include/minix/spin.h

   1 /* Prototypes for condition spinning helper functions (part of libsys). */
   2 #ifndef _MINIX_SPIN_H
   3 #define _MINIX_SPIN_H
   4
   5 /* Opaque spin state structure. */
   6 typedef struct {
   7         int s_state;
   8         u32_t s_usecs;
   9         u64_t s_base_tsc;
  10         clock_t s_base_uptime;
  11         int s_timeout;
  12 } spin_t;
  13
  14 /* Functions. */
  15 void spin_init(spin_t *s, u32_t usecs);
  16 int spin_check(spin_t *s);
  17
  18 /* Macros. */
  19
  20 /* Execute a loop for at least 'u' microseconds, using spin object 's'.
  21  * The body of the loop is guaranteed to be executed at least once.
  22  */
  23 #define SPIN_FOR(s,u)                                                   \
  24         for (spin_init((s), (u)); spin_check((s)); )
  25
  26 /* Return whether spin object 's' timed out after a loop. */
  27 #define SPIN_TIMEOUT(s) ((s)->s_timeout)
  28
  29 /* Spin until the given condition becomes true, or 'u' microseconds expired.
  30  * The condition is guaranteed to be checked at least once.
  31  */
  32 #define SPIN_UNTIL(c,u) do {                                            \
  33         spin_t s;                                                       \
  34         SPIN_FOR(&s,(u))                                                \
  35                 if (c) break;                                           \
  36 } while (0)
  37
  38 #endif /* _MINIX_SPIN_H */