Re: [PATCH 2.6.6] bootmem.c cleanup

Matt Mackall
2004-05-18T19:52:55Z

On Fri, May 14, 2004 at 01:33:53PM -0700, Andrew Morton wrote:
> Michael Buesch <mbuesch@freenet.de> wrote:
> >
> > - if (!test_and_clear_bit(i, bdata->node_bootmem_map))
> > - BUG();
> > + BUG_ON(!test_and_clear_bit(i, bdata->node_bootmem_map));
>
> Please don't put expressions whihc actually change state inside BUG_ON().
> Someone may decide to make BUG_ON() a no-op to save space.

I've done it and it's fine, we just need to evaluate the condition and
let the compiler optimize it away if it has no side effects.

configurable no-op of BUG and WARN

tiny-mpm/include/asm-i386/bug.h | 7 +++++++
tiny-mpm/init/Kconfig | 11 ++++++++++-
2 files changed, 17 insertions(+), 1 deletion(-)

Index: tiny/include/asm-i386/bug.h
===================================================================
--- tiny.orig/include/asm-i386/bug.h 2004-04-19 14:42:45.000000000 -0500
+++ tiny/include/asm-i386/bug.h 2004-04-19 14:46:19.000000000 -0500
@@ -9,6 +9,12 @@
* undefined" opcode for parsing in the trap handler.
*/

+#ifndef CONFIG_BUG
+#define BUG()
+#define WARN_ON(condition) do { if (condition) ; } while(0)
+#define BUG_ON(condition) do { if (condition) ; } while(0)
+#define PAGE_BUG(page)
+#else
#ifdef CONFIG_FULL_BUG
#define BUG() \
__asm__ __volatile__( "ud2\n" \
@@ -40,3 +46,4 @@
} while (0)

#endif
+#endif
Index: tiny/init/Kconfig
===================================================================
--- tiny.orig/init/Kconfig 2004-04-19 14:42:49.000000000 -0500
+++ tiny/init/Kconfig 2004-04-19 14:46:19.000000000 -0500
@@ -274,8 +274,17 @@
very difficult to diagnose system problems, saying N here on
non-embedded systems is strongly discouraged.

+config BUG
+ depends X86
+ default y
+ bool "Enable BUG and WARN code" if EMBEDDED
+ help
+ Disabling this completely removes BUG and WARN checking
+ code. Warning: this may result in data loss if a bug goes
+ undetected.
+
config FULL_BUG
- depends X86
+ depends X86 && BUG
default y
bool "Full BUG reporting code" if EMBEDDED
help

>
> I'm not aware of anyone actually trying that, but it's a good objective.
> -
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--
Matt Mackall : http://www.selenic.com : Linux development and consulting