git.sesse.net Git - bcachefs-tools-debian/blob - c_src/include/linux/seqlock.h

   1 #ifndef __LINUX_SEQLOCK_H
   2 #define __LINUX_SEQLOCK_H
   3
   4 #include <linux/compiler.h>
   5
   6 typedef struct seqcount {
   7         unsigned sequence;
   8 } seqcount_t;
   9
  10 static inline void seqcount_init(seqcount_t *s)
  11 {
  12         s->sequence = 0;
  13 }
  14
  15 static inline unsigned read_seqcount_begin(const seqcount_t *s)
  16 {
  17         unsigned ret;
  18
  19 repeat:
  20         ret = READ_ONCE(s->sequence);
  21         if (unlikely(ret & 1)) {
  22                 cpu_relax();
  23                 goto repeat;
  24         }
  25         smp_rmb();
  26         return ret;
  27 }
  28
  29 static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
  30 {
  31         smp_rmb();
  32         return unlikely(s->sequence != start);
  33 }
  34
  35 static inline void write_seqcount_begin(seqcount_t *s)
  36 {
  37         s->sequence++;
  38         smp_wmb();
  39 }
  40
  41 static inline void write_seqcount_end(seqcount_t *s)
  42 {
  43         smp_wmb();
  44         s->sequence++;
  45 }
  46
  47 #endif /* __LINUX_SEQLOCK_H */