From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <475CEA44.9060007@domain.hid> Date: Mon, 10 Dec 2007 08:27:00 +0100 From: Wolfgang Grandegger MIME-Version: 1.0 References: <4757EBAE.4050608@domain.hid> <2ff1a98a0712060513g3b056866x883691498daf00e1@domain.hid> <4757F811.70905@domain.hid> <2ff1a98a0712060528y13159abdwb83617a8744b3735@domain.hid> <2ff1a98a0712060544x6e1e8c11q52e9417fb096e4b7@domain.hid> <475801AA.3060300@domain.hid> <2ff1a98a0712060621k436f32b7sc1d1cfe53bea8f18@domain.hid> <475952CD.3020003@domain.hid> <18265.47545.897637.377869@domain.hid> <18265.50385.343346.558000@domain.hid> <475C6454.2090002@domain.hid> <18268.29130.406826.933528@domain.hid> In-Reply-To: <18268.29130.406826.933528@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] How to cancel a Xenomai POSIX thread List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: xenomai-core Gilles Chanteperdrix wrote: > Wolfgang Grandegger wrote: > > Gilles Chanteperdrix wrote: > > > Gilles Chanteperdrix wrote: > > > > Wolfgang Grandegger wrote: > > > > > Hi Gilles, > > > > > > > > > > Gilles Chanteperdrix wrote: > > > > > > On Dec 6, 2007 3:05 PM, Wolfgang Grandegger wrote: > > > > > >> Gilles Chanteperdrix wrote: > > > > > >>> On Dec 6, 2007 2:28 PM, Gilles Chanteperdrix > > > > > >>> wrote: > > > > > >>>> On Dec 6, 2007 2:24 PM, Wolfgang Grandegger wrote: > > > > > >>>>> Gilles Chanteperdrix wrote: > > > > > >>>>>> On Dec 6, 2007 1:31 PM, Wolfgang Grandegger wrote: > > > > > >>>>>>> Hello, > > > > > >>>>>>> > > > > > >>>>>>> how do I cancel or delete a Xenomai POSIX thread running in primary > > > > > >>>>>>> context from a higher priority thread? IIUC, pthread_kill() can only be > > > > > >>>>>>> used in secondary context. I tried pthread_cancel(), but it only works > > > > > >>>>>>> when hitting a cancelation point, e.g. pthread_testcancel(). Setting > > > > > >>>>>>> pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS) did not help. Is > > > > > >>>>>>> there a code snippet or even an example program showing how to cancel a > > > > > >>>>>>> pthread in primary context? > > > > > >>>>>> pthread_kill or pthread_cancel should result in sending a signal to > > > > > >>>>>> the target thread, so should cause this thread to switch to secondary > > > > > >>>>>> mode to handle it. If you want to wait for the target thread to be > > > > > >>>>>> canceled, you should use pthread_cancel and pthread_join. > > > > > >>>>> There is no way to cancel a pthread in primary mode from another pthread? > > > > > >>>> No. You always need secondary mode to effectively delete a thread. The > > > > > >>>> same goes for the native skin. > > > > > >>> Ok. I understand what you mean. You want pthread_cancel not to leave > > > > > >>> primary mode. This can easily be done by causing pthread_cancel to use > > > > > >>> the kernel-space real-time pthread_cancel service. This should work > > > > > >>> with no further modification. > > > > > >> I want to cancel/delete a task running in primary mode, e.g. > > > > > >> > > > > > >> void* work_task(void* dummy) > > > > > >> { > > > > > >> int count = 0; > > > > > >> while (1) > > > > > >> count++; > > > > > >> } > > > > > >> > > > > > >> from the outside (= another higher priority task). How can I use the > > > > > >> kernel-space real-time pthread_cancel service? My POSIX app is runs in > > > > > >> user-land. > > > > > > > > > > > > I was thinking about adding a pthread_cancel syscall that would have > > > > > > triggered the kernel-space pthread_cancel. But this will not work: > > > > > > user-space cleanup handlers would no longer get executed. However, > > > > > > this can work for pthread_kill. Here is a patch which adds the > > > > > > pthread_kill syscall. > > > > > > > > > > Great, thanks a lot. This seems to work but I'm now fiddling with proper > > > > > cleanup and exit. I have attached my small test program. It behaves > > > > > somehow strange, at least to me: > > > > > > > > > > - I see task period overruns when the low prio task is started. I > > > > > suspect some switch to secondary mode in init_task(). > > > > > > > > > > - The program/system hangs after the listed messages: > > > > > > > > > > # ./kill_pthread > > > > > Starting high_prio_task > > > > > Killed low_prio task: count=3813129, overruns=0 > > > > > > > > > > Any idea what I'm doing wrong? > > > > > > > > > > This is with Linux 2.4.25 and Xenomai 2.3.x on a MPC5200 board. > > > > > > > > Your test runs fine with Xenomai trunk (on ARM). I will now try with > > > > current state of the v2.3.x branch. > > > > > > Works with v2.3.x too. > > > > I re-activated my test PC running Linux 2.6.20.21. with Xenomai 2.3.x. > > There the program runs fine _without_ your pthread_kill patch. For some > > reason the low_prio_task() is running in secondary mode (do you know > > why? Is there a function to check the mode?). I added > > > > struct sched_param param = { .sched_priority = LOW_PRIO }; > > pthread_setschedparam(pthread_self(), SCHED_FIFO, ¶m); > > > > to the head of that function and then I get: > > > > ./kill_pthread > > Starting high_prio_task > > BUG: NMI Watchdog detected LOCKUP > > Killed low_prio task: count=1588495996, overruns=0 > > Exiting main > > > > I have attached the corresponding oops in case it's of interest. > > Unfortunately, with your patch and adding the function > > __real_pthread_kill() to wrappers.c, the behavior is the same. I'm going > > to repeat the tests with Xenomai trunk tomorrow. > > The oops is due to the NMI watchdog calling some linux domain functions > over Xenomai domain. You should probably use Xenomai watchdog instead. OK, the Xenomai watchdog might be another possibility to kill a pthread blocking the system. > As for the reason why the watchdog triggers: are you sure you are > running the kernel recompiled after having applied the patch? Yes, because: # grep pthread_kill System.map c015af9e T pthread_kill c015f4e6 t __pthread_kill c0390650 r __ksymtab_pthread_kill c03968b8 r __kcrctab_pthread_kill c039ce83 r __kstrtab_pthread_kill But I will double-check again. Wolfgang.