root/arch/sparc/include/asm/vvar.h

INCLUDED FROM

DEFINITIONS

1. vvar_read_begin
2. vvar_read_retry
3. vvar_write_begin
4. vvar_write_end

   1 /*
   2  * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
   3  */
   4 
   5 #ifndef _ASM_SPARC_VVAR_DATA_H
   6 #define _ASM_SPARC_VVAR_DATA_H
   7 
   8 #include <asm/clocksource.h>
   9 #include <linux/seqlock.h>
  10 #include <linux/time.h>
  11 #include <linux/types.h>
  12 
  13 struct vvar_data {
  14         unsigned int seq;
  15 
  16         int vclock_mode;
  17         struct { /* extract of a clocksource struct */
  18                 u64     cycle_last;
  19                 u64     mask;
  20                 int     mult;
  21                 int     shift;
  22         } clock;
  23         /* open coded 'struct timespec' */
  24         u64             wall_time_sec;
  25         u64             wall_time_snsec;
  26         u64             monotonic_time_snsec;
  27         u64             monotonic_time_sec;
  28         u64             monotonic_time_coarse_sec;
  29         u64             monotonic_time_coarse_nsec;
  30         u64             wall_time_coarse_sec;
  31         u64             wall_time_coarse_nsec;
  32 
  33         int             tz_minuteswest;
  34         int             tz_dsttime;
  35 };
  36 
  37 extern struct vvar_data *vvar_data;
  38 extern int vdso_fix_stick;
  39 
  40 static inline unsigned int vvar_read_begin(const struct vvar_data *s)
  41 {
  42         unsigned int ret;
  43 
  44 repeat:
  45         ret = READ_ONCE(s->seq);
  46         if (unlikely(ret & 1)) {
  47                 cpu_relax();
  48                 goto repeat;
  49         }
  50         smp_rmb(); /* Finish all reads before we return seq */
  51         return ret;
  52 }
  53 
  54 static inline int vvar_read_retry(const struct vvar_data *s,
  55                                         unsigned int start)
  56 {
  57         smp_rmb(); /* Finish all reads before checking the value of seq */
  58         return unlikely(s->seq != start);
  59 }
  60 
  61 static inline void vvar_write_begin(struct vvar_data *s)
  62 {
  63         ++s->seq;
  64         smp_wmb(); /* Makes sure that increment of seq is reflected */
  65 }
  66 
  67 static inline void vvar_write_end(struct vvar_data *s)
  68 {
  69         smp_wmb(); /* Makes the value of seq current before we increment */
  70         ++s->seq;
  71 }
  72 
  73 
  74 #endif /* _ASM_SPARC_VVAR_DATA_H */