On Thu, 07 Apr 2011, Benjamin Herrenschmidt wrote: > > > > Doesn't that mean that power_pmu_read() can only ever increase the value > > > of > > > the perf_event and so will essentially -stop- once the counter rolls over > > > ? > > > > > > Similar comments every where you do this type of comparison. > > > > > > Cheers, > > > Ben. > > > > Sorry for the nag, but am I missing something about the way the register and > > the previous values are reset in the overflow interrupt handler? > > Well, not all counters get interrupts right ? Some counters are just > free running... I'm not sure when that power_pmu_read() function is > actually used by the core, I'm not that familiar with perf, but I'd say > better safe than sorry. When comparing counter values, doing in a way > that is generally safe vs. wraparounds. Eventually do a helper for that. > > Cheers, > Ben.
I am honestly not sure, I was under the assumption that all counters would generate an interrupt if they overflowed. I do not have the hardware docs to prove this, so I will have a V3 that (I think/hope) addresses your concerns out momentarily. Eric
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