From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <51F5990B.9010600@xenomai.org> Date: Mon, 29 Jul 2013 00:19:55 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <51F3B976.3020802@163.com> In-Reply-To: <51F3B976.3020802@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Real Time about user thread List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: aking Cc: "xenomai@xenomai.org" On 07/27/2013 02:13 PM, aking wrote: > Hi,all Hi, > RTDM is in the xenoami domain , A thread or an interrupt can be in the xenomai or linux domain, but RTDM is a skin, so, it does not really make sense to say that it is in the xenomai domain. RTDM allows to create real-time threads or to register interrupt handlers which can be executed in the Xenomai domain, but also allows defining callback executed in Linux domain. > and it's driven by the IRQ so that could provide hard real time. RTDM is no more driven by IRQ than the Linux kernel is driven by IRQ, and this is not sufficient to provide hard real-time (otherwise, the Linux kernel would provide hard real-time). The mechanism allowing hard real-time response to interrupts is the so-called "Optimistic interrupt protection" scheme, see [1] for more details. > The userspace thread is in Linux domain(maybe?) Or maybe not, see above. , what mechanism > was implemented to provide a Linux userspace thread real time? > Thank you very much. > Xenomai uses the Adeos patch to allow executing user-space threads in Xenomai domain, see [1] for more detains, and implements the classic real-time scheduling policies, aka SCHED_FIFO and SCHED_RR to provide deterministic scheduling. [1] http://www.xenomai.org/documentation/branches/v2.3.x/pdf/Life-with-Adeos-rev-B.pdf -- Gilles.