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s390/cmpxchg: Provide arch_try_cmpxchg()

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Since gcc 14 flag output operands are supported also for s390.

Provide an arch_try_cmpxchg() implementation so that all existing
try_cmpxchg() variants provide slightly better code, if compiled
with gcc 14 or newer.

Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2024-11-06 11:03:07 +01:00
parent c8603d6928
commit 0b6de9aec2
2 changed files with 64 additions and 0 deletions
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12
arch/s390/include/asm/asm.h Normal file
View File

@ -0,0 +1,12 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_S390_ASM_H
#define _ASM_S390_ASM_H
/* GCC versions before 14.2.0 may die with an ICE in some configurations. */
#if defined(__GCC_ASM_FLAG_OUTPUTS__) && !(IS_ENABLED(CONFIG_CC_IS_GCC) && (GCC_VERSION < 140200))
#define __HAVE_ASM_FLAG_OUTPUTS__
#endif
#endif /* _ASM_S390_ASM_H */

52
arch/s390/include/asm/cmpxchg.h
View File

@ -11,6 +11,7 @@
#include <linux/mmdebug.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <asm/asm.h>
void __xchg_called_with_bad_pointer(void);
@ -174,6 +175,57 @@ static __always_inline u64 __arch_cmpxchg(u64 ptr, u64 old, u64 new, int size)
#define arch_cmpxchg_local arch_cmpxchg
#define arch_cmpxchg64_local arch_cmpxchg
#ifdef __HAVE_ASM_FLAG_OUTPUTS__
#define arch_try_cmpxchg(ptr, oldp, new) \
({ \
__typeof__(ptr) __oldp = (__typeof__(ptr))(oldp); \
__typeof__(*(ptr)) __old = *__oldp; \
__typeof__(*(ptr)) __new = (new); \
__typeof__(*(ptr)) __prev; \
int __cc; \
\
switch (sizeof(*(ptr))) { \
case 1: \
case 2: { \
__prev = arch_cmpxchg((ptr), (__old), (__new)); \
__cc = (__prev != __old); \
if (unlikely(__cc)) \
*__oldp = __prev; \
break; \
} \
case 4: { \
asm volatile( \
" cs %[__old],%[__new],%[__ptr]\n" \
: [__old] "+d" (*__oldp), \
[__ptr] "+Q" (*(ptr)), \
"=@cc" (__cc) \
: [__new] "d" (__new) \
: "memory"); \
break; \
} \
case 8: { \
asm volatile( \
" csg %[__old],%[__new],%[__ptr]\n" \
: [__old] "+d" (*__oldp), \
[__ptr] "+QS" (*(ptr)), \
"=@cc" (__cc) \
: [__new] "d" (__new) \
: "memory"); \
break; \
} \
default: \
__cmpxchg_called_with_bad_pointer(); \
} \
likely(__cc == 0); \
})
#define arch_try_cmpxchg64 arch_try_cmpxchg
#define arch_try_cmpxchg_local arch_try_cmpxchg
#define arch_try_cmpxchg64_local arch_try_cmpxchg
#endif /* __HAVE_ASM_FLAG_OUTPUTS__ */
#define system_has_cmpxchg128() 1
static __always_inline u128 arch_cmpxchg128(volatile u128 *ptr, u128 old, u128 new)