6.9-stable review patch. If anyone has any objections, please let me know.
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From: Yoann Congal yoann.congal@smile.fr
[ Upstream commit 320bf43190514be5c00e11f47ec2160dd3993844 ]
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=2XUAHascps76YQac6rdnQGhc8no... 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 Signed-off-by: Sasha Levin sashal@kernel.org --- init/Kconfig | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig index 664bedb9a71fb..459f44ef7cc94 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -743,8 +743,8 @@ config LOG_CPU_MAX_BUF_SHIFT 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