On 06/18/2011 12:21 PM, Jan Kiszka wrote: > On 2011-06-17 20:55, Gilles Chanteperdrix wrote: >> On 06/17/2011 07:03 PM, Jan Kiszka wrote: >>> On 2011-06-17 18:53, Gilles Chanteperdrix wrote: >>>> On 06/17/2011 04:38 PM, GIT version control wrote: >>>>> Module: xenomai-jki >>>>> Branch: for-upstream >>>>> Commit: 7203b1a66ca0825d5bcda1c3abab9ca048177914 >>>>> URL: >>>>> http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=7203b1a66ca0825d5bcda1c3abab9ca048177914 >>>>> >>>>> Author: Jan Kiszka <jan.kis...@siemens.com> >>>>> Date: Fri Jun 17 09:46:19 2011 +0200 >>>>> >>>>> nucleus: Fix interrupt handler tails >>>>> >>>>> Our current interrupt handlers assume that they leave over the same task >>>>> and CPU they entered. But commit f6af9b831c broke this assumption: >>>>> xnpod_schedule invoked from the handler tail can now actually trigger a >>>>> domain migration, and that can also include a CPU migration. This causes >>>>> subtle corruptions as invalid xnstat_exectime_t objects may be restored >>>>> and - even worse - we may improperly flush XNHTICK of the old CPU, >>>>> leaving Linux timer-wise dead there (as happened to us). >>>>> >>>>> Fix this by moving XNHTICK replay and exectime accounting before the >>>>> scheduling point. Note that this introduces a tiny imprecision in the >>>>> accounting. >>>> >>>> I am not sure I understand why moving the XNHTICK replay is needed: if >>>> we switch to secondary mode, the HTICK is handled by xnpod_schedule >>>> anyway, or am I missing something? >>> >>> The replay can work on an invalid sched (after CPU migration in >>> secondary mode). We could reload the sched, but just moving the replay >>> is simpler. >> >> But does it not remove the purpose of this delayed replay? > > Hmm, yes, in the corner case of coalesced timed RT task wakeup and host > tick over a root thread. Well, then we actually have to reload sched and > keep the ordering to catch that as well. > >> >> Note that if you want to reload the sched, you also have to shut >> interrupts off, because upon return from xnpod_schedule after migration, >> interrupts are on. > > That would be another severe bug if we left an interrupt handler with > hard IRQs enabled - the interrupt tail code of ipipe would break. > > Fortunately, only xnpod_suspend_thread re-enables IRQs and returns. > xnpod_schedule also re-enables but then terminates the context (in > xnshadow_exit). So we are safe.
I do not think we are, at least on platforms where context switches happen with irqs on. -- Gilles. _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core