Re: [PATCH] asm-generic: atomic64: handle ARCH_ATOMIC builds (was "Re: [PATCH v3 1/2] locking/atomics: Fixup GENERIC_ATOMIC64 conflict") with atomic-arch-fallback.h

From: Guo Ren
Date: Thu Apr 22 2021 - 09:12:38 EST

Hi Mark,

On Thu, Apr 22, 2021 at 6:59 PM Mark Rutland <mark.rutland@xxxxxxx> wrote:
>
> Hi Guo,
>
> On Wed, Apr 21, 2021 at 12:53:45PM +0000, guoren@xxxxxxxxxx wrote:
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > Current GENERIC_ATOMIC64 in atomic-arch-fallback.h is broken. When a 32-bit
> > arch use atomic-arch-fallback.h will cause compile error.
> >
> > In file included from include/linux/atomic.h:81,
> > from include/linux/rcupdate.h:25,
> > from include/linux/rculist.h:11,
> > from include/linux/pid.h:5,
> > from include/linux/sched.h:14,
> > from arch/riscv/kernel/asm-offsets.c:10:
> > include/linux/atomic-arch-fallback.h: In function 'arch_atomic64_inc':
> > >> include/linux/atomic-arch-fallback.h:1447:2: error: implicit declaration of function 'arch_atomic64_add'; did you mean 'arch_atomic_add'? [-Werror=implicit-function-declaration]
> > 1447 | arch_atomic64_add(1, v);
> > | ^~~~~~~~~~~~~~~~~
> > | arch_atomic_add
>
> This is expected; GENERIC_ATOMIC64 doesn't implement arch_atomic64_*(),
> and thus violates the expectations of the fallback code.
>
> To make GENERIC_ATOMIC64 compatible with ARCH_ATOMIC, the
> GENERIC_ATOMIC64 implementation *must* provide arch_atomic64_*()
> functions.
How do you let a "static __always_inline" of
"asm-generic/atomic-instrumented.h" call a real function? See
lib/atomic64.c.

>
> > The atomic-arch-fallback.h & atomic-fallback.h &
> > atomic-instrumented.h are generated by gen-atomic-fallback.sh &
> > gen-atomic-instrumented.sh, so just take care the bash files.
> >
> > Remove the dependency of atomic-*-fallback.h in atomic64.h.
>
> Please don't duplicate the fallbacks; this'll make it harder to move
> other over and eventually remove the non-ARCH_ATOMIC implementations.
>
> Does the patch below make things work for you, or have I missed
> something?
RISC-V combines 32bit & 64bit together just like x86. Current
ARCH_ATOMIC could work perfectly with RV64, but not RV32.

RV32 still could use ARCH_ATOMIC to improve kasan check.

