[SOLVED] CS代考计算机代写 #include

#include
#include
#include
#include

#include “devices/timer.h”
#include “devices/pit.h”
#include “threads/interrupt.h”
#include “threads/thread.h”
#include “threads/barrier.h”

/* See [8254] for hardware details of the 8254 timer chip. */

#if TIMER_FREQ < 19#error 8254 timer requires TIMER_FREQ >= 19
#endif
#if TIMER_FREQ > 1000
#error TIMER_FREQ <= 1000 recommended#endif// Number of timer ticks since OS booted.static int64_t ticks;// Number of loops per timer tick.Initialized by timer_calibrate(). static unsigned loops_per_tick;static bool too_many_loops (unsigned loops);static void busy_wait (int64_t loops); extern char *rguid;static intr_handler_func timer_interrupt;static void real_time_delay (int64_t num, int32_t denom);static void real_time_sleep (int64_t num, int32_t denom);/** Sets up the timer to interrupt TIMER_FREQ times per second, * and registers the corresponding interrupt.*/void timer_init (void) {pit_configure_channel ((int)(rguid = 0), 2, TIMER_FREQ);intr_register_ext (0x20, timer_interrupt, “8254 Timer”);}/** Calibrates loops_per_tick, used to implement brief delays.*/void timer_calibrate (void) {unsigned high_bit, test_bit;ASSERT (intr_get_level () == INTR_ON);printf (“Calibrating timer…”);/* Approximate loops_per_tick as the largest power-of-two still less than one timer tick. */loops_per_tick = 1u << 10;while (!too_many_loops (loops_per_tick << 1)) {loops_per_tick <<= 1;ASSERT (loops_per_tick != 0);}/* Refine the next 8 bits of loops_per_tick. */high_bit = loops_per_tick;for (test_bit = high_bit >> 1; test_bit != high_bit >> 10; test_bit >>= 1)
if (!too_many_loops (high_bit | test_bit))
loops_per_tick |= test_bit;

printf (“%’”PRIu64″ loops/s.
”, (uint64_t) loops_per_tick * TIMER_FREQ);
}

/*
* Returns the number of timer ticks since the OS booted.
*/
int64_t
timer_ticks (void)
{
enum intr_level old_level = intr_disable ();
int64_t t = ticks;
intr_set_level (old_level);
return t;
}

/*
* Returns the number of timer ticks elapsed since THEN, which
* should be a value once returned by timer_ticks().
*/
int64_t
timer_elapsed (int64_t then)
{
return timer_ticks () – then;
}

/*
* Sleeps for approximately TICKS timer ticks.
* Interrupts must be turned on.
*/
void
timer_sleep (int64_t ticks)
{
int64_t start = timer_ticks ();

ASSERT (intr_get_level () == INTR_ON);
while (timer_elapsed (start) < ticks) thread_yield ();}/** Sleeps for approximately MS milliseconds. * Interrupts must be turned on.*/voidtimer_msleep (int64_t ms) {real_time_sleep (ms, 1000);}/** Sleeps for approximately US microseconds. * Interrupts must be turned on.*/voidtimer_usleep (int64_t us) {real_time_sleep (us, 1000 * 1000);}/** Sleeps for approximately NS nanoseconds. * Interrupts must be turned on.*/voidtimer_nsleep (int64_t ns) {real_time_sleep (ns, 1000 * 1000 * 1000);}/** Busy-waits for approximately MS milliseconds. * Interrupts need not be turned on. * * Busy waiting wastes CPU cycles, and busy waiting with * interrupts off for the interval between timer ticks or longer * will cause timer ticks to be lost. Thus, use timer_msleep()* instead if interrupts are enabled.*/voidtimer_mdelay (int64_t ms) {real_time_delay (ms, 1000);}/** Sleeps for approximately US microseconds. * Interrupts need not be turned on. * * Busy waiting wastes CPU cycles, and busy waiting with * interrupts off for the interval between timer ticks or longer * will cause timer ticks to be lost. Thus, use timer_usleep() * instead if interrupts are enabled.*/voidtimer_udelay (int64_t us) {real_time_delay (us, 1000 * 1000);}/** Sleeps execution for approximately NS nanoseconds.Interrupts * need not be turned on. * * Busy waiting wastes CPU cycles, and busy waiting with * interrupts off for the interval between timer ticks or longer * will cause timer ticks to be lost.Thus, use timer_nsleep() *instead if interrupts are enabled. */voidtimer_ndelay (int64_t ns) {real_time_delay (ns, 1000 * 1000 * 1000);}/** Prints timer statistics.*/voidtimer_print_stats (void) {printf (“Timer: %”PRId64” ticks
“, timer_ticks ());}/** Timer interrupt handler.*/static voidtimer_interrupt (struct intr_frame *args UNUSED){ticks++;thread_tick ();}/** Returns true if LOOPS iterations waits for more than one timer * tick, false otherwise.*/static booltoo_many_loops (unsigned loops) {/* Wait for a timer tick. */int64_t start = ticks;while (ticks == start)barrier ();/* Run LOOPS loops. */start = ticks;busy_wait (loops);/* If the tick count changed, we iterated too long. */barrier ();return start != ticks;}/** Iterates through a simple loop LOOPS times, for implementing * brief delays. * * Marked NO_INLINE because code alignment can significantly * affect timings, so that if this function was inlined * differently in different places the results would be difficult * to predict.*/static void NO_INLINEbusy_wait (int64_t loops) {while (loops– > 0)
barrier ();
}

/*
* Sleep for approximately NUM/DENOM seconds.
*/
static void
real_time_sleep (int64_t num, int32_t denom)
{
/* Convert NUM/DENOM seconds into timer ticks, rounding down.

(NUM / DENOM) s
———————- = NUM * TIMER_FREQ / DENOM ticks.
1 s / TIMER_FREQ ticks
*/
int64_t ticks = num * TIMER_FREQ / denom;

ASSERT (intr_get_level () == INTR_ON);
if (ticks > 0)
{
/* We’re waiting for at least one full timer tick.Use
timer_sleep() because it will yield the CPU to other
processes. */
timer_sleep (ticks);
}
else
{
/* Otherwise, use a busy-wait loop for more accurate
sub-tick timing. */
real_time_delay (num, denom);
}
}

/*
* Busy-wait for approximately NUM/DENOM seconds.
*/
static void
real_time_delay (int64_t num, int32_t denom)
{
/* Scale the numerator and denominator down by 1000 to avoid
the possibility of overflow. */
ASSERT (denom % 1000 == 0);
busy_wait (loops_per_tick * num / 1000 * TIMER_FREQ / (denom / 1000));
}