Re: [PATCH][2.6.9-rc2-mm3] perfctr ppc32 preliminary interruptsupport

[Benjamin Herrenschmidt]

> Tested on an MPC7455 (G4-type chip). The patch applies cleanly
> to and compiles ok in 2.6.9-rc2-mm3, but 2.6.9-rc2-mm3 has
> other problems on PPC32 so I tested it with 2.6.9-rc2 vanilla.

Be careful that some G4's have a bug which can cause a
perf monitor interrupt to crash your kernel :( Basically, the
problem is if any of TAU or PerfMon interrupt happens at the
same time as a DEC interrupt, some revs of the CPU can get
confused and lose the previous exception state.

Check out the erratas, but it may be worth adding a cputable
feature bit entry to note which models have useable interrupt
and which don't.



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