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locking/atomic: cmpxchg: support ARCH_ATOMIC

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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 asm-generic/cmpxchg.h or
asm-generic/cmpxhg-local.h, and it's impractical to convert the headers
and all these architectures in one go. To make it possible to convert
them one-by-one, let's make the asm-generic implementation function as
either cmpxchg*() or arch_cmpxchg*() depending on whether ARCH_ATOMIC is
selected. To do this, the generic implementations are prefixed as
generic_cmpxchg_*(), and preprocessor definitions map
cmpxchg_*()/arch_cmpxchg_*() onto these as appropriate.

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@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210525140232.53872-13-mark.rutland@arm.com
This commit is contained in:
Mark Rutland 2021-05-25 15:02:11 +01:00 committed by Peter Zijlstra
parent 6988631bdf
commit 82b993e824
1 changed files with 44 additions and 17 deletions
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61
include/asm-generic/cmpxchg.h
View File

@ -14,16 +14,14 @@
#include <linux/types.h>
#include <linux/irqflags.h>
#ifndef xchg
/*
* This function doesn't exist, so you'll get a linker error if
* something tries to do an invalidly-sized xchg().
*/
extern void __xchg_called_with_bad_pointer(void);
extern void __generic_xchg_called_with_bad_pointer(void);
static inline
unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
unsigned long __generic_xchg(unsigned long x, volatile void *ptr, int size)
{
unsigned long ret, flags;
@ -75,35 +73,64 @@ unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
#endif /* CONFIG_64BIT */
default:
__xchg_called_with_bad_pointer();
__generic_xchg_called_with_bad_pointer();
return x;
}
}
#define xchg(ptr, x) ({ \
((__typeof__(*(ptr))) \
__xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))); \
#define generic_xchg(ptr, x) ({ \
((__typeof__(*(ptr))) \
__generic_xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))); \
})
#endif /* xchg */
/*
* Atomic compare and exchange.
*/
#include <asm-generic/cmpxchg-local.h>
#ifndef cmpxchg_local
#define cmpxchg_local(ptr, o, n) ({ \
((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o),\
(unsigned long)(n), sizeof(*(ptr)))); \
#define generic_cmpxchg_local(ptr, o, n) ({ \
((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o), \
(unsigned long)(n), sizeof(*(ptr)))); \
})
#define generic_cmpxchg64_local(ptr, o, n) \
__generic_cmpxchg64_local((ptr), (o), (n))
#ifdef CONFIG_ARCH_ATOMIC
#ifndef arch_xchg
#define arch_xchg generic_xchg
#endif
#ifndef arch_cmpxchg_local
#define arch_cmpxchg_local generic_cmpxchg_local
#endif
#ifndef arch_cmpxchg64_local
#define arch_cmpxchg64_local generic_cmpxchg64_local
#endif
#define arch_cmpxchg arch_cmpxchg_local
#define arch_cmpxchg64 arch_cmpxchg64_local
#else /* CONFIG_ARCH_ATOMIC */
#ifndef xchg
#define xchg generic_xchg
#endif
#ifndef cmpxchg_local
#define cmpxchg_local generic_cmpxchg_local
#endif
#ifndef cmpxchg64_local
#define cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
#define cmpxchg64_local generic_cmpxchg64_local
#endif
#define cmpxchg(ptr, o, n) cmpxchg_local((ptr), (o), (n))
#define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
#define cmpxchg cmpxchg_local
#define cmpxchg64 cmpxchg64_local
#endif /* CONFIG_ARCH_ATOMIC */
#endif /* __ASM_GENERIC_CMPXCHG_H */