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

[Ingo Molnar <mingo@elte.hu>]

* 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