Commit 889221c4 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

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



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: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 84ac9658

arch/s390/lib/spinlock.c

+22 −2
Original line number Diff line number Diff line
@@ -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;

			}