Re: [PATCH] oprofile, x86: Fix race in nmi handler while starting

From: Ingo Molnar
Date: Fri Jun 17 2011 - 04:06:43 EST

* Robert Richter <robert.richter@xxxxxxx> wrote:

> On 09.06.11 03:18:54, Ingo Molnar wrote:
> >
> > * Robert Richter <robert.richter@xxxxxxx> wrote:
> >
> > > In some rare cases, nmis are generated immediately after the
> > > nmi handler of the cpu was started. This causes the counter not
> > > to be enabled. Before enabling the nmi handlers we need to set
> > > variable ctr_running first and make sure its value is written
> > > to memory.
> > >
> > > Also, the patch makes all existing barriers a memory barrier
> > > instead of a compiler barrier only.
> >
> > Could we *PLEASE* just do the obvious and turn oprofile into a
> > perf user on x86 too, like ARM already does? Two years down the
> > line and there's zero progress in that area. We want to obsolete
> > the Oprofile PMU bits on x86, the infrastructure duplication
> > causes non-trivial problems like this one.
> Ingo,
> I would rather prefer to spend the effort to add full pmu support
> to perf. AMD features missing are still IBS and nb performance
> counters for family 15h. The oprofile kernel driver would become
> obsolete at all with a new daemon using the perf syscall interface.

Agreed - i just don't see *any* progress on the IBS front: more time
seems to be spent on fixing and sometimes even extending oprofile
than on any IBS work.


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