From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4FD0679F.3020904@xenomai.org> Date: Thu, 07 Jun 2012 10:34:39 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4FBADE7D.5030609@bbn.com> <4FBB4951.5070803@xenomai.org> <4FBC0383.3020608@bbn.com> <4FBC0582.2060707@xenomai.org> <4FBF4E69.1010200@bbn.com> <4FBF78FE.3020300@xenomai.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] A possible mis-interaction between CONFIG_PREEMPT and GPIO IRQ handling for ARM, leading to extreme latency List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Eric Cc: xenomai@xenomai.org On 06/07/2012 09:44 AM, Eric Eric wrote: > Hi Gilles, I believe the problems I was having several months ago with > erratic timing on the Beagleboard when running dohell may be related > to this. I'm wondering if there are still plans to formally wrap the > patch into the official Xenomai tree? The erratic timing you are talking about were variations in the microsecond range. What this patch avoids are latencies in the millisecond range involving GPIO interrupts. So, definitely no, this patch will not change anything with your situation. But anyway, I do not believe what you described was really a problem. Yes, some things have more influence on latencies than other. This is inherent to the dual kernel solution. And anyway, as I told you at the time, if you want to know what cause the worst case latency of a latency run, run latency -f with the I-pipe tracer enabled. If you post us a latency trace, we may help you find if anything is wrong. -- Gilles.