From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <50EC8A6D.2060702@web.de> Date: Tue, 08 Jan 2013 22:06:53 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <50ebff2e488690.18102992@wp.pl> <50EC76E9.30002@xenomai.org> In-Reply-To: <50EC76E9.30002@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 2013-01-08 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 surprisi= ng is that the replacing TM_NONBLOCK with TM_INFINITE, in one before last l= ine, 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 gen= erated 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. Jan -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 261 bytes Desc: OpenPGP digital signature URL: