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Message-ID: <fb84bb7f-a621-406a-8d1a-51be17caa712@paulmck-laptop>
Date: Fri, 31 May 2024 12:42:26 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, Russell King <linux@...linux.org.uk>,
Naresh Kamboju <naresh.kamboju@...aro.org>,
open list <linux-kernel@...r.kernel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
lkft-triage@...ts.linaro.org,
Linux Regressions <regressions@...ts.linux.dev>,
rcu <rcu@...r.kernel.org>, Dan Carpenter <dan.carpenter@...aro.org>,
Joel Fernandes <joel@...lfernandes.org>, neeraj.upadhyay@...nel.org,
John Ogness <john.ogness@...utronix.de>, broonie@...nel.org
Subject: Re: arm-linux-gnueabihf-ld:
kernel/rcu/update.o:update.c:(.text+0x1cc4): more undefined references to
`__bad_cmpxchg' follow
On Fri, May 31, 2024 at 09:27:22AM -0700, Nathan Chancellor wrote:
> 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@...nel.org>
Thank you! I will apply this on my next rebase.
Thanx, Paul
> > > > ------------------------------------------------------------------------
> > > >
> > > > commit 74e3470afacaa9d2f37db4773a5fef887ac4ef56
> > > > Author: Paul E. McKenney <paulmck@...nel.org>
> > > > 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@...nel.org>
> > > > Closes: https://lore.kernel.org/all/54798f68-48f7-4c65-9cba-47c0bf175143@sirena.org.uk/
> > > > Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> > > > Closes: https://lore.kernel.org/all/CA+G9fYuZ+pf6p8AXMZWtdFtX-gbG8HMaBKp=XbxcdzA_QeLkxQ@mail.gmail.com/
> > > > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > > > Cc: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
> > > > Cc: Arnd Bergmann <arnd@...db.de>
> > > > Cc: Andrew Davis <afd@...com>
> > > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > > Cc: Linus Walleij <linus.walleij@...aro.org>
> > > > Cc: Eric DeVolder <eric.devolder@...cle.com>
> > > > Cc: Rob Herring <robh@...nel.org>
> > > > Cc: <linux-arm-kernel@...ts.infradead.org>
> > > >
> > > > 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"
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