#include <cpu/irq.h>
#include <cpu/power.h> // cpu_relax()
+#include <kern/proc_p.h> // proc_decQuantun()
+
/*
* Include platform-specific binding code if we're hosted.
* Try the CPU specific one for bare-metal environments.
* When the delay indicated by the timer expires, the timer
* device will execute the event associated with it.
*
+ * You should not call this function on an already running timer.
+ *
* \note Interrupt safe
*/
void timer_add(Timer *timer)
/**
* Wait for the specified amount of timer ticks.
+ *
+ * \note Sleeping while preemption is disabled fallbacks to a busy wait sleep.
*/
void timer_delayTicks(ticks_t delay)
{
/* We shouldn't sleep with interrupts disabled */
IRQ_ASSERT_ENABLED();
-#if defined(CONFIG_KERN_SIGNALS) && CONFIG_KERN_SIGNALS
+#if CONFIG_KERN_SIGNALS
Timer t;
-
- ASSERT(!sig_check(SIG_SINGLE));
- timer_setSignal(&t, proc_current(), SIG_SINGLE);
- timer_setDelay(&t, delay);
- timer_add(&t);
- sig_wait(SIG_SINGLE);
-
-#else /* !CONFIG_KERN_SIGNALS */
-
- ticks_t start = timer_clock();
-
- /* Busy wait */
- while (timer_clock() - