From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <50EC8B26.5050800@web.de> Date: Tue, 08 Jan 2013 22:09:58 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <50ebff2e488690.18102992@wp.pl> <50EC76E9.30002@xenomai.org> <50EC8A6D.2060702@web.de> In-Reply-To: <50EC8A6D.2060702@web.de> 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 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 lik= e 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 surpris= ing is that the replacing TM_NONBLOCK with TM_INFINITE, in one before last = line, do magic and suppress signal generation. Furthermore, there is no cal= l to 'rt_task_set_mode(0, T_WARNSW, NULL);' so why = >>> signal is generated? If we enable T_WARNSW in the thread, SIGXCPU is ge= nerated 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. > = BTW, signaling this inconsistent state via SIGDEBUG and no further indication what went wrong and what is different to "normal" SIGDEBUG_MIGRATE_PRIOINV is not a good idea. We should issue a kernel log message or, better, use a different, specific reason code. Jan -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 261 bytes Desc: OpenPGP digital signature URL: