On 27.04.2009 19:48, Patrick Georgi wrote:
> Hi,
>
> the attached patch make printk_* behaviour more consistent. Without it, side
> effects in the arguments (eg. a pci config read, or variable increment)
> "vanish" with the message, and the behaviour changes.
>
Ouch. Great find!
> Example:
> printk_info("foo %d\n", i++);
>
> Without this patch, this becomes (for suitable loglevels)
> do {} while (0)
>
> With this patch, this will be:
> do_printk(EMERG, "", i++);
>
> Some of these effects might be unwanted, but at least they are consistent
> now.
> For example, via c7 CAR failed for loglevel > 7 for various reasons (patch
> upcoming). While it fails all the time now (this patch is no "magic fix"),
> upcoming development is less likely to produce such "hidden surprises".
>
> To reduce the memory footprint slightly, the formatted strings are discarded.
> A simpler patch would be to just kill the whole "#if #undef #define #endif"-
> section, but then a lot of strings that never surface would be compiled in
> (and I doubt the compiler is clever enough to figure that out)
>
> Signed-off-by: Patrick Georgi <[email protected]>
>
Let me propose an alternative which does not have an empty printk call,
yet keeps the side effects of all parameters.
Signed-off-by: Carl-Daniel Hailfinger <[email protected]>
Index: LinuxBIOSv2-printk_level_side_effects/src/arch/i386/lib/console_printk.c
===================================================================
--- LinuxBIOSv2-printk_level_side_effects/src/arch/i386/lib/console_printk.c
(Revision 4217)
+++ LinuxBIOSv2-printk_level_side_effects/src/arch/i386/lib/console_printk.c
(Arbeitskopie)
@@ -13,39 +13,39 @@
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_EMERG
#undef printk_emerg
-#define printk_emerg(fmt, arg...) do {} while(0)
+#define printk_emerg(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_ALERT
#undef printk_alert
-#define printk_alert(fmt, arg...) do {} while(0)
+#define printk_alert(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_CRIT
#undef printk_crit
-#define printk_crit(fmt, arg...) do {} while(0)
+#define printk_crit(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_ERR
#undef printk_err
-#define printk_err(fmt, arg...) do {} while(0)
+#define printk_err(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_WARNING
#undef printk_warning
-#define printk_warning(fmt, arg...) do {} while(0)
+#define printk_warning(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_NOTICE
#undef printk_notice
-#define printk_notice(fmt, arg...) do {} while(0)
+#define printk_notice(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_INFO
#undef printk_info
-#define printk_info(fmt, arg...) do {} while(0)
+#define printk_info(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_DEBUG
#undef printk_debug
-#define printk_debug(fmt, arg...) do {} while(0)
+#define printk_debug(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_SPEW
#undef printk_spew
-#define printk_spew(fmt, arg...) do {} while(0)
+#define printk_spew(fmt, arg...) do { arg; } while(0)
#endif
#define print_emerg(STR) printk_emerg ("%s", (STR))
--
http://www.hailfinger.org/
Index: LinuxBIOSv2-printk_level_side_effects/src/arch/i386/lib/console_printk.c
===================================================================
--- LinuxBIOSv2-printk_level_side_effects/src/arch/i386/lib/console_printk.c (Revision 4217)
+++ LinuxBIOSv2-printk_level_side_effects/src/arch/i386/lib/console_printk.c (Arbeitskopie)
@@ -13,39 +13,39 @@
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_EMERG
#undef printk_emerg
-#define printk_emerg(fmt, arg...) do {} while(0)
+#define printk_emerg(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_ALERT
#undef printk_alert
-#define printk_alert(fmt, arg...) do {} while(0)
+#define printk_alert(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_CRIT
#undef printk_crit
-#define printk_crit(fmt, arg...) do {} while(0)
+#define printk_crit(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_ERR
#undef printk_err
-#define printk_err(fmt, arg...) do {} while(0)
+#define printk_err(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_WARNING
#undef printk_warning
-#define printk_warning(fmt, arg...) do {} while(0)
+#define printk_warning(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_NOTICE
#undef printk_notice
-#define printk_notice(fmt, arg...) do {} while(0)
+#define printk_notice(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_INFO
#undef printk_info
-#define printk_info(fmt, arg...) do {} while(0)
+#define printk_info(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_DEBUG
#undef printk_debug
-#define printk_debug(fmt, arg...) do {} while(0)
+#define printk_debug(fmt, arg...) do { arg; } while(0)
#endif
#if MAXIMUM_CONSOLE_LOGLEVEL <= BIOS_SPEW
#undef printk_spew
-#define printk_spew(fmt, arg...) do {} while(0)
+#define printk_spew(fmt, arg...) do { arg; } while(0)
#endif
#define print_emerg(STR) printk_emerg ("%s", (STR))
--
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