From: John Sigler Subject: Re: Pin-pointing the root of unusual application latencies Date: Wed, 25 Jul 2007 15:20:05 +0200 Message-ID: <46A74E05.50504@free.fr> References: <469600F7.3060603@free.fr> <20070723095357.GA886@elte.hu> <46A4B7C2.1070304@free.fr> <20070723160442.GA7995@elte.hu> <46A5B8E3.4060004@free.fr> <46A74A58.1070704@free.fr> <20070725130536.GA12334@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org To: Ingo Molnar Return-path: Received: from smtp4-g19.free.fr ([212.27.42.30]:57152 "EHLO smtp4-g19.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761975AbXGYNUJ (ORCPT ); Wed, 25 Jul 2007 09:20:09 -0400 In-Reply-To: <20070725130536.GA12334@elte.hu> Sender: linux-rt-users-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org (Dropping oprofile-list@lists.sourceforge.net) Ingo Molnar wrote: > John Sigler wrote: > >>> With a pair of the following in the middle: >>> >>> softirq--4 0.... 670us : call_rcu (rt_run_flush) >>> softirq--4 0D..1 670us : __rcu_advance_callbacks (call_rcu) > >> Any idea what went wrong in the above function trace? Why is the >> kernel spinning in circles that way? > > does your test-app have higher priority than softirq--4 ? PID 4 is [softirq-timer/0] and has priority 50 in SCHED_FIFO. My process has priority 80 in SCHED_RR. It is waiting for IRQ10. My user-space app has higher priority than everything except PID 2 which is [posix_cpu_timer] Is this a priority inversion issue? Regards.