CONFIG_ARC_HAS_LLSC is not available for thedefaultarchitecture x86.
Result is shown for architecture arc

Insn: LLOCK/SCOND (efficient atomic ops)

configname: CONFIG_ARC_HAS_LLSC

Linux Kernel Configuration
└─>ARC Architecture Configuration
└─>ARC CPU Configuration
└─>Insn: LLOCK/SCOND (efficient atomic ops)
In linux kernel since version 3.1 (release Date: 2011-10-24)  
depends
NOT CONFIG_ARC_CANT_LLSC