On Thu, May 30, 2024 at 03:05:21PM -0700, Paul E. McKenney wrote: > On Thu, May 30, 2024 at 02:52:48PM -0700, Nathan Chancellor wrote: > > 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 > > Good catch, and thank you for testing this! Does the updated version > shown below do better? Yes, that matches what I tested locally before I replied initially. Thanks for the quick fix! Cheers, Nathan > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 74e3470afacaa9d2f37db4773a5fef887ac4ef56 > 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. > > [ paulmck: Apply Arnd Bergmann and Nathan Chancellor feedback. ] > > 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..a428e06fe94ee 100644 > --- a/arch/arm/include/asm/cmpxchg.h > +++ b/arch/arm/include/asm/cmpxchg.h > @@ -5,6 +5,7 @@ > #include <linux/irqflags.h> > #include <linux/prefetch.h> > #include <asm/barrier.h> > +#include <linux/cmpxchg-emu.h> > > #if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110) > /* > @@ -162,7 +163,11 @@ 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 /* min ARCH >= ARMv6K */ > case 1: > do { > asm volatile("@ __cmpxchg1\n"
