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. -- Philippe. _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
