Philippe Gerum wrote: > On Mon, 2009-11-09 at 19:50 +0100, Jan Kiszka wrote: >> Gilles Chanteperdrix wrote: >>> Jan Kiszka wrote: >>>> Gilles Chanteperdrix wrote: >>>>> Jan Kiszka wrote: >>>>>> Hi Philippe, >>>>>> >>>>>> just noticed: The __ipipe_check_percpu_access of __ipipe_get_cpu_var, >>>>>> added in 2.6.29, makes ipipe_test_pipeline_from unusable for debugging >>>>>> purposes. It now triggers a false positive warning if the caller did not >>>>>> disabled interrupts or stalled its pipeline. One such user under Xenomai >>>>>> is rthal_local_irq_disabled, and that is used to check RTDM driver >>>>>> handlers /wrt leaking IRQ masks. >>>>> It does not look like a false positive. If the task issuing the call to >>>>> rthal_local_irq_disabled function was migrated at the wrong time, it >>>>> could check the stall flag on the wrong cpu. >>>> Unless you want to test the migration logic itself, a plain task in >>>> whatever domain should never see a CPU-depend rthal_local_irq_disabled - >>>> migration should never alter the context in this respect. >>>> > > A plain task over the root domain which is subject to a migration may > end up testing the stall bit on the wrong (dest) CPU, which may execute > a different domain than the one running on the source CPU. As soon as
Yeah, makes sense now (with source and dest swapped, though). > the domain is not a context invariant, you do have a serious issue > coming up. So this does matter a lot, as the bug fixed some time ago in > ipipe_check_context() showed. > >>>>> So, it looks like >>>>> rthal_local_irq_disabled should be fixed to turn off irqs during the >>>>> check. >>>>> >>>> Would work, but would also be more heavy-weighted then needed. >>> If it is debug stuff, does the heavy-weight matter that much? >>> >> Actually, I'm no longer sure that a preemption check for >> ipipe_stall_pipeline_from makes sense at all. Am I missing some case? >> > > Same as above. Albeit there may not be forced CPU migration over the > Xenomai domain, this is perfectly possible on the root one. OK, will fix the checks in RTDM then. Jan
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