printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled
LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL:
config LOG_CPU_MAX_BUF_SHIFT
default 12 if !BASE_SMALL
default 0 if BASE_SMALL
But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always
evaluated to true whatever is the value of BASE_SMALL.
This patch fixes this by using the correct conditional operator for int
type : BASE_SMALL != 0.
Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to
CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will
not be a big impact due to this code in kernel/printk/printk.c:
/* by default this will only continue through for large > 64 CPUs */
if (cpu_extra <= __LOG_BUF_LEN / 2)
return;
Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite
rare.
John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote:
> For printk this will mean that BASE_SMALL systems were probably
> previously allocating/using the dynamic ringbuffer and now they will
> just continue to use the static ringbuffer. Which is fine and saves
> memory (as it should).
Petr Mladek <pmladek@suse.com> (printk maintainer) wrote:
> More precisely, it allocated the buffer dynamically when the sum
> of per-CPU-extra space exceeded half of the default static ring
> buffer. This happened for systems with more than 64 CPUs with
> the default config values.
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/
Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Link: https://lore.kernel.org/r/20240505080343.1471198-2-yoann.congal@smile.fr
Signed-off-by: Petr Mladek <pmladek@suse.com>
diff --git a/init/Kconfig b/init/Kconfig
index f3ea5de..ff5b607 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -743,8 +743,8 @@
int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
depends on SMP
range 0 21
- default 12 if !BASE_SMALL
- default 0 if BASE_SMALL
+ default 0 if BASE_SMALL != 0
+ default 12
depends on PRINTK
help
This option allows to increase the default ring buffer size
