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s390/spinlock: Use flag output constraint for arch_cmpxchg_niai8()

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Add a new variant of arch_cmpxchg_niai8() which makes use of the flag
output constraint, which allows the compiler to generate slightly better
code. Also rename arch_cmpxchg_niai8() to arch_try_cmpxchg_niai8() which
reflects the purpose of the function and makes it consistent with other
"try" variants.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2024-11-26 14:28:27 +01:00
parent 84ac96587b
commit 889221c4d7
1 changed files with 22 additions and 2 deletions
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24
arch/s390/lib/spinlock.c
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@ -15,6 +15,7 @@
#include <linux/percpu.h>
#include <linux/io.h>
#include <asm/alternative.h>
#include <asm/asm.h>
int spin_retry = -1;
@ -81,7 +82,24 @@ static inline int arch_load_niai4(int *lock)
return owner;
}
static inline int arch_cmpxchg_niai8(int *lock, int old, int new)
#ifdef __HAVE_ASM_FLAG_OUTPUTS__
static inline int arch_try_cmpxchg_niai8(int *lock, int old, int new)
{
int cc;
asm_inline volatile(
ALTERNATIVE("nop", ".insn rre,0xb2fa0000,8,0", ALT_FACILITY(49)) /* NIAI 8 */
" cs %[old],%[new],%[lock]\n"
: [old] "+d" (old), [lock] "+Q" (*lock), "=@cc" (cc)
: [new] "d" (new)
: "memory");
return cc == 0;
}
#else /* __HAVE_ASM_FLAG_OUTPUTS__ */
static inline int arch_try_cmpxchg_niai8(int *lock, int old, int new)
{
int expected = old;
@ -94,6 +112,8 @@ static inline int arch_cmpxchg_niai8(int *lock, int old, int new)
return expected == old;
}
#endif /* __HAVE_ASM_FLAG_OUTPUTS__ */
static inline struct spin_wait *arch_spin_decode_tail(int lock)
{
int ix, cpu;
@ -226,7 +246,7 @@ static inline void arch_spin_lock_classic(arch_spinlock_t *lp)
/* Try to get the lock if it is free. */
if (!owner) {
new = (old & _Q_TAIL_MASK) | lockval;
if (arch_cmpxchg_niai8(&lp->lock, old, new)) {
if (arch_try_cmpxchg_niai8(&lp->lock, old, new)) {
/* Got the lock */
return;
}