From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philippe Gerum In-Reply-To: <18103.24835.247952.219162@domain.hid> References: <18103.24835.247952.219162@domain.hid> Content-Type: text/plain Date: Mon, 06 Aug 2007 21:27:13 +0200 Message-Id: <1186428434.5963.12.camel@domain.hid> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: Philippe Gerum Subject: Re: [Xenomai-help] newbie question Reply-To: rpm@xenomai.org List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: Xenomai-help@domain.hid On Mon, 2007-08-06 at 19:57 +0200, Gilles Chanteperdrix wrote: > rolfetas bambolas wrote: > > Hi to all, > > I'm trying to understand how Xenomai handles priorities, and found a paper > > called "Life with Adeos" from 2005 which explains that tasks in secondary > > mode force the linux kernel to inherit the RT-Tasks priority. > > I also read that User-Space RT Tasks migrate to secondary mode when they > > make a system call to the linux-kernel, and migrate back when they use some > > Xenomai API. > > > > Does this mean, that the Linux-Kernel will keep the inherited priority until > > the RT-Task calls again Xenomai?? what happens is a RT-Task doesn't call > > Xenomai for a while?? > > I hope you understand what I mean, > > Thank you, > > What you are referring to is the priority coupling between Xenomai and > Linux schedulers, and can be disabled in Xenomai configuration. > > The linux kernel will keep the inherited priority until the RT-task > calls xenomai again, or until it is suspended by Linux scheduler. If the > RT-task does not call xenomai for a while (and is not suspended by Linux > scheduler), then, well, it is an RT-task after all and should be able to > run until it reaches a suspension point or wakes up another RT-task. > > Note however that during this time, Linux interruptions will be allowed > to preempt the RT-task. > (unless the interrupt shield is in effect). -- Philippe.