On Thu, May 30, 2024 at 05:35:44PM -0700, Paul E. McKenney wrote: > On Thu, May 30, 2024 at 04:30:53PM -0700, Nathan Chancellor wrote: > > 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. > > Very good! May I please add your Tested-by? Sure thing. Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > > ------------------------------------------------------------------------ > > > > > > 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"
