[2/4] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations

Commit Message

Changbin Du Oct. 18, 2018, 4:25 p.m. UTC

From: Changbin Du <[e-mail]>

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 <[e-mail]>
Acked-by: Steven Rostedt (VMware) <[e-mail]>
---
 Makefile          |  6 ++++++
 lib/Kconfig.debug | 25 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

Comments

Robin Murphy Oct. 18, 2018, 4:57 p.m. UTC | #1

On 18/10/18 17:25, Du Changbin wrote:
> From: Changbin Du <[e-mail]>
> 
> 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 <[e-mail]>
> Acked-by: Steven Rostedt (VMware) <[e-mail]>
> ---
>   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
>

Steven Rostedt Oct. 18, 2018, 4:59 p.m. UTC | #2

On Thu, 18 Oct 2018 16:25:46 +0000
Du Changbin <[e-mail]> wrote:

> From: Changbin Du <[e-mail]>
> 
> 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 <[e-mail]>
> Acked-by: Steven Rostedt (VMware) <[e-mail]>

I have acked patch this before, but this particular patch has extra
changes that I have not acked.



> +config ENABLE_WARN_DEPRECATED
> +	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.
> +

What is that?

-- Steve

Changbin Du Oct. 18, 2018, 5:01 p.m. UTC | #3

On Thu, Oct 18, 2018 at 05:57:56PM +0100, Robin Murphy wrote:
> On 18/10/18 17:25, Du Changbin wrote:
> > From: Changbin Du <[e-mail]>
> > 
> > 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 <[e-mail]>
> > Acked-by: Steven Rostedt (VMware) <[e-mail]>
> > ---
> >   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.
> 
opps, this is a rebasing mistake. Let me update it. Thanks.

> 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
> >

Changbin Du Oct. 18, 2018, 5:03 p.m. UTC | #4

On Thu, Oct 18, 2018 at 12:59:48PM -0400, Steven Rostedt wrote:
> On Thu, 18 Oct 2018 16:25:46 +0000
> Du Changbin <[e-mail]> wrote:
> 
> > From: Changbin Du <[e-mail]>
> > 
> > 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 <[e-mail]>
> > Acked-by: Steven Rostedt (VMware) <[e-mail]>
> 
> I have acked patch this before, but this particular patch has extra
> changes that I have not acked.
>
Steven, no extra changes made. I just wronly rebased it on top of mainline.
:)

> 
> 
> > +config ENABLE_WARN_DEPRECATED
> > +	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.
> > +
> 
> What is that?
> 
> -- Steve

Patch

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
+	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