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 = atomic_load_acquire(&s->sequence);
  22                 if (!(seq & 1))
  23                         break;
  24                 nop;
  25         } while (1);
  26
  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 = atomic_load_acquire(&s->sequence) + 1;
  39 }
  40
  41 static inline void write_seqlock_end(struct seqlock *s)
  42 {
  43         atomic_store_release(&s->sequence, s->sequence + 1);
  44 }
  45
  46 #endif