From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4E760A16.8080907@domain.hid> Date: Sun, 18 Sep 2011 17:11:18 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4E6C927F.3070901@domain.hid> <4E6CC49C.1020403@domain.hid> <4E6CC5CC.5020204@domain.hid> <4E73AE00.3040002@domain.hid> <4E73B403.1060706@domain.hid> <1316354565.2169.20.camel@domain.hid> <4E760186.3040907@domain.hid> <1316358615.2169.21.camel@domain.hid> In-Reply-To: <1316358615.2169.21.camel@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigCC47EE2F746A60AEC6567D83" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-core] Policy switching and XNOTHER maintenance List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: xenomai-core This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigCC47EE2F746A60AEC6567D83 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 2011-09-18 17:10, Philippe Gerum wrote: > On Sun, 2011-09-18 at 16:34 +0200, Jan Kiszka wrote: >> On 2011-09-18 16:02, Philippe Gerum wrote: >>> On Fri, 2011-09-16 at 22:39 +0200, Gilles Chanteperdrix wrote: >>>> On 09/16/2011 10:13 PM, Gilles Chanteperdrix wrote: >>>>> On 09/11/2011 04:29 PM, Jan Kiszka wrote: >>>>>> On 2011-09-11 16:24, Gilles Chanteperdrix wrote: >>>>>>> On 09/11/2011 12:50 PM, Jan Kiszka wrote: >>>>>>>> Hi all, >>>>>>>> >>>>>>>> just looked into the hrescnt issue again, specifically the corne= r case >>>>>>>> of a shadow thread switching from real-time policy to SCHED_OTHE= R. >>>>>>> >>>>>>> Doing this while holding a mutex looks invalid. >>>>>> >>>>>> Looking at POSIX e.g., is there anything in the spec that makes th= is >>>>>> invalid? If the kernel preserves or established proper priority >>>>>> boosting, I do not see what could break in principle. >>>>>> >>>>>> It is nothing I would design into some app, but we should somehow = handle >>>>>> it (doc update or code adjustments). >>>>>> >>>>>>> If we do not do it, the current code is valid. >>>>>> >>>>>> Except for its dependency on XNOTHER which is not updated on RT->N= ORMAL >>>>>> transitions. >>>>> >>>>> The fact that this update did not take place made the code work. No= =20 >>>>> negative rescnt could happen with that code. >>>>> >>>>> Anyway, here is a patch to allow switching back from RT to NORMAL, = but=20 >>>>> send a SIGDEBUG to a thread attempting to release a mutex while its= =20 >>>>> counter is already 0. We end up avoiding a big chunk of code that w= ould=20 >>>>> have been useful for a really strange corner case. >>>>> >>>> >>>> Here comes version 2: >>>> diff --git a/include/nucleus/sched-idle.h b/include/nucleus/sched-id= le.h >>>> index 6399a17..417170f 100644 >>>> --- a/include/nucleus/sched-idle.h >>>> +++ b/include/nucleus/sched-idle.h >>>> @@ -39,6 +39,8 @@ extern struct xnsched_class xnsched_class_idle; >>>> static inline void __xnsched_idle_setparam(struct xnthread *thread,= >>>> const union xnsched_policy_param *p) >>>> { >>>> + if (xnthread_test_state(thread, XNSHADOW)) >>>> + xnthread_clear_state(thread, XNOTHER); >>>> thread->cprio =3D p->idle.prio; >>>> } >>>> =20 >>>> diff --git a/include/nucleus/sched-rt.h b/include/nucleus/sched-rt.h= >>>> index 71f655c..cc1cefa 100644 >>>> --- a/include/nucleus/sched-rt.h >>>> +++ b/include/nucleus/sched-rt.h >>>> @@ -86,6 +86,12 @@ static inline void __xnsched_rt_setparam(struct x= nthread *thread, >>>> const union xnsched_policy_param *p) >>>> { >>>> thread->cprio =3D p->rt.prio; >>>> + if (xnthread_test_state(thread, XNSHADOW)) { >>>> + if (thread->cprio) >>>> + xnthread_clear_state(thread, XNOTHER); >>>> + else >>>> + xnthread_set_state(thread, XNOTHER); >>>> + } >>>> } >>>> =20 >>>> static inline void __xnsched_rt_getparam(struct xnthread *thread, >>>> diff --git a/ksrc/nucleus/pod.c