LXR linux/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#define read_barrier_depends()  do { } while (0)
  33
  34#ifdef CONFIG_SMP
  35
  36#define smp_mb()        mb()
  37#ifdef CONFIG_X86_PPRO_FENCE
  38#define smp_rmb()       rmb()
  39#else /* CONFIG_X86_PPRO_FENCE */
  40#define smp_rmb()       barrier()
  41#endif /* CONFIG_X86_PPRO_FENCE */
  42
  43#define smp_wmb()       barrier()
  44
  45#define smp_read_barrier_depends()      read_barrier_depends()
  46#define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
  47
  48#else /* CONFIG_SMP */
  49
  50#define smp_mb()        barrier()
  51#define smp_rmb()       barrier()
  52#define smp_wmb()       barrier()
  53#define smp_read_barrier_depends()      do { } while (0)
  54#define set_mb(var, value) do { var = value; barrier(); } while (0)
  55
  56#endif /* CONFIG_SMP */
  57
  58/*
  59 * Stop RDTSC speculation. This is needed when you need to use RDTSC
  60 * (or get_cycles or vread that possibly accesses the TSC) in a defined
  61 * code region.
  62 *
  63 * (Could use an alternative three way for this if there was one.)
  64 */
  65static inline void rdtsc_barrier(void)
  66{
  67        alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
  68        alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
  69}
  70
  71#endif
  72