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SubjectRe: [PATCH 2/4] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations
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On 18/10/18 17:25, Du Changbin wrote:
> From: Changbin Du <changbin.du@intel.com>
>
> This patch add a new kernel hacking option NO_AUTO_INLINE. Selecting
> this option will prevent the compiler from optimizing the kernel by
> auto-inlining functions not marked with the inline keyword.
>
> With this option, only functions explicitly marked with "inline" will
> be inlined. This will allow the function tracer to trace more functions
> because it only traces functions that the compiler has not inlined.
>
> Signed-off-by: Changbin Du <changbin.du@intel.com>
> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> Makefile | 6 ++++++
> lib/Kconfig.debug | 25 +++++++++++++++++++++++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index e8b599b4dcde..757d6507cb5c 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -749,6 +749,12 @@ KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \
> $(call cc-option,-fno-var-tracking)
> endif
>
> +ifdef CONFIG_NO_AUTO_INLINE
> +KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions) \
> + $(call cc-option, -fno-inline-small-functions) \
> + $(call cc-option, -fno-inline-functions-called-once)
> +endif
> +
> ifdef CONFIG_FUNCTION_TRACER
> ifdef CONFIG_FTRACE_MCOUNT_RECORD
> # gcc 5 supports generating the mcount tables directly
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 4966c4fbe7f7..0f9b4fa78b1c 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -211,6 +211,31 @@ config GDB_SCRIPTS
> instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
> for further details.
>
> +config NO_AUTO_INLINE
> + bool "Disable compiler auto-inline optimizations"
> + help
> + This will prevent the compiler from optimizing the kernel by
> + auto-inlining functions not marked with the inline keyword.
> + With this option, only functions explicitly marked with
> + "inline" will be inlined. This will allow the function tracer
> + to trace more functions because it only traces functions that
> + the compiler has not inlined.
> +
> + Enabling this function can help debugging a kernel if using
> + the function tracer. But it can also change how the kernel
> + works, because inlining functions may change the timing,
> + which could make it difficult while debugging race conditions.
> +
> + If unsure, select N.
> +
> +config ENABLE_WARN_DEPRECATED

This part doesn't look like it belongs in this patch, and judging by the
commit message in 771c035372a0 wouldn't be welcome back anyway.

Robin.

> + bool "Enable __deprecated logic"
> + default y
> + help
> + Enable the __deprecated logic in the kernel build.
> + Disable this to suppress the "warning: 'foo' is deprecated
> + (declared at kernel/power/somefile.c:1234)" messages.
> +
> config ENABLE_MUST_CHECK
> bool "Enable __must_check logic"
> default y
>

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