linux-kernel - Re: [PATCH v2] tracing: Don't account for cpu idle time with irqsoff tracers

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Message-ID: <1401237734.23277.1.camel@pippen.local.home>
Date:	Tue, 27 May 2014 20:42:14 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Corey Minyard <cminyard@...sta.com>,
	Stanislav Meduna <stano@...una.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] tracing: Don't account for cpu idle time with
 irqsoff tracers

On Tue, 2014-05-27 at 17:11 -0700, Stephen Boyd wrote:

> cpuidle_enter_state() calls ktime_get() which on lockdep enabled builds
> calls seqcount_lockdep_reader_access() which calls local_irq_save() that

seqcount_lockdep_reader_access()?? Ug, I wonder if that should call
raw_local_irq_save/restore() as it's a lockdep helper to begin with. If
it's wrong then it's the lockdep infrastructure that broke, not the core
kernel.

Peter?

-- Steve


> then turns on the tracer again. Perhaps the problem is that irqsoff
> tracer is triggered even when we aren't transitioning between irqs on
> and irqs off? What about this patch? I assume there is a reason that
> this is wrong, but I don't know what it is.
> 


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