On 2013-01-12 19:43, Gilles Chanteperdrix wrote: > On 01/09/2013 02:30 PM, Jan Kiszka wrote: > >> On 2013-01-08 22:06, Jan Kiszka wrote: >>> On 2013-01-08 20:43, Gilles Chanteperdrix wrote: >>>> On 01/08/2013 12:12 PM, Mariusz Janiak wrote: >>>> >>>>> Hi GIlles, >>>>> >>>>> As you suggested, I have prepared simple test case that demonstrate how >>>>> Xenomai is utilized by OROCOS. This test case behaves exactly the same >>>>> like helloword example. Scheduler is chosen before any mutex are >>>>> processed, so in my opinion it is not the case which you defined. What is >>>>> really surprising is that the replacing TM_NONBLOCK with TM_INFINITE, in >>>>> one before last line, do magic and suppress signal generation. >>>>> Furthermore, there is no call to 'rt_task_set_mode(0, T_WARNSW, NULL);' >>>>> so why >>>>> signal is generated? If we enable T_WARNSW in the thread, SIGXCPU is >>>>> generated when mutex is locked first time in the thread. >>>> >>>> >>>> I guess the test could be simpler, simply: >>>> >>>> rt_mutex_acquire >>>> rt_task_create >>>> rt_mutex_release >>>> rt_mutex_acquire >>>> rt_mutex_release >>>> >>>> Anyway, calling rt_task_create while holding a real-time mutex is itself >>>> a priority inversion: any thread in primary mode waiting for the mutex >>>> will now have to wait for task running in secondary mode, so may be >>>> block during an unbounded amount of time. So, using a real-time mutex >>>> for this is completely useless you should be using a glibc >>>> pthread_mutex_t. If compiling for the posix skin, use >>>> __real_pthread_mutex_lock. >>>> >>>> Now, how this can cause the issue you observe remains to be understood, >>>> and probably requires a fix. >>> >>> OK, second try: We do not update the new owner's hrescnt if we acquire a >>> mutex via trylock. This applies both to rt_mutex_acquire_inner and >>> pthread_mutex_trylock. Probably, this should be done in the >>> corresponding syscall wrapper as both services are also used for the >>> in-kernel API. >> >> Here is the corresponding patch: > >> http://www.xenomai.org/pipermail/xenomai-git/2013-January/000336.html > > Ok, so, if I understand correctly, the whole orocos testcase boils down to: > trylock > unlock > > We should move the incrementation of the resource counter to > xnsynch_fast_acquire. We will be left with only two places to patch: the > native and posix trylock in the !FASTSYNCH case.
xnsynch_fast_acquire is shared with user space code and therefore references no kernel types. Jan -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 261 bytes Desc: OpenPGP digital signature URL: <http://www.xenomai.org/pipermail/xenomai/attachments/20130113/610ec0d2/attachment.pgp> _______________________________________________ Xenomai mailing list [email protected] http://www.xenomai.org/mailman/listinfo/xenomai
