From mboxrd@z Thu Jan 1 00:00:00 1970 References: From: Philippe Gerum Subject: Re: In-band Context Switch on oob_ioctl() call Date: Sat, 19 Feb 2022 16:29:26 +0100 In-reply-to: Message-ID: <877d9qho0c.fsf@xenomai.org> MIME-Version: 1.0 Content-Type: text/plain List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Russell Johnson Cc: xenomai@xenomai.org Russell Johnson via Xenomai writes: > Hello, > > I have added the oob_ioctl file descriptor to my driver, and I have > made sure that I call the necessary evl functions in the open() > function in the driver as well. I have a test app in userspace that is > simply opening the driver and issuing an oob_ioctl every second. What > I am seeing in the output from "evl ps -l" is that the "ISW" and > "CTXSW" fields are incrementing with every oob_ioctl call. I added in > the O_OOB flag to my open call, and I am still seeing the same > behavior. I don't get why it would be switching to in-band every time > the oob_ioctl() is called. Any ideas on what I could be doing wrong? > > Thanks, > Russell It looks like the calling thread is undergoing the so-called weak scheduling policy, see [1]. [1] https://evlproject.org/core/user-api/scheduling/#SCHED_WEAK -- Philippe.