src/devices/intq.h

   1 #ifndef DEVICES_INTQ_H
   2 #define DEVICES_INTQ_H
   3
   4 #include "threads/interrupt.h"
   5 #include "threads/synch.h"
   6
   7 /* An "interrupt queue", a circular buffer shared between
   8    kernel threads and external interrupt handlers.
   9
  10    Interrupt queue functions can be called from kernel threads or
  11    from external interrupt handlers.  Except for intq_init(),
  12    interrupts must be off in either case.
  13
  14    The interrupt queue has the structure of a "monitor".  Locks
  15    and condition variables from threads/synch.h cannot be used in
  16    this case, as they normally would, because they can only
  17    protect kernel threads from one another, not from interrupt
  18    handlers. */
  19
  20 /* Queue buffer size, in bytes. */
  21 #define INTQ_BUFSIZE 64
  22
  23 /* A circular queue of bytes. */
  24 struct intq
  25   {
  26     /* Waiting threads. */
  27     struct lock lock;           /* Only one thread may wait at once. */
  28     struct thread *not_full;    /* Thread waiting for not-full condition. */
  29     struct thread *not_empty;   /* Thread waiting for not-empty condition. */
  30
  31     /* Queue. */
  32     uint8_t buf[INTQ_BUFSIZE];  /* Buffer. */
  33     int head;                   /* New data is written here. */
  34     int tail;                   /* Old data is read here. */
  35   };
  36
  37 void intq_init (struct intq *);
  38 bool intq_empty (const struct intq *);
  39 bool intq_full (const struct intq *);
  40 uint8_t intq_getc (struct intq *);
  41 void intq_putc (struct intq *, uint8_t);
  42
  43 #endif /* devices/intq.h */