linux-kernel - Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

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Message-ID: <20100824162252.GB5723@lenovo>
Date:	Tue, 24 Aug 2010 20:22:52 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Don Zickus <dzickus@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Robert Richter <robert.richter@....com>,
	Lin Ming <ming.m.lin@...el.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running
	perfctrs

On Mon, Aug 23, 2010 at 10:53:39AM +0200, Ingo Molnar wrote:
> 
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
> > 
> > * Don Zickus <dzickus@...hat.com> wrote:
> > 
> > > I'll test tip later today to see if I can reproduce it.
> > > 
> > > Cheers,
> > > Don
> > > 
> > > Ingo Molnar <mingo@...e.hu> wrote:
> > > 
> > > >
> > > >it's not working so well, i'm getting:
> > > >
> > > > Uhhuh. NMI received for unknown reason 00 on CPU 9.
> > > > Do you have a strange power saving mode enabled?
> > > > Dazed and confused, but trying to continue
> > > >
> > > >on a nehalem box, after a perf top and perf stat run.
> > 
> > FYI, it does not trigger on an AMD box.
> 
> Ok, to not hold up the perf/urgent flow i zapped these two commits for 
> the time being:
> 
>  4a31beb: perf, x86: Fix handle_irq return values
>  8e3e42b: perf, x86: Try to handle unknown nmis with an enabled PMU
> 
> We can apply them if they take a form that dont introduce a different 
> kind of (and more visible) regression.
> 
> Thanks,
> 
> 	Ingo
> 

Btw, guys, I fail to see how new nmi_watchdog work, we have
default_do_nmi
  if (!(reason & 0xc0)) {
    if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT) == == NOTIFY_STOP)
      return
    if (nmi_watchdog_tick(regs, reason))
      return

but perf_event_nmi_handler returns NOTIFY_STOP when watchdog is perf event
and nmi_watchdog_tick _never_ called, or (most probably) I miss something?

	-- Cyrill
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