arch/x86/um/asm/barrier.h

   1 #ifndef _ASM_UM_BARRIER_H_
   2 #define _ASM_UM_BARRIER_H_
   3
   4 #include <asm/asm.h>
   5 #include <asm/segment.h>
   6 #include <asm/cpufeature.h>
   7 #include <asm/cmpxchg.h>
   8 #include <asm/nops.h>
   9
  10 #include <linux/kernel.h>
  11 #include <linux/irqflags.h>
  12
  13 /*
  14  * Force strict CPU ordering.
  15  * And yes, this is required on UP too when we're talking
  16  * to devices.
  17  */
  18 #ifdef CONFIG_X86_32
  19
  20 #define mb()    alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
  21 #define rmb()   alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
  22 #define wmb()   alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
  23
  24 #else /* CONFIG_X86_32 */
  25
  26 #define mb()    asm volatile("mfence" : : : "memory")
  27 #define rmb()   asm volatile("lfence" : : : "memory")
  28 #define wmb()   asm volatile("sfence" : : : "memory")
  29
  30 #endif /* CONFIG_X86_32 */
  31
  32 #ifdef CONFIG_X86_PPRO_FENCE
  33 #define dma_rmb()       rmb()
  34 #else /* CONFIG_X86_PPRO_FENCE */
  35 #define dma_rmb()       barrier()
  36 #endif /* CONFIG_X86_PPRO_FENCE */
  37 #define dma_wmb()       barrier()
  38
  39 #define smp_mb()        barrier()
  40 #define smp_rmb()       barrier()
  41 #define smp_wmb()       barrier()
  42
  43 #define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0)
  44
  45 #define read_barrier_depends()          do { } while (0)
  46 #define smp_read_barrier_depends()      do { } while (0)
  47
  48 /*
  49  * Stop RDTSC speculation. This is needed when you need to use RDTSC
  50  * (or get_cycles or vread that possibly accesses the TSC) in a defined
  51  * code region.
  52  *
  53  * (Could use an alternative three way for this if there was one.)
  54  */
  55 static inline void rdtsc_barrier(void)
  56 {
  57         alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
  58                           "lfence", X86_FEATURE_LFENCE_RDTSC);
  59 }
  60
  61 #endif