Sebastian Smolorz wrote: > Jan Kiszka wrote: >> Sebastian Smolorz wrote: >>> Jan Kiszka wrote: >>>> Sebastian Smolorz wrote: >>>>> Hi, >>>>> >>>>> we all know that the latency test should not be run with a period of >>>>> 100 us because it easily gets locked up. The attached trace illustrates >>>>> this problem in detail. It shows that a timer interrupt needs about 50 >>>>> us to be processed. Furthermore, there is not enough time between two >>>>> timer interrupts for the latency task to get all its work done. >>>>> >>>>> The current I-pipe tracer patch for ARM is available at >>>>> http://opensource.emlix.com/ipipe-s3c24xx/download/ipipe-tracer-arm.pat >>>>> ch _v4 >>>>> >>>>> Comments welcome. >>>> Something is still broken, given all those "N"s in Delay column. Is >>>> there something like NMI at all on your board? >>> There isn't AFAIK. What could be the reason for all this noise? Recursive >>> spin-locking? >> Yes. If those Ns aren't false positive in the sense that >> IPIPE_TFLG_NMI_HIT is set accidentally, __ipipe_trace is re-entered >> while IPIPE_TFLG_NMI_LOCK is still set. > > Interesting: If I disable CONFIG_IPIPE_TRACE_MCOUNT the "Noise" doesn't > appear > at all.
Sounds like some function that __ipipe_trace calls is instrumented, thus the recursion. Could be something trivial like memcpy (if that happens to be uninlined here). You may want to check the disassembly... :) Jan
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