Re: performance monitor exceptions

benh@kernel.crashing.org wrote:

 - I don't know how the perf. mon stuff works, but couldn't you
enter a condition were the CPU is continuously sending your the
pef monitor exception until you clear something else ?

No, in a performance monitor exception, PMXE (PM exception enable)
is cleared in MMCR0, and I need to set it explicitly to get another
exception. The only performance event source that's enabled is the
one using the timer base, so this gives me exceptions at 200 Hz,
more if I want.

 - I encountered a problem with the TAU stuff and the 7400 where
the CPU could actually get mixed up when getting both a normal
interrupt and a TAU exception and scew up itself (by taking both
exceptions and screwing up SRR0/1)

Bingo ! That seems to be the one:

http://www.mot.co.jp/SPS/html/lit/pdf/mpc7410pns_rev0.pdf

  #5:
  Description: Consecutive Performance Monitor, Decrementer,
  or Thermal Management Interrupts may become non-recoverable.

  Work-Around: Avoid enabling any combination of
  Performance Monitor, Decrementer, or Thermal Management
  Interrupts at the same time.

Hmm, working around this will be tricky ...

Thanks a lot !

- Werner

--
  _________________________________________________________________________
 / Werner Almesberger, Lausanne, CH                    wa@almesberger.net /
/_http://icawww.epfl.ch/almesberger/_____________________________________/

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