From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <493818F5.1010209@domain.hid> Date: Thu, 04 Dec 2008 18:52:53 +0100 From: Wolfgang Grandegger MIME-Version: 1.0 References: <493306F5.2080605@domain.hid> <49330CD3.4090700@domain.hid> <4933BAE2.3000502@domain.hid> <4933F1A4.8060209@domain.hid> <4933F18F.7080103@domain.hid> <4933FE5A.5060501@domain.hid> <49355B5D.8070802@domain.hid> <49355A59.4050600@domain.hid> <49357C02.1090001@domain.hid> <49365C69.5040807@domain.hid> <49366B2B.4050705@domain.hid> <493689EB.8000300@domain.hid> <4936C9CA.1090507@domain.hid> <4936C897.1000406@domain.hid> <4936D1E7.4070006@domain.hid> <4936D0B9.6070102@domain.hid> <4936D63F.50501@domain.hid> <4936D63B.3050603@domain.hid> <4936DBC1.6030303@domain.hid> <4936DBC6.9080805@domain.hid> <4936E5EA.1060008@domain.hid> <4936E5EB.9080404@domain.hid> <4937F76D.7040906@domain.hid> <4937F961.1080605@domain.hid> <493805E3.30404@domain.hid> <49380498.9040505@domain.hid> <49380A1C.2000701@domain.hid> <49380D18.8000107@domain.hid> In-Reply-To: <49380D18.8000107@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] pthread cancelation and scheduling magics 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 Gilles Chanteperdrix wrote: > Wolfgang Grandegger wrote: >> Gilles Chanteperdrix wrote: >>> Wolfgang Grandegger wrote: >>>> Gilles Chanteperdrix wrote: >>>>> Wolfgang Grandegger wrote: >>>>>> Gilles Chanteperdrix wrote: >>>> [...deletions...] >>>>>>> That is not expected. But this brings me back to my initial question, do >>>>>>> you have to work with a real world application that runs without issuing >>>>>>> any syscall ? >>>>>> If a add long nanosleeps, e.g. 100, 10 or 1 ms, cancellation works but >>>>>> it fails with short nanosleeps. A syscall seems not sufficient. I have >>>>>> the impression that pthread_cancel needs some time in secondary mode to >>>>> When calling nanosleep, the threads spends on time in secondary mode. I >>>> What do you mean? nanosleep switches to secondary mode? >>> I meant spends "no" time in secondary mode. nanosleep does not switch to >>> secondary mode. >>> >>>>> think the problem is rather that only asynchronous cancelation (meaning >>>>> cancelation with a signal) works. Setting the cancelation bit somehow >>>>> gets lost. >>>>> >>>>>> do it's duties, e.g. mark the thread as canceled. Would it make sense to >>>>>> wrap pthread_cancel, and friends to the corresponding kernel functions >>>>>> in ksrc/skins/posix? >>>>>> Is there a way to force a thread switching to secondary mode? >>>>> No, there is no way to force a thread to switch to secondary mode, the >>>>> xnshadow_relax call explicitely requires to be called by the target >>>>> thread. Before I wrap pthread_cancel, I would really like to understand >>>>> why setting a bit with pthread_cancel and testing it with >>>>> pthread_testcancel does not work. >>>>> >>>>> What is the trace of your test when run: >>>>> - on ARM >>>>> - with root thread priority inheritance, >>>>> - with USE_EXPLICIT_SCHED and USE_TEST_CANCEL, and CANCEL_TYPE set to >>>>> PTHREAD_CANCEL_DEFERRED >>>>> - posting a semaphore in ctrl_func before calling nanosleep, and waiting >>>>> for that semaphore in main before creating the calc_func thread. >>>> The calc_thread is not canceled and a segmentation fault happens. >>>> Canceling the calc_thread does *not* work if it's running in primrary >>>> mode, nor on ARM, nor on PowerPC. It does work when calc_thread does run >>>> in secondary mode, which happened with USE_EXPLICIT_SCHED not set. If >>>> you want do to some tests, I could send you my revised test program. >>>> My conclusion is that pthread_cancel can not be used to cancel busy >>>> realtime threads. I'm going to re-write the program using the native >>>> skin and rt_task_delete. >>> Yes, but what interests me is how it fails, that is seeing the trace of >>> your program. >> With pthread_cancel you do not see too much because the rt_printf >> messages do not get printed: > > As a temporary quirk, could you try, in rtdk, to install a handler for > SIGSEGV which flushes the print buffers ? OK. Hm, flushing the rt_print buffers before exit is what I'm actually looking for. Registering an cleanup handler would already be enough. But an active real-time task will also delay the exit(). Nevertheless, I tried with the native skin and it cancellation works fine with: rt_task_suspend(&calc_thread); rt_task_delete(&calc_thread); Can I do a task suspend with the Xenomai POSIX skin? Wolfgang.