Messages in this thread | | | From | Masahiro Yamada <> | Date | Tue, 3 Aug 2021 14:14:53 +0900 | Subject | Re: [PATCH 3/3] trace: remove redundant dependency from IRQSOFF_TRACER |
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On Mon, Aug 2, 2021 at 10:29 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Sat, 31 Jul 2021 14:22:33 +0900 > Masahiro Yamada <masahiroy@kernel.org> wrote: > > > IRQSOFF_TRACE is already guarded by a stronger condition, > > TRACING_SUPPORT. > > > > 'depends on TRACE_IRQFLAGS_SUPPORT' is redundant. > > I'm fine with the other two patches, but this one concerns me. I'm not > sure TRACING_SUPPORT really needs to depend on TRACE_IRQFLAGS_SUPPORT. > When tracing was first introduced, the main use case was the irqsoff > tracer. Today, with function graph tracing and events being introduced, > it's one of the minor use cases of tracing support. > > I believe the only thing that requires the TRACE_IRQFLAGS_SUPPORT is > the irqsoff tracer (and friends), so if anything, we should remove that > dependency from TRACING_SUPPORT, not here.
OK. The first two are more trivial, so please pick up 1/3 and 2/3, then drop this one.
BTW, I personally prefer HAVE_* to *_SUPPORT.
Maybe renaming as follows makes the code more consistent.
STACKTRACE_SUPPORT -> HAVE_STACKTRACE TRACE_IRQFLAGS_SUPPORT -> HAVE_TRACE_IRQFLAGS
Documentation/kbuild/kconfig-language.rst says HAVE_* style is the recommended way.
It is a common idiom to implement a feature/functionality that are relevant for some architectures but not all. The recommended way to do so is to use a config variable named HAVE_* that is defined in a common Kconfig file and selected by the relevant architectures. An example is the generic IOMAP functionality.
We would in lib/Kconfig see::
# Generic IOMAP is used to ... config HAVE_GENERIC_IOMAP
config GENERIC_IOMAP depends on HAVE_GENERIC_IOMAP && FOO
> -- Steve > > > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > > --- > > > > kernel/trace/Kconfig | 1 - > > 1 file changed, 1 deletion(-) > > > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > > index 9d3f918b5867..b39e67db644e 100644 > > --- a/kernel/trace/Kconfig > > +++ b/kernel/trace/Kconfig > > @@ -265,7 +265,6 @@ config TRACE_PREEMPT_TOGGLE > > config IRQSOFF_TRACER > > bool "Interrupts-off Latency Tracer" > > default n > > - depends on TRACE_IRQFLAGS_SUPPORT > > select TRACE_IRQFLAGS > > select GENERIC_TRACER > > select TRACER_MAX_TRACE >
-- Best Regards Masahiro Yamada
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