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Subject: Re: [PATCH] irqtrace-option-off-compile-fix
From: Tim Chen <tim.c.chen@linux.intel.com>
Reply-To: tim.c.chen@linux.intel.com
To: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@infradead.org>, linux-kernel@vger.kernel.org,
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Organization: Intel
Date: Tue, 11 Jul 2006 12:48:58 -0700
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On Tue, 2006-07-11 at 21:45 +0200, Ingo Molnar wrote:
> * Tim Chen <tim.c.chen@linux.intel.com> wrote:
> 
> > > The one you want is CONFIG_TRACE_IRQFLAGS .. which is the one that 
> > > actually turns the tracing on
> > 
> > I could not turn off CONFIG_TRACE_IRQFLAGS_SUPPORT in .config 
> > directly. The command "scripts/kconfig/conf -s arch/x86_64/Kconfig" in 
> > Makefile overwrites changes made to CONFIG_TRACE_IRQFLAGS_SUPPORT in 
> > .config file.  So this is always turned on in .config if the option 
> > TRACE_IRQFLAGS_SUPPORT is set in arch/x86_64/Kconfig.debug.  I may be 
> > missing something.  Any suggestions?
> 
> correct, that flag is always set - it signals towards the core kernel 
> that the architecture in question (x86_64) that it has trace-irqflags 
> support. NOTE: this does not mean that irqflags tracing is turned on - 
> that is another option: CONFIG_TRACE_IRQFLAGS.
> 
> unsetting the support flag makes no sense and will likely break the 
> build. There is no overhead from irqflags tracing if it's turned off. 
> (even if the CONFIG_TRACE_IRQFLAGS_SUPPORT option is set)
> 
> does this explain things? We could rename the boolean value to 
> CONFIG_TRACE_IRQFLAGS_SUPPORT_AVAILABLE perhaps, to avoid future 
> confusion.
> 
> 	Ingo

Thanks for clarifying.