Re: [Xenomai-core] How to cancel a Xenomai POSIX thread

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Gilles Chanteperdrix wrote:
 > Wolfgang Grandegger wrote:
 >  > Hi Gilles,
 >  > 
 >  > Gilles Chanteperdrix wrote:
 >  > > On Dec 6, 2007 3:05 PM, Wolfgang Grandegger <wg@domain.hid> wrote:
 >  > >> Gilles Chanteperdrix wrote:
 >  > >>> On Dec 6, 2007 2:28 PM, Gilles Chanteperdrix
 >  > >>> <gilles.chanteperdrix@xenomai.org> wrote:
 >  > >>>> On Dec 6, 2007 2:24 PM, Wolfgang Grandegger <wg@domain.hid> wrote:
 >  > >>>>> Gilles Chanteperdrix wrote:
 >  > >>>>>> On Dec 6, 2007 1:31 PM, Wolfgang Grandegger <wg@domain.hid> 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.

-- 


					    Gilles Chanteperdrix.