115 lines
2.7 KiB
C
115 lines
2.7 KiB
C
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#include "devices/intq.h"
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#include <debug.h>
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#include "threads/thread.h"
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static int next (int pos);
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static void wait (struct intq *q, struct thread **waiter);
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static void signal (struct intq *q, struct thread **waiter);
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/* Initializes interrupt queue Q. */
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void
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intq_init (struct intq *q)
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{
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lock_init (&q->lock);
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q->not_full = q->not_empty = NULL;
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q->head = q->tail = 0;
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}
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/* Returns true if Q is empty, false otherwise. */
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bool
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intq_empty (const struct intq *q)
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{
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ASSERT (intr_get_level () == INTR_OFF);
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return q->head == q->tail;
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}
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/* Returns true if Q is full, false otherwise. */
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bool
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intq_full (const struct intq *q)
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{
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ASSERT (intr_get_level () == INTR_OFF);
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return next (q->head) == q->tail;
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}
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/* Removes a byte from Q and returns it.
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If Q is empty, sleeps until a byte is added.
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When called from an interrupt handler, Q must not be empty. */
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uint8_t
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intq_getc (struct intq *q)
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{
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uint8_t byte;
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ASSERT (intr_get_level () == INTR_OFF);
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while (intq_empty (q))
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{
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ASSERT (!intr_context ());
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lock_acquire (&q->lock);
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wait (q, &q->not_empty);
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lock_release (&q->lock);
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}
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byte = q->buf[q->tail];
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q->tail = next (q->tail);
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signal (q, &q->not_full);
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return byte;
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}
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/* Adds BYTE to the end of Q.
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If Q is full, sleeps until a byte is removed.
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When called from an interrupt handler, Q must not be full. */
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void
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intq_putc (struct intq *q, uint8_t byte)
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{
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ASSERT (intr_get_level () == INTR_OFF);
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while (intq_full (q))
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{
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ASSERT (!intr_context ());
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lock_acquire (&q->lock);
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wait (q, &q->not_full);
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lock_release (&q->lock);
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}
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q->buf[q->head] = byte;
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q->head = next (q->head);
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signal (q, &q->not_empty);
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}
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/* Returns the position after POS within an intq. */
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static int
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next (int pos)
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{
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return (pos + 1) % INTQ_BUFSIZE;
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}
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/* WAITER must be the address of Q's not_empty or not_full
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member. Waits until the given condition is true. */
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static void
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wait (struct intq *q UNUSED, struct thread **waiter)
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{
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ASSERT (!intr_context ());
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ASSERT (intr_get_level () == INTR_OFF);
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ASSERT ((waiter == &q->not_empty && intq_empty (q))
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|| (waiter == &q->not_full && intq_full (q)));
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*waiter = thread_current ();
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thread_block ();
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}
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/* WAITER must be the address of Q's not_empty or not_full
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member, and the associated condition must be true. If a
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thread is waiting for the condition, wakes it up and resets
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the waiting thread. */
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static void
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signal (struct intq *q UNUSED, struct thread **waiter)
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{
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ASSERT (intr_get_level () == INTR_OFF);
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ASSERT ((waiter == &q->not_empty && !intq_empty (q))
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|| (waiter == &q->not_full && !intq_full (q)));
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if (*waiter != NULL)
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{
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thread_unblock (*waiter);
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*waiter = NULL;
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}
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}
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