text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef _ASM_UM_BARRIER_H_
  #define _ASM_UM_BARRIER_H_
  
  #include <asm/asm.h>
  #include <asm/segment.h>
  #include <asm/cpufeatures.h>
  #include <asm/cmpxchg.h>
  #include <asm/nops.h>
  
  #include <linux/kernel.h>
  #include <linux/irqflags.h>
  
  /*
   * Force strict CPU ordering.
   * And yes, this is required on UP too when we're talking
   * to devices.
   */
  #ifdef CONFIG_X86_32
  
  #define mb()	alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
  #define rmb()	alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
  #define wmb()	alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
  
  #else /* CONFIG_X86_32 */
  
  #define mb()	asm volatile("mfence" : : : "memory")
  #define rmb()	asm volatile("lfence" : : : "memory")
  #define wmb()	asm volatile("sfence" : : : "memory")
  
  #endif /* CONFIG_X86_32 */
  
  #ifdef CONFIG_X86_PPRO_FENCE
  #define dma_rmb()	rmb()
  #else /* CONFIG_X86_PPRO_FENCE */
  #define dma_rmb()	barrier()
  #endif /* CONFIG_X86_PPRO_FENCE */
  #define dma_wmb()	barrier()
  
  #include <asm-generic/barrier.h>
  
  #endif
  