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?
Thanx, Paul
> Thanks for the quick fix!
>
> Cheers,
> Nathan
>
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit 74e3470afacaa9d2f37db4773a5fef887ac4ef56
> > Author: Paul E. McKenney <[email protected]>
> > 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 <[email protected]>
> > Closes:
> > https://lore.kernel.org/all/[email protected]/
> > Reported-by: Naresh Kamboju <[email protected]>
> > Closes:
> > https://lore.kernel.org/all/CA+G9fYuZ+pf6p8AXMZWtdFtX-gbG8HMaBKp=xbxcdza_qel...@mail.gmail.com/
> > Signed-off-by: Paul E. McKenney <[email protected]>
> > Cc: "Russell King (Oracle)" <[email protected]>
> > Cc: Arnd Bergmann <[email protected]>
> > Cc: Andrew Davis <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: Linus Walleij <[email protected]>
> > Cc: Eric DeVolder <[email protected]>
> > Cc: Rob Herring <[email protected]>
> > Cc: <[email protected]>
> >
> > 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"
