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_SMP
  33
  34 #define smp_mb()        mb()
  35 #ifdef CONFIG_X86_PPRO_FENCE
  36 #define smp_rmb()       rmb()
  37 #else /* CONFIG_X86_PPRO_FENCE */
  38 #define smp_rmb()       barrier()
  39 #endif /* CONFIG_X86_PPRO_FENCE */
  40
  41 #define smp_wmb()       barrier()
  42
  43 #define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
  44
  45 #else /* CONFIG_SMP */
  46
  47 #define smp_mb()        barrier()
  48 #define smp_rmb()       barrier()
  49 #define smp_wmb()       barrier()
  50 #define set_mb(var, value) do { var = value; barrier(); } while (0)
  51
  52 #endif /* CONFIG_SMP */
  53
  54 #define read_barrier_depends()          do { } while (0)
  55 #define smp_read_barrier_depends()      do { } while (0)
  56
  57 /*
  58  * Stop RDTSC speculation. This is needed when you need to use RDTSC
  59  * (or get_cycles or vread that possibly accesses the TSC) in a defined
  60  * code region.
  61  *
  62  * (Could use an alternative three way for this if there was one.)
  63  */
  64 static inline void rdtsc_barrier(void)
  65 {
  66         alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
  67         alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
  68 }
  69
  70 #endif