linux-kernel - Re: [PATCH] tracing/irqtrace: only call trace_hardirqs

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Message-ID: <20180501160059.6df6aae4@gandalf.local.home>
Date:   Tue, 1 May 2018 16:00:59 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/irqtrace: only call trace_hardirqs_on/off when
 state changes

On Tue, 1 May 2018 21:48:38 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> On Tue, May 01, 2018 at 03:38:40PM -0400, Steven Rostedt wrote:
> > On Tue, 1 May 2018 21:19:51 +0200
> > Peter Zijlstra <peterz@...radead.org> wrote:  
> 
> > > Now, lockdep only minimally tracks these otherwise redundant operations;
> > > see redundant_hardirqs_{on,off} counters, and loosing that doesn't seen
> > > like a big issue.
> > > 
> > > But I'm confused how this helps track superfluous things, it looks like
> > > it explicitly tracks _less_ superfluous transitions.  
> > 
> > I think it is about triggering on OFF->OFF a warning, as that would
> > only happen if we have:
> > 
> > 	local_irq_save(flags);
> > 	[..]
> > 	local_irq_disable();
> >   
> 
> Ahh, ok. Yes, that is easier to do with these changes. The alternative
> is to add more information to the tracehooks such that we can do the
> same internally, but whatever.
> 
> Yeah, I'm fine with the proposed change, but maybe improve the Changelog
> a little for slow people like me :-)

Great!

Nicholas,

I know this is an old patch (from last November), but want to send it
again with a proper change log and signed off by?

-- Steve