/conformance/interfaces/sched_setparam/10-1.c?rev=1.2 > > sched_setparam test 10-1.c and I think 9-1.c . > > The 10-1 test spawns some children at SCHED_FIFO priority 99 , then runs > the following, > > void child_process(){ > alarm(2); > > while(1) { > (*shmptr)++; > sched_yield(); > } > } > > I'm sure this is what's hanging the system, the yield() is one issue. > Another is why the alarm() is never delivered . This runs a while loop at SCHED_FIFO prio 99? And alarm never happens. Doesn't the alarm get activated by the softirqd that is running at a lower priority? Seems that this is starving out the softirq from getting the alarm. I believe that Thomas once had priorities attached to the timers. I'd like to see that again, and may even start adding them myself, such that when a process activates a timer, when that timer goes off, the softirq will get the priority of the timer. But this has some complications to be sorted out. -- Steve