[PATCH] perf/core / arm_pmu: special-case hetereogeneous CPUs

[Mark Rutland]

On Mon, Apr 25, 2016 at 09:03:34PM +0200, Peter Zijlstra wrote:
> On Mon, Apr 25, 2016 at 06:58:37PM +0100, Mark Rutland wrote:
> > Hi,
> > 
> > When booting an arm64 defconfig linux-next (next-20160422) on an ARM
> > Juno system, I hit a WARN_ON_ONCE in perf_pmu_register (see backtrace at
> > the end of this email).
> > 
> > This was introduced by commit 26657848502b7847 ("perf/core: Verify we
> > have a single perf_hw_context PMU") where we forcefully prevent multiple
> > PMUs from sharing perf_hw_context (with a warning), and force additional
> > PMUs to use perf_invalid_context.

> > Are you happy to revert 26657848502b787 for the timebeing? Or to somehow
> > predicate the check such that it doesn't adversely affect those HW PMUs?
> 
> I'm happy with a chicken bit for now, its already found two real issues,
> so I'd like to keep it.

Ok, how about the below? (based on next-20160422).

It looks like 26657848502b7847 was on a stable branch, so I guess we
can't fold this in. It probably makes sense for this to go the same path
as 26657848502b7847, assuming people are happy with that and there are
no conflicts.

Mark.

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