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From: changbin.du@intel.com
To: yamada.masahiro@socionext.com, michal.lkml@markovi.net,
	tglx@linutronix.de, mingo@redhat.com, akpm@linux-foundation.org
Cc: rostedt@goodmis.org, rdunlap@infradead.org, x86@kernel.org,
	lgirdwood@gmail.com, broonie@kernel.org, arnd@arndb.de,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org, Changbin Du <changbin.du@intel.com>
Subject: [PATCH v2 3/5] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations
Date: Wed,  2 May 2018 21:44:58 +0800	[thread overview]
Message-ID: <1525268700-10631-4-git-send-email-changbin.du@intel.com> (raw)
In-Reply-To: <1525268700-10631-1-git-send-email-changbin.du@intel.com>

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>
Cc: Steven Rostedt <rostedt@goodmis.org>

---
v2: Some grammar updates from Steven.
---
 Makefile          |  6 ++++++
 lib/Kconfig.debug | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/Makefile b/Makefile
index 619a85a..eb694f6 100644
--- a/Makefile
+++ b/Makefile
@@ -775,6 +775,12 @@ 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
 ifndef CC_FLAGS_FTRACE
 CC_FLAGS_FTRACE := -pg
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c40c7b7..ab55801 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -198,6 +198,24 @@ 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"
+	default n
+	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
-- 
2.7.4

  parent reply	other threads:[~2018-05-02 13:56 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-02 13:44 [PATCH v2 0/5] kernel hacking: GCC optimization for debug experience (-Og) changbin.du
2018-05-02 13:44 ` [PATCH v2 1/5] x86/mm: surround level4_kernel_pgt with #ifdef CONFIG_X86_5LEVEL...#endif changbin.du
2018-05-02 13:44 ` [PATCH v2 2/5] regulator: add dummy function of_find_regulator_by_node changbin.du
2018-05-02 13:44 ` changbin.du [this message]
2018-05-02 14:07   ` [PATCH v2 3/5] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations Steven Rostedt
2018-05-02 20:27   ` Arnd Bergmann
2018-05-03 13:00     ` Du, Changbin
2018-05-03 14:16       ` Steven Rostedt
2018-05-02 13:44 ` [PATCH v2 4/5] kernel hacking: new config DEBUG_EXPERIENCE to apply GCC -Og optimization changbin.du
2018-05-02 14:17   ` Steven Rostedt
2018-05-02 20:45     ` Andrew Morton
2018-05-03  1:19       ` Steven Rostedt
2018-05-03 13:45         ` Du, Changbin
2018-05-03 14:28           ` Steven Rostedt
2018-05-05 23:57             ` Du, Changbin
2018-05-06  0:27               ` Randy Dunlap
2018-05-02 19:26   ` Randy Dunlap
2018-05-02 13:45 ` [PATCH v2 5/5] asm-generic: fix build error in fix_to_virt with CONFIG_DEBUG_EXPERIENCE changbin.du
2018-05-02 14:19   ` Steven Rostedt
2018-05-03 13:25     ` Du, Changbin
2018-05-03 14:19       ` Steven Rostedt
2018-05-03 16:39         ` weylin
2018-05-02 14:56 ` [PATCH v2 0/5] kernel hacking: GCC optimization for debug experience (-Og) Daniel Thompson
2018-05-03 13:49   ` Du, Changbin

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