mbox series

[v3,0/2] printk: CONFIG_BASE_SMALL fix for LOG_CPU_MAX_BUF_SHIFT and removal

Message ID 20240204232945.1576403-1-yoann.congal@smile.fr
Headers show
Series printk: CONFIG_BASE_SMALL fix for LOG_CPU_MAX_BUF_SHIFT and removal | expand

Message

Yoann Congal Feb. 4, 2024, 11:29 p.m. UTC 
This series focuses on CONFIG_BASE_SMALL.
The first patch fixes LOG_CPU_MAX_BUF_SHIFT when CONFIG_BASE_SMALL is
used.
The second patch globally replace CONFIG_BASE_SMALL usages by the
equivalent !CONFIG_BASE_FULL.

Patch history:
v2 -> v3: Applied Luis Chamberlain's comments (Thanks!):
* Split the single commit in two : one functional fix, one global
  removal.

v2 patch was named "printk: Remove redundant CONFIG_BASE_SMALL"
https://lore.kernel.org/all/20240127220026.1722399-1-yoann.congal@smile.fr/
* Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
* Reviewed-by: John Ogness <john.ogness@linutronix.de>

v1 -> v2: Applied Masahiro Yamada's comments (Thanks!):
* Changed from "Change CONFIG_BASE_SMALL to type bool" to
  "Remove it and switch usage to !CONFIG_BASE_FULL"
* Fixed "Fixes:" tag and reference to the mailing list thread.
* Added a note about CONFIG_LOG_CPU_MAX_BUF_SHIFT changing.

v1 patch was named "treewide: Change CONFIG_BASE_SMALL to bool type"
https://lore.kernel.org/all/20240126163032.1613731-1-yoann.congal@smile.fr/

Yoann Congal (2):
  printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled
  printk: Remove redundant CONFIG_BASE_SMALL

 arch/x86/include/asm/mpspec.h | 2 +-
 drivers/tty/vt/vc_screen.c    | 2 +-
 include/linux/threads.h       | 6 +++---
 include/linux/udp.h           | 2 +-
 include/linux/xarray.h        | 2 +-
 init/Kconfig                  | 9 ++-------
 kernel/futex/core.c           | 6 +++---
 kernel/user.c                 | 2 +-
 8 files changed, 13 insertions(+), 18 deletions(-)

Comments

Masahiro Yamada Feb. 5, 2024, 3:02 a.m. UTC | #1 
On Mon, Feb 5, 2024 at 8:30 AM Yoann Congal <yoann.congal@smile.fr> 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 BASE_FULL (type bool) which is equivalent
> to 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).
>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> 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")
> ---
>  init/Kconfig | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)



Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
John Ogness Feb. 5, 2024, 8:39 a.m. UTC | #2 
On 2024-02-05, Yoann Congal <yoann.congal@smile.fr> 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 BASE_FULL (type bool) which is equivalent
> to 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).
>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> 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: John Ogness <john.ogness@linutronix.de>