From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4FBF78FE.3020300@xenomai.org> Date: Fri, 25 May 2012 14:20:14 +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> In-Reply-To: <4FBF4E69.1010200@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 05/25/2012 11:18 AM, Mitchell Tasman wrote: > Gilles, > > On 05/22/2012 05:30 PM, Gilles Chanteperdrix wrote: >> On 05/22/2012 11:22 PM, Mitchell Tasman wrote: >>> 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. > >> Yes, that's the plan. I am just waiting for Jean-Pascal's result to >> confirm that everything is fine. > > I thought I'd report that testing of > adeos-ipipe-2.6.38.8-arm-1.18-06.patch plus the revised "IRQ Chaining" > patch that you e-mailed continues to show a dramatic reduction in the > maximum latency in servicing edge-triggered GPIO interrupts. Good news > as well is that the load on the Linux domain (e.g. dohell vs. idle) > appears to have much less effect on the latency in servicing such > interrupts than was previously the case. > > I noticed that Jean-Pascal reported success as well, on 23 May. > > Thank you once again for your excellent support, and I very much look > forward to the updated I-Pipe for ARM 2.6.38.8 patch set. You are welcome. The patch should be done during the week-end. -- Gilles.