From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4F29DE8A.3080009@domain.hid> Date: Wed, 01 Feb 2012 19:53:30 -0500 From: Mitchell Tasman MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Xenomai-help] Handler executed on behalf of rtdm_nrtsig_pend() appears to be running in Linux hardirq, rather than softirq, context List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: xenomai@xenomai.org Xenomai documents rtdm_nrtsig_pend() as follows: > The signal handler will run in soft-IRQ context of the non-real-time subsystem. Note the implications of this context, e.g. no invocation of blocking operations. As a result, I would have anticipated that when invoked from within the signal handler, in_irq() would return 0, while in_softirq() would return non-zero. Instead, I've found that in_irq() returns the value 0x10000, which (digging around in include/linux/hardirq.h) indicates that the hardirq count is 1. A partial Linux kernel stack backtrace, leading up to execution of the signal handler, is as follows: > [ 217.844177] [] (my_signalClient+0x24/0x48 [my_rtdm_driver]) from [] (__ipipe_sync_stage+0x164/0x198) > [ 217.844207] [] (__ipipe_sync_stage+0x164/0x198) from [] (ipipe_trigger_irq+0x14/0x20) > [ 217.844238] [] (ipipe_trigger_irq+0x14/0x20) from [] (gatekeeper_thread+0x1ac/0x398) It seems that there are at least several possibilities: 1. I've misunderstood the documentation, and the signal handler is intended to run in Linux hardirq context. If so, and I need softirq context, I'd need to schedule a tasklet from within the signal handler. 2. There's something broken about my specific environment. I am presently using a Beagleboard xM Rev C, running a TI 2.6.37-derived OMAP kernel from the staging tree on Arago, with a tailored (by me) version of the ARM I-pipe patchset for 2.6.37.6 that ships with Xenomai-2.6.0. The Xenomai version is also the as-released 2.6.0. 3. I've discovered a bug (or feature) in the rtdm_nrtsig_pend() implementation and/or in the underlying plumbing. Perhaps someone from the Xenomai community can comment. Thanks much.