On Thu, May 30, 2024 at 10:24:05AM -0700, Paul E. McKenney wrote:
> And for an untested first attempt at a fix.
>
> What did I mess up this time? ;-)
An include for cmpxchg-emu.h ;)
In file included from arch/arm/include/asm/atomic.h:16,
from include/linux/atomic.h:7,
from include/asm-generic/bitops/lock.h:5,
from arch/arm/include/asm/bitops.h:245,
from include/linux/bitops.h:63,
from include/linux/log2.h:12,
from kernel/bounds.c:13:
arch/arm/include/asm/cmpxchg.h: In function '__cmpxchg':
arch/arm/include/asm/cmpxchg.h:167:26: error: implicit declaration of function 'cmpxchg_emu_u8' [-Werror=implicit-function-declaration]
167 | oldval = cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
| ^~~~~~~~~~~~~~
cc1: some warnings being treated as errors
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 6e43483dd111cf1be58b02a45d0ca729ca2634ba
> Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Date: Thu May 30 10:11:31 2024 -0700
>
> ARM: Emulate one-byte cmpxchg
>
> Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on ARM systems
> with ARCH < ARMv6K.
>
> Reported-by: Mark Brown <broonie@xxxxxxxxxx>
> Closes: https://lore.kernel.org/all/54798f68-48f7-4c65-9cba-47c0bf175143@xxxxxxxxxxxxx/
> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Closes: https://lore.kernel.org/all/CA+G9fYuZ+pf6p8AXMZWtdFtX-gbG8HMaBKp=XbxcdzA_QeLkxQ@xxxxxxxxxxxxxx/
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: "Russell King (Oracle)" <rmk+kernel@xxxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Andrew Davis <afd@xxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Eric DeVolder <eric.devolder@xxxxxxxxxx>
> Cc: Rob Herring <robh@xxxxxxxxxx>
> Cc: <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index ee5115252aac4..a867a7d967aa5 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -34,6 +34,7 @@ config ARM
> select ARCH_MIGHT_HAVE_PC_PARPORT
> select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
> select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
> + select ARCH_NEED_CMPXCHG_1_EMU if CPU_V6
> select ARCH_SUPPORTS_ATOMIC_RMW
> select ARCH_SUPPORTS_CFI_CLANG
> select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE
> diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
> index 44667bdb4707a..fd9b99f4dca46 100644
> --- a/arch/arm/include/asm/cmpxchg.h
> +++ b/arch/arm/include/asm/cmpxchg.h
> @@ -162,7 +162,11 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
> prefetchw((const void *)ptr);
>
> switch (size) {
> -#ifndef CONFIG_CPU_V6 /* min ARCH >= ARMv6K */
> +#ifdef CONFIG_CPU_V6 /* min ARCH >= ARMv6K */
> + case 1:
> + oldval = cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
> + break;
> +#else
> case 1:
> do {
> asm volatile("@ __cmpxchg1\n"
>
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