Jan Kiszka wrote: > Philippe Gerum wrote: >> I've toyed a bit to find a generic approach for the nucleus to regain >> complete control over a userland application running in a syscall-less >> loop. >> >> The original issue was about recovering gracefully from a runaway >> situation detected by the nucleus watchdog, where a thread would spin in >> primary mode without issuing any syscall, but this would also apply for >> real-time signals pending for such a thread. Currently, Xenomai rt >> signals cannot preempt syscall-less code running in primary mode either. >> >> The major difference between the previous approaches we discussed about >> and this one, is the fact that we now force the runaway thread to run a >> piece of valid code that calls into the nucleus. We do not force the >> thread to run faulty code or at a faulty address anymore. Therefore, we >> can reuse this feature to improve the rt signal management, without >> having to forge yet-another signal stack frame for this. >> >> The code introduced only fixes the watchdog related issue, but also does >> some groundwork for enhancing the rt signal support later. The >> implementation details can be found here: >> http://git.xenomai.org/?p=xenomai-rpm.git;a=commit;h=4cf21a2ae58354819da6475ae869b96c2defda0c >> >> The current mayday support is only available for powerpc and x86 for >> now, more will come in the next days. To have it enabled, you have to >> upgrade your I-pipe patch to 2.6.32.15-2.7-00 or 2.6.34-2.7-00 for x86, >> 2.6.33.5-2.10-01 or 2.6.34-2.10-00 for powerpc. That feature relies on a >> new interface available from those latest patches. >> >> The current implementation does not break the 2.5.x ABI on purpose, so >> we could merge it into the stable branch. >> >> We definitely need user feedback on this. Typically, does arming the >> nucleus watchdog with that patch support in, properly recovers from your >> favorite "get me out of here" situation? TIA, >> >> You can pull this stuff from >> git://git.xenomai.org/xenomai-rpm.git, queue/mayday branch. >> > > I've retested the feature as it's now in master, and it has one > remaining problem: If you run the cpu hog under gdb control and try to > break out of the while(1) loop, this doesn't work before the watchdog > expired - of course. But if you send the break before the expiry (or hit > a breakpoint), something goes wrong. The Xenomai task continues to spin, > and there is no chance to kill its process (only gdb). > > # cat /proc/xenomai/sched > CPU PID CLASS PRI TIMEOUT TIMEBASE STAT NAME > 0 0 idle -1 - master RR ROOT/0 > 1 0 idle -1 - master R ROOT/1 > 0 6120 rt 99 - master Tt cpu-hog > # cat /proc/xenomai/stat > CPU PID MSW CSW PF STAT %CPU NAME > 0 0 0 0 0 00500088 0.0 ROOT/0 > 1 0 0 0 0 00500080 99.7 ROOT/1 > 0 6120 0 1 0 00342180 100.0 cpu-hog > 0 0 0 21005 0 00000000 0.0 IRQ3340: [timer] > 1 0 0 35887 0 00000000 0.3 IRQ3340: [timer] >
Fixable by this tiny change: diff --git a/ksrc/nucleus/sched.c b/ksrc/nucleus/sched.c index 5242d9f..04a344e 100644 --- a/ksrc/nucleus/sched.c +++ b/ksrc/nucleus/sched.c @@ -175,7 +175,8 @@ void xnsched_init(struct xnsched *sched, int cpu) xnthread_name(&sched->rootcb)); #ifdef CONFIG_XENO_OPT_WATCHDOG - xntimer_init(&sched->wdtimer, &nktbase, xnsched_watchdog_handler); + xntimer_init_noblock(&sched->wdtimer, &nktbase, + xnsched_watchdog_handler); xntimer_set_name(&sched->wdtimer, "[watchdog]"); xntimer_set_priority(&sched->wdtimer, XNTIMER_LOPRIO); xntimer_set_sched(&sched->wdtimer, sched); I.e. the watchdog timer should not be stopped by any ongoing debug session of a Xenomai app. Will queue this for upstream. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core