>
> I've given this a basic build test on an arm config using
> GENERIC_ATOMIC64 (but not ARCH_ATOMIC).
>
> Thanks,
> Mark.
> ---->8----
> From 7f0389c8a1f41ecb5b2700f6ba38ff2ba093eb33 Mon Sep 17 00:00:00 2001
> From: Mark Rutland <mark.rutland@xxxxxxx>
> Date: Thu, 22 Apr 2021 11:26:04 +0100
> Subject: [PATCH] asm-generic: atomic64: handle ARCH_ATOMIC builds
>
> We'd like all architectures to convert to ARCH_ATOMIC, as this will
> enable functionality, and once all architectures are converted it will
> be possible to make significant cleanups to the atomic headers.
>
> A number of architectures use GENERIC_ATOMIC64, and it's impractical to
> convert them all in one go. To make it possible to convert them
> one-by-one, let's make the GENERIC_ATOMIC64 implementation function as
> either atomic64_*() or arch_atomic64_*() depending on whether
> ARCH_ATOMIC is selected. To do this, the C implementations are prefixed
> as generic_atomic64_*(), and the asm-generic/atomic64.h header maps
> atomic64_*()/arch_atomic64_*() onto these as appropriate via teh
> preprocessor.
>
> Once all users are moved over to ARCH_ATOMIC the ifdeffery in the header
> can be simplified and/or removed entirely.
>
> For existing users (none of which select ARCH_ATOMIC), there should be
> no functional change as a result of this patch.
>
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> ---
> include/asm-generic/atomic64.h | 74 ++++++++++++++++++++++++++++++++++--------
> lib/atomic64.c | 36 ++++++++++----------
> 2 files changed, 79 insertions(+), 31 deletions(-)
>
> diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
> index 370f01d4450f..45c7ff8c9477 100644
> --- a/include/asm-generic/atomic64.h
> +++ b/include/asm-generic/atomic64.h
> @@ -15,19 +15,17 @@ typedef struct {
>
> #define ATOMIC64_INIT(i) { (i) }
>
> -extern s64 atomic64_read(const atomic64_t *v);
> -extern void atomic64_set(atomic64_t *v, s64 i);
> -
> -#define atomic64_set_release(v, i) atomic64_set((v), (i))
> +extern s64 generic_atomic64_read(const atomic64_t *v);
> +extern void generic_atomic64_set(atomic64_t *v, s64 i);
>
> #define ATOMIC64_OP(op) \
> -extern void atomic64_##op(s64 a, atomic64_t *v);
> +extern void generic_atomic64_##op(s64 a, atomic64_t *v);
>
> #define ATOMIC64_OP_RETURN(op) \
> -extern s64 atomic64_##op##_return(s64 a, atomic64_t *v);
> +extern s64 generic_atomic64_##op##_return(s64 a, atomic64_t *v);
>
> #define ATOMIC64_FETCH_OP(op) \
> -extern s64 atomic64_fetch_##op(s64 a, atomic64_t *v);
> +extern s64 generic_atomic64_fetch_##op(s64 a, atomic64_t *v);
>
> #define ATOMIC64_OPS(op) ATOMIC64_OP(op) ATOMIC64_OP_RETURN(op) ATOMIC64_FETCH_OP(op)
>
> @@ -46,11 +44,61 @@ ATOMIC64_OPS(xor)
> #undef ATOMIC64_OP_RETURN
> #undef ATOMIC64_OP
>
> -extern s64 atomic64_dec_if_positive(atomic64_t *v);
> -#define atomic64_dec_if_positive atomic64_dec_if_positive
> -extern s64 atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n);
> -extern s64 atomic64_xchg(atomic64_t *v, s64 new);
> -extern s64 atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u);
> -#define atomic64_fetch_add_unless atomic64_fetch_add_unless
> +extern s64 generic_atomic64_dec_if_positive(atomic64_t *v);
> +extern s64 generic_atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n);
> +extern s64 generic_atomic64_xchg(atomic64_t *v, s64 new);
> +extern s64 generic_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u);
> +
> +#ifdef ARCH_ATOMIC
> +
> +#define arch_atomic64_read generic_atomic64_read
> +#define arch_atomic64_set generic_atomic64_set
> +#define arch_atomic64_set_release generic_atomic64_set
> +
> +#define arch_atomic64_add generic_atomic64_add
> +#define arch_atomic64_add_return generic_atomic64_add_return
> +#define arch_atomic64_fetch_add generic_atomic64_fetch_add
> +#define arch_atomic64_sub generic_atomic64_sub
> +#define arch_atomic64_sub_return generic_atomic64_sub_return
> +#define arch_atomic64_fetch_sub generic_atomic64_fetch_sub
> +
> +#define arch_atomic64_and generic_atomic64_and
> +#define arch_atomic64_fetch_and generic_atomic64_fetch_and
> +#define arch_atomic64_or generic_atomic64_or
> +#define arch_atomic64_fetch_or generic_atomic64_fetch_or
> +#define arch_atomic64_xor generic_atomic64_xor
> +#define arch_atomic64_fetch_xor generic_atomic64_fetch_xor
> +
> +#define arch_atomic64_dec_if_positive generic_atomic64_dec_if_positive
> +#define arch_atomic64_cmpxchg generic_atomic64_cmpxchg
> +#define arch_atomic64_xchg generic_atomic64_xchg
> +#define arch_atomic64_fetch_add_unless generic_atomic64_fetch_add_unless
> +
> +#else /* ARCH_ATOMIC */
> +
> +#define atomic64_read generic_atomic64_read
> +#define atomic64_set generic_atomic64_set
> +#define atomic64_set_release generic_atomic64_set
> +
> +#define atomic64_add generic_atomic64_add
> +#define atomic64_add_return generic_atomic64_add_return
> +#define atomic64_fetch_add generic_atomic64_fetch_add
