lib/seqlock.h

   1 #ifndef FIO_SEQLOCK_H
   2 #define FIO_SEQLOCK_H
   3
   4 #include "../arch/arch.h"
   5
   6 struct seqlock {
   7         volatile int sequence;
   8 };
   9
  10 static inline void seqlock_init(struct seqlock *s)
  11 {
  12         s->sequence = 0;
  13 }
  14
  15 static inline unsigned int read_seqlock_begin(struct seqlock *s)
  16 {
  17         unsigned int seq;
  18
  19         do {
  20                 seq = s->sequence;
  21                 if (!(seq & 1))
  22                         break;
  23                 nop;
  24         } while (1);
  25
  26         read_barrier();
  27         return seq;
  28 }
  29
  30 static inline bool read_seqlock_retry(struct seqlock *s, unsigned int seq)
  31 {
  32         read_barrier();
  33         return s->sequence != seq;
  34 }
  35
  36 static inline void write_seqlock_begin(struct seqlock *s)
  37 {
  38         s->sequence++;
  39         write_barrier();
  40 }
  41
  42 static inline void write_seqlock_end(struct seqlock *s)
  43 {
  44         write_barrier();
  45         s->sequence++;
  46 }
  47
  48 #endif