Subject: Re: [PATCH][2.6.9-rc2-mm3] perfctr ppc32 preliminary interrupt
	support
From: Albert Cahalan <albert@users.sf.net>
To: linux-kernel mailing list <linux-kernel@vger.kernel.org>
Cc: mikpe@csd.uu.se, benh@kernel.crashing.org
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Date: 27 Sep 2004 16:05:31 -0400
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Benjamin Herrenschmidt writes:

> 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.

Instead of excluding all these CPUs, simply put the
clock tick on the PerfMon interrupt. There's a bit-flip
that'll go at about 4 kHz on a system with a 100 MHz bus.
That should do. One need not change HZ; the interrupt
can be ignored whenever the timebase hasn't advanced
enough to require another clock tick.


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