From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <50F2A8B9.1040103@web.de> Date: Sun, 13 Jan 2013 13:29:45 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <50ebff2e488690.18102992@wp.pl> <50EC76E9.30002@xenomai.org> <50EC8A6D.2060702@web.de> <50ED70F0.8020608@siemens.com> <50F1AEDC.3070306@xenomai.org> In-Reply-To: <50F1AEDC.3070306@xenomai.org> Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: Re: [Xenomai] SIGXCPU with rt_mutex_release List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: Xenomai 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 h= ow Xenomai is utilized by OROCOS. This test case behaves exactly the same l= ike 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 surpr= ising is that the replacing TM_NONBLOCK with TM_INFINITE, in one before las= t line, do magic and suppress signal generation. Furthermore, there is no c= all 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 itse= lf >>>> 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 t= o: > 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: