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Message-ID: <CAK7LNATBvhcyQXt58j74Q++Y74ZgjdC3r3rtnAuU0YMt_K_A7g@mail.gmail.com>
Date: Sat, 27 Jan 2024 04:28:44 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Yoann Congal <yoann.congal@...le.fr>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kbuild@...r.kernel.org,
Geert Uytterhoeven <geert@...ux-m68k.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>, Matthew Wilcox <willy@...radead.org>,
Peter Zijlstra <peterz@...radead.org>, Darren Hart <dvhart@...radead.org>,
Davidlohr Bueso <dave@...olabs.net>, André Almeida <andrealmeid@...lia.com>,
"Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: Re: [PATCH] treewide: Change CONFIG_BASE_SMALL to bool type
(+CC: Luis R. Rodriguez, author of 23b2899f7f194)
On Sat, Jan 27, 2024 at 1:30 AM Yoann Congal <yoann.congal@...le.fr> wrote:
>
> CONFIG_BASE_SMALL is currently a type int but is only used as a boolean:
> CONFIG_BASE_SMALL == 0 vs CONFIG_BASE_SMALL != 0.
>
> So change it to the more logical bool type.
>
> Furthermore, recent kconfig changes (see Fixes: tags) revealed that using
Seeing the Fixes tage does not reveal this issue.
The discussion in Closes: thread explains the issue.
> config SOMETHING
> default "some value" if X
> does not work as expected if X is not of type bool.
>
> CONFIG_BASE_SMALL is used that way in init/Kconfig:
> config LOG_CPU_MAX_BUF_SHIFT
> default 12 if !BASE_SMALL
> default 0 if BASE_SMALL
Or, an even cleaner way is to remove BASE_SMALL because it is
the same as !BASE_FULL.
config LOG_CPU_MAX_BUF_SHIFT
default 12 if BASE_FULL
default 0
You also need to invert the logic in C as well.
Perhaps, it might be worth mentioning this changes
CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to
CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for some defconfigs,
but that will not be a big impact due to this code:
/* by default this will only continue through for large > 64 CPUs */
if (cpu_extra <= __LOG_BUF_LEN / 2)
return;
>
> Signed-off-by: Yoann Congal <yoann.congal@...le.fr>
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
> Fixes: 6262afa10ef7 ("kconfig: default to zero if int/hex symbol lacks default property")
This tag is not relevant.
> Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")
This is correct.
> ---
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Borislav Petkov <bp@...en8.de>
> CC: Dave Hansen <dave.hansen@...ux.intel.com>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CC: Jiri Slaby <jirislaby@...nel.org>
> CC: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> CC: Matthew Wilcox <willy@...radead.org>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: Darren Hart <dvhart@...radead.org>
> CC: Davidlohr Bueso <dave@...olabs.net>
> CC: "André Almeida" <andrealmeid@...lia.com>
> CC: Masahiro Yamada <masahiroy@...nel.org>
> CC: x86@...nel.org
> CC: linux-kernel@...r.kernel.org
> CC: linux-serial@...r.kernel.org
> CC: linux-fsdevel@...r.kernel.org
> CC: linux-kbuild@...r.kernel.org
> ---
> arch/x86/include/asm/mpspec.h | 2 +-
> drivers/tty/vt/vc_screen.c | 2 +-
> include/linux/threads.h | 4 ++--
> include/linux/udp.h | 2 +-
> include/linux/xarray.h | 2 +-
> init/Kconfig | 6 +++---
> kernel/futex/core.c | 2 +-
> kernel/user.c | 2 +-
> 8 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
> index 4b0f98a8d338d..ebe4b6121b698 100644
> --- a/arch/x86/include/asm/mpspec.h
> +++ b/arch/x86/include/asm/mpspec.h
> @@ -15,7 +15,7 @@ extern int pic_mode;
> * Summit or generic (i.e. installer) kernels need lots of bus entries.
> * Maximum 256 PCI busses, plus 1 ISA bus in each of 4 cabinets.
> */
> -#if CONFIG_BASE_SMALL == 0
> +#ifndef CONFIG_BASE_SMALL
> # define MAX_MP_BUSSES 260
> #else
> # define MAX_MP_BUSSES 32
> diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
> index 67e2cb7c96eec..da33c6c4691c0 100644
> --- a/drivers/tty/vt/vc_screen.c
> +++ b/drivers/tty/vt/vc_screen.c
> @@ -51,7 +51,7 @@
> #include <asm/unaligned.h>
>
> #define HEADER_SIZE 4u
> -#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
> +#define CON_BUF_SIZE (IS_ENABLED(CONFIG_BASE_SMALL) ? 256 : PAGE_SIZE)
>
> /*
> * Our minor space:
> diff --git a/include/linux/threads.h b/include/linux/threads.h
> index c34173e6c5f18..1674a471b0b4c 100644
> --- a/include/linux/threads.h
> +++ b/include/linux/threads.h
> @@ -25,13 +25,13 @@
> /*
> * This controls the default maximum pid allocated to a process
> */
> -#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000)
> +#define PID_MAX_DEFAULT (IS_ENABLED(CONFIG_BASE_SMALL) ? 0x1000 : 0x8000)
>
> /*
> * A maximum of 4 million PIDs should be enough for a while.
> * [NOTE: PID/TIDs are limited to 2^30 ~= 1 billion, see FUTEX_TID_MASK.]
> */
> -#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
> +#define PID_MAX_LIMIT (IS_ENABLED(CONFIG_BASE_SMALL) ? PAGE_SIZE * 8 : \
> (sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))
>
> /*
> diff --git a/include/linux/udp.h b/include/linux/udp.h
> index d04188714dca1..b456417fb4515 100644
> --- a/include/linux/udp.h
> +++ b/include/linux/udp.h
> @@ -24,7 +24,7 @@ static inline struct udphdr *udp_hdr(const struct sk_buff *skb)
> }
>
> #define UDP_HTABLE_SIZE_MIN_PERNET 128
> -#define UDP_HTABLE_SIZE_MIN (CONFIG_BASE_SMALL ? 128 : 256)
> +#define UDP_HTABLE_SIZE_MIN (IS_ENABLED(CONFIG_BASE_SMALL) ? 128 : 256)
> #define UDP_HTABLE_SIZE_MAX 65536
>
> static inline u32 udp_hashfn(const struct net *net, u32 num, u32 mask)
> diff --git a/include/linux/xarray.h b/include/linux/xarray.h
> index cb571dfcf4b16..3f81ee5f9fb9c 100644
> --- a/include/linux/xarray.h
> +++ b/include/linux/xarray.h
> @@ -1141,7 +1141,7 @@ static inline void xa_release(struct xarray *xa, unsigned long index)
> * doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
> */
> #ifndef XA_CHUNK_SHIFT
> -#define XA_CHUNK_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
> +#define XA_CHUNK_SHIFT (IS_ENABLED(CONFIG_BASE_SMALL) ? 4 : 6)
> #endif
> #define XA_CHUNK_SIZE (1UL << XA_CHUNK_SHIFT)
> #define XA_CHUNK_MASK (XA_CHUNK_SIZE - 1)
> diff --git a/init/Kconfig b/init/Kconfig
> index 8d4e836e1b6b1..766a7ac8c5ea4 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1941,9 +1941,9 @@ config RT_MUTEXES
> default y if PREEMPT_RT
>
> config BASE_SMALL
> - int
> - default 0 if BASE_FULL
> - default 1 if !BASE_FULL
> + bool
> + default n if BASE_FULL
> + default y if !BASE_FULL
>
> config MODULE_SIG_FORMAT
> def_bool n
> diff --git a/kernel/futex/core.c b/kernel/futex/core.c
> index e0e853412c158..5f7aa4fc2f9ee 100644
> --- a/kernel/futex/core.c
> +++ b/kernel/futex/core.c
> @@ -1141,7 +1141,7 @@ static int __init futex_init(void)
> unsigned int futex_shift;
> unsigned long i;
>
> -#if CONFIG_BASE_SMALL
> +#ifdef CONFIG_BASE_SMALL
> futex_hashsize = 16;
> #else
> futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus());
> diff --git a/kernel/user.c b/kernel/user.c
> index 03cedc366dc9e..aa1162deafe49 100644
> --- a/kernel/user.c
> +++ b/kernel/user.c
> @@ -88,7 +88,7 @@ EXPORT_SYMBOL_GPL(init_user_ns);
> * when changing user ID's (ie setuid() and friends).
> */
>
> -#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
> +#define UIDHASH_BITS (IS_ENABLED(CONFIG_BASE_SMALL) ? 3 : 7)
> #define UIDHASH_SZ (1 << UIDHASH_BITS)
> #define UIDHASH_MASK (UIDHASH_SZ - 1)
> #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
> --
> 2.39.2
>
--
Best Regards
Masahiro Yamada
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