> +#define atomic64_sub generic_atomic64_sub
> +#define atomic64_sub_return generic_atomic64_sub_return
> +#define atomic64_fetch_sub generic_atomic64_fetch_sub
> +
> +#define atomic64_and generic_atomic64_and
> +#define atomic64_fetch_and generic_atomic64_fetch_and
> +#define atomic64_or generic_atomic64_or
> +#define atomic64_fetch_or generic_atomic64_fetch_or
> +#define atomic64_xor generic_atomic64_xor
> +#define atomic64_fetch_xor generic_atomic64_fetch_xor
> +
> +#define atomic64_dec_if_positive generic_atomic64_dec_if_positive
> +#define atomic64_cmpxchg generic_atomic64_cmpxchg
> +#define atomic64_xchg generic_atomic64_xchg
> +#define atomic64_fetch_add_unless generic_atomic64_fetch_add_unless
> +
> +#endif /* ARCH_ATOMIC */
>
> #endif /* _ASM_GENERIC_ATOMIC64_H */
> diff --git a/lib/atomic64.c b/lib/atomic64.c
> index e98c85a99787..3df653994177 100644
> --- a/lib/atomic64.c
> +++ b/lib/atomic64.c
> @@ -42,7 +42,7 @@ static inline raw_spinlock_t *lock_addr(const atomic64_t *v)
> return &atomic64_lock[addr & (NR_LOCKS - 1)].lock;
> }
>
> -s64 atomic64_read(const atomic64_t *v)
> +s64 generic_atomic64_read(const atomic64_t *v)
> {
> unsigned long flags;
> raw_spinlock_t *lock = lock_addr(v);
> @@ -53,9 +53,9 @@ s64 atomic64_read(const atomic64_t *v)
> raw_spin_unlock_irqrestore(lock, flags);
> return val;
> }
> -EXPORT_SYMBOL(atomic64_read);
> +EXPORT_SYMBOL(generic_atomic64_read);
>
> -void atomic64_set(atomic64_t *v, s64 i)
> +void generic_atomic64_set(atomic64_t *v, s64 i)
> {
> unsigned long flags;
> raw_spinlock_t *lock = lock_addr(v);
> @@ -64,10 +64,10 @@ void atomic64_set(atomic64_t *v, s64 i)
> v->counter = i;
> raw_spin_unlock_irqrestore(lock, flags);
> }
> -EXPORT_SYMBOL(atomic64_set);
> +EXPORT_SYMBOL(generic_atomic64_set);
>
> #define ATOMIC64_OP(op, c_op) \
> -void atomic64_##op(s64 a, atomic64_t *v) \
> +void generic_atomic64_##op(s64 a, atomic64_t *v) \
> { \
> unsigned long flags; \
> raw_spinlock_t *lock = lock_addr(v); \
> @@ -76,10 +76,10 @@ void atomic64_##op(s64 a, atomic64_t *v) \
> v->counter c_op a; \
> raw_spin_unlock_irqrestore(lock, flags); \
> } \
> -EXPORT_SYMBOL(atomic64_##op);
> +EXPORT_SYMBOL(generic_atomic64_##op);
>
> #define ATOMIC64_OP_RETURN(op, c_op) \
> -s64 atomic64_##op##_return(s64 a, atomic64_t *v) \
> +s64 generic_atomic64_##op##_return(s64 a, atomic64_t *v) \
> { \
> unsigned long flags; \
> raw_spinlock_t *lock = lock_addr(v); \
> @@ -90,10 +90,10 @@ s64 atomic64_##op##_return(s64 a, atomic64_t *v) \
> raw_spin_unlock_irqrestore(lock, flags); \
> return val; \
> } \
> -EXPORT_SYMBOL(atomic64_##op##_return);
> +EXPORT_SYMBOL(generic_atomic64_##op##_return);
>
> #define ATOMIC64_FETCH_OP(op, c_op) \
> -s64 atomic64_fetch_##op(s64 a, atomic64_t *v) \
> +s64 generic_atomic64_fetch_##op(s64 a, atomic64_t *v) \
> { \
> unsigned long flags; \
> raw_spinlock_t *lock = lock_addr(v); \
> @@ -105,7 +105,7 @@ s64 atomic64_fetch_##op(s64 a, atomic64_t *v) \
> raw_spin_unlock_irqrestore(lock, flags); \
> return val; \
> } \
> -EXPORT_SYMBOL(atomic64_fetch_##op);
> +EXPORT_SYMBOL(generic_atomic64_fetch_##op);
>
> #define ATOMIC64_OPS(op, c_op) \
> ATOMIC64_OP(op, c_op) \
> @@ -130,7 +130,7 @@ ATOMIC64_OPS(xor, ^=)
> #undef ATOMIC64_OP_RETURN
> #undef ATOMIC64_OP
>
> -s64 atomic64_dec_if_positive(atomic64_t *v)
> +s64 generic_atomic64_dec_if_positive(atomic64_t *v)
> {
> unsigned long flags;
> raw_spinlock_t *lock = lock_addr(v);
> @@ -143,9 +143,9 @@ s64 atomic64_dec_if_positive(atomic64_t *v)
> raw_spin_unlock_irqrestore(lock, flags);
> return val;
> }
> -EXPORT_SYMBOL(atomic64_dec_if_positive);
> +EXPORT_SYMBOL(generic_atomic64_dec_if_positive);
>
> -s64 atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n)
> +s64 generic_atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n)
> {
> unsigned long flags;
> raw_spinlock_t *lock = lock_addr(v);
> @@ -158,9 +158,9 @@ s64 atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n)
> raw_spin_unlock_irqrestore(lock, flags);
> return val;
> }
> -EXPORT_SYMBOL(atomic64_cmpxchg);
> +EXPORT_SYMBOL(generic_atomic64_cmpxchg);
>
> -s64 atomic64_xchg(atomic64_t *v, s64 new)
> +s64 generic_atomic64_xchg(atomic64_t *v, s64 new)
> {
> unsigned long flags;
> raw_spinlock_t *lock = lock_addr(v);
> @@ -172,9 +172,9 @@ s64 atomic64_xchg(atomic64_t *v, s64 new)
> raw_spin_unlock_irqrestore(lock, flags);
> return val;
> }
> -EXPORT_SYMBOL(atomic64_xchg);
> +EXPORT_SYMBOL(generic_atomic64_xchg);
>
> -s64 atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
> +s64 generic_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
> {
> unsigned long flags;
> raw_spinlock_t *lock = lock_addr(v);
> @@ -188,4 +188,4 @@ s64 atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
>
> return val;
> }
> -EXPORT_SYMBOL(atomic64_fetch_add_unless);
> +EXPORT_SYMBOL(generic_atomic64_fetch_add_unless);
> --
> 2.11.0
>


--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/