b/ksrc/nucleus/pod.c >>>> index 9a02e80..d19999f 100644 >>>> --- a/ksrc/nucleus/pod.c >>>> +++ b/ksrc/nucleus/pod.c >>>> @@ -1896,16 +1896,6 @@ int __xnpod_set_thread_schedparam(struct xnth= read *thread, >>>> xnsched_putback(thread); >>>> =20 >>>> #ifdef CONFIG_XENO_OPT_PERVASIVE >>>> - /* >>>> - * A non-real-time shadow may upgrade to real-time FIFO >>>> - * scheduling, but the latter may never downgrade to >>>> - * SCHED_NORMAL Xenomai-wise. In the valid case, we clear >>>> - * XNOTHER to reflect the change. Note that we keep handling >>>> - * non real-time shadow specifics in higher code layers, not >>>> - * to pollute the core scheduler with peculiarities. >>>> - */ >>>> - if (sched_class =3D=3D &xnsched_class_rt && sched_param->rt.prio >= 0) >>>> - xnthread_clear_state(thread, XNOTHER); >>>> if (propagate) { >>>> if (xnthread_test_state(thread, XNRELAX)) >>>> xnshadow_renice(thread); >>>> diff --git a/ksrc/nucleus/sched-sporadic.c b/ksrc/nucleus/sched-spor= adic.c >>>> index fd37c21..ffc9bab 100644 >>>> --- a/ksrc/nucleus/sched-sporadic.c >>>> +++ b/ksrc/nucleus/sched-sporadic.c >>>> @@ -258,6 +258,8 @@ static void xnsched_sporadic_setparam(struct xnt= hread *thread, >>>> } >>>> } >>>> =20 >>>> + if (xnthread_test_state(thread, XNSHADOW)) >>>> + xnthread_clear_state(thread, XNOTHER); >>>> thread->cprio =3D p->pss.current_prio; >>>> } >>>> =20 >>>> diff --git a/ksrc/nucleus/sched-tp.c b/ksrc/nucleus/sched-tp.c >>>> index 43a548e..a2af1d3 100644 >>>> --- a/ksrc/nucleus/sched-tp.c >>>> +++ b/ksrc/nucleus/sched-tp.c >>>> @@ -100,6 +100,8 @@ static void xnsched_tp_setparam(struct xnthread = *thread, >>>> { >>>> struct xnsched *sched =3D thread->sched; >>>> =20 >>>> + if (xnthread_test_state(thread, XNSHADOW)) >>>> + xnthread_clear_state(thread, XNOTHER); >>>> thread->tps =3D &sched->tp.partitions[p->tp.ptid]; >>>> thread->cprio =3D p->tp.prio; >>>> } >>>> diff --git a/ksrc/nucleus/synch.c b/ksrc/nucleus/synch.c >>>> index b956e46..47bc0c5 100644 >>>> --- a/ksrc/nucleus/synch.c >>>> +++ b/ksrc/nucleus/synch.c >>>> @@ -684,9 +684,13 @@ xnsynch_release_thread(struct xnsynch *synch, s= truct xnthread *lastowner) >>>> =20 >>>> XENO_BUGON(NUCLEUS, !testbits(synch->status, XNSYNCH_OWNER)); >>>> =20 >>>> - if (xnthread_test_state(lastowner, XNOTHER)) >>>> - xnthread_dec_rescnt(lastowner); >>>> - XENO_BUGON(NUCLEUS, xnthread_get_rescnt(lastowner) < 0); >>>> + if (xnthread_test_state(lastowner, XNOTHER)) { >>>> + if (xnthread_get_rescnt(lastowner) =3D=3D 0) >>>> + xnshadow_send_sig(lastowner, SIGDEBUG, >>>> + SIGDEBUG_MIGRATE_PRIOINV, 1); >>>> + else >>>> + xnthread_dec_rescnt(lastowner); >>>> + } >>>> lastownerh =3D xnthread_handle(lastowner); >>>> =20 >>>> if (use_fastlock && >>>> >>>> >>>> >>> >>> Agreed, the logic of this patch sounds right. Switching from -rt to -= nrt >>> while holding a -rt mutex is pathological behavior. We don't have to >>> support apps implementing voluntary priority inversion. >>> >> >> No concerns either. >> >> Now we just need >> >> diff --git a/ksrc/nucleus/shadow.c b/ksrc/nucleus/shadow.c >> index 21cc191..27bc829 100644 >> --- a/ksrc/nucleus/shadow.c >> +++ b/ksrc/nucleus/shadow.c >> @@ -2756,9 +2756,12 @@ static inline void do_setsched_event(struct tas= k_struct *p, int priority) >> union xnsched_policy_param param; >> struct xnsched *sched; >> =20 >> - if (!thread || p->policy !=3D SCHED_FIFO) >> + if (!thread) >> return; >> =20 >> + if (p->policy =3D=3D SCHED_FIFO) > ^^ > inverted? Of course. Jan --------------enigCC47EE2F746A60AEC6567D83 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk52ChYACgkQitSsb3rl5xQrbACcCgxjkZbwUJj5a5CTZ6r2WqJj fQsAoJsyRnFbiTEt7mp7RbGFSQbbFMyA =B/ku -----END PGP SIGNATURE----- --------------enigCC47EE2F746A60AEC6567D83--