From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4FBC0582.2060707@xenomai.org> Date: Tue, 22 May 2012 23:30:42 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4FBADE7D.5030609@bbn.com> <4FBB4951.5070803@xenomai.org> <4FBC0383.3020608@bbn.com> In-Reply-To: <4FBC0383.3020608@bbn.com> 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: Mitchell Tasman Cc: xenomai@xenomai.org On 05/22/2012 11:22 PM, Mitchell Tasman wrote: > Gilles, > > On 05/22/2012 04:07 AM, Gilles Chanteperdrix wrote: >> On 05/22/2012 02:31 AM, Mitchell Tasman wrote: >>> Hi. I'm running an OMAP DM3725-based board with a 2.6.38.8 kernel, a >>> mid-May 2012 git snapshot of xenomai-2.6, and a backport (really just >>> application) of the patch that Gilles referenced in the "IRQ latency" >>> thread last week: >>> >>> http://git.xenomai.org/?p=ipipe-gch.git;a=commit;h=81bfc05c4716b76e79f5e486baf4c52015a3b92c >> >> Please try the following patch instead: > > Thank you very much for your prompt and most helpful response. > > I have applied the patch that you supplied, and find a dramatic > reduction in the maximum latency experienced in servicing edge-triggered > GPIO interrupts. In testing so far today with the new patch, I have not > encountered a single instance of the sort of extreme latency that > prompted my query to the mailing list. > > Might you consider applying the new patch to I-Pipe for ARM 2.6.38.8, > and publishing a new revision of that patch set? This could be of > significant benefit to those members of the Xenomai community that are > presently using a 2.6.38.8 kernel on ARM platforms. > > You might also consider addressing/replacing the original "ipipe/arm: > defer chained interrupts handling" patch that was applied to I-Pipe for > ARM 3.0.13, if the new patch is relevant to that kernel as well. > > Thanks again and Best Regards, Yes, that's the plan. I am just waiting for Jean-Pascal's result to confirm that everything is fine. Regards. -- Gilles.