Re: [PATCH] irqtrace-option-off-compile-fix

From: Ingo Molnar
Date: Tue Jul 11 2006 - 15:48:46 EST



* Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> 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
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