root/arch/x86/lib/rwlock_64.S

/* Slow paths of read/write spinlocks. */

#include <linux/linkage.h>
#include <asm/rwlock.h>
#include <asm/alternative-asm.h>
#include <asm/dwarf2.h>

/* rdi: pointer to rwlock_t */
ENTRY(__write_lock_failed)
        CFI_STARTPROC
        LOCK_PREFIX
        addl $RW_LOCK_BIAS,(%rdi)
1:      rep
        nop
        cmpl $RW_LOCK_BIAS,(%rdi)
        jne 1b
        LOCK_PREFIX
        subl $RW_LOCK_BIAS,(%rdi)
        jnz  __write_lock_failed
        ret
        CFI_ENDPROC
END(__write_lock_failed)

/* rdi: pointer to rwlock_t */
ENTRY(__read_lock_failed)
        CFI_STARTPROC
        LOCK_PREFIX
        incl (%rdi)
1:      rep
        nop
        cmpl $1,(%rdi)
        js 1b
        LOCK_PREFIX
        decl (%rdi)
        js __read_lock_failed
        ret
        CFI_ENDPROC
END(__read_lock_failed)