On Thu, Feb 8, 2024 at 2:10 AM Yoann Congal <yoann.congal@xxxxxxxx> wrote: > > 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@xxxxxxxxxxxxx> (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@xxxxxxxx> (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. > > Signed-off-by: Yoann Congal <yoann.congal@xxxxxxxx> > Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@xxxxxxxxxxxxxx/ > Reported-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> > Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@xxxxxxxxxx/ > Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable") > All the Reviewed-by tags are dropped every time, annoyingly. This is equivalent to v4, which had these tags: Reviewed-by: Petr Mladek <pmladek@xxxxxxxx> Reviewed-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > --- > v3->v4: > * Fix BASE_SMALL usage instead of switching to BASE_FULL because > BASE_FULL will be removed in the next patches of this series. > --- > init/Kconfig | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/init/Kconfig b/init/Kconfig > index deda3d14135bb..d50ebd2a2ce42 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -734,8 +734,8 @@ 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 > -- > 2.39.2 > > -- Best Regards Masahiro Yamada
