LXR linux/arch/x86/include/asm/vgtod.h

   1#ifndef _ASM_X86_VGTOD_H
   2#define _ASM_X86_VGTOD_H
   3
   4#include <linux/compiler.h>
   5#include <linux/clocksource.h>
   6
   7#ifdef BUILD_VDSO32_64
   8typedef u64 gtod_long_t;
   9#else
  10typedef unsigned long gtod_long_t;
  11#endif
  12/*
  13 * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
  14 * so be carefull by modifying this structure.
  15 */
  16struct vsyscall_gtod_data {
  17        unsigned seq;
  18
  19        int vclock_mode;
  20        u64     cycle_last;
  21        u64     mask;
  22        u32     mult;
  23        u32     shift;
  24
  25        /* open coded 'struct timespec' */
  26        u64             wall_time_snsec;
  27        gtod_long_t     wall_time_sec;
  28        gtod_long_t     monotonic_time_sec;
  29        u64             monotonic_time_snsec;
  30        gtod_long_t     wall_time_coarse_sec;
  31        gtod_long_t     wall_time_coarse_nsec;
  32        gtod_long_t     monotonic_time_coarse_sec;
  33        gtod_long_t     monotonic_time_coarse_nsec;
  34
  35        int             tz_minuteswest;
  36        int             tz_dsttime;
  37};
  38extern struct vsyscall_gtod_data vsyscall_gtod_data;
  39
  40extern int vclocks_used;
  41static inline bool vclock_was_used(int vclock)
  42{
  43        return READ_ONCE(vclocks_used) & (1 << vclock);
  44}
  45
  46static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
  47{
  48        unsigned ret;
  49
  50repeat:
  51        ret = ACCESS_ONCE(s->seq);
  52        if (unlikely(ret & 1)) {
  53                cpu_relax();
  54                goto repeat;
  55        }
  56        smp_rmb();
  57        return ret;
  58}
  59
  60static inline int gtod_read_retry(const struct vsyscall_gtod_data *s,
  61                                        unsigned start)
  62{
  63        smp_rmb();
  64        return unlikely(s->seq != start);
  65}
  66
  67static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
  68{
  69        ++s->seq;
  70        smp_wmb();
  71}
  72
  73static inline void gtod_write_end(struct vsyscall_gtod_data *s)
  74{
  75        smp_wmb();
  76        ++s->seq;
  77}
  78
  79#ifdef CONFIG_X86_64
  80
  81#define VGETCPU_CPU_MASK 0xfff
  82
  83static inline unsigned int __getcpu(void)
  84{
  85        unsigned int p;
  86
  87        /*
  88         * Load per CPU data from GDT.  LSL is faster than RDTSCP and
  89         * works on all CPUs.  This is volatile so that it orders
  90         * correctly wrt barrier() and to keep gcc from cleverly
  91         * hoisting it out of the calling function.
  92         *
  93         * If RDPID is available, use it.
  94         */
  95        alternative_io ("lsl %[p],%[seg]",
  96                        ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
  97                        X86_FEATURE_RDPID,
  98                        [p] "=a" (p), [seg] "r" (__PER_CPU_SEG));
  99
 100        return p;
 101}
 102
 103#endif /* CONFIG_X86_64 */
 104
 105#endif /* _ASM_X86_VGTOD_H */
 106