linux-kernel - Re: [PATCH 22/24] i386: add TRACE_IRQS

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Date:	Mon, 12 Jan 2009 21:50:50 +0100
From:	"Alexander van Heukelum" <heukelum@...tmail.fm>
To:	"Peter Zijlstra" <peterz@...radead.org>,
	"Ingo Molnar" <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, "Andi Kleen" <ak@...e.de>,
	"Dhaval Giani" <dhaval@...ux.vnet.ibm.com>
Subject: Re: [PATCH 22/24] i386: add TRACE_IRQS_OFF for the nmi


On Mon, 12 Jan 2009 19:43:35 +0100, "Peter Zijlstra"
<peterz@...radead.org> said:
> On Mon, 2009-01-12 at 19:39 +0100, Ingo Molnar wrote:
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > On Tue, 2008-09-09 at 21:56 +0200, heukelum@...tmail.fm wrote:
> > > > From: Alexander van Heukelum <heukelum@...tmail.fm>
> > > > 
> > > > At this point interrupts are off, so let's inform the tracing
> > > > code of that fact before calling into C.
> > > 
> > > Sorry but this is an obvious dud, lockdep (and thus the irq state
> > > tracer) aren't nmi safe.
> > > 
> > > Ingo, please revert, as people are already seeing lockdep warnings due
> > > to this.
> > 
> > done - reverted it in tip/x86/urgent, see the commit below. Is that all 
> > that we need, wasnt there a 64-bit side done too?
> 
> I had a _very_ quick peek but couldn't fine one, Alexander, does your
> memory go back that far? :-)

Git helped a bit, I must admit. The 64-bit version does not include
TRACE_IRQS_ON/TRACE_IRQS_OFF in the nmi handler. The comment above
"ENTRY(paranoid_exit)" in entry_64.S should be updated, though. That
code is not used for NMIs.

The revert is obviously the correct thing to do, but a comment would
not hurt here either.

Greetings,
    Alexander
-- 
  Alexander van Heukelum
  heukelum@...tmail.fm

-- 
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