lib/seqlock.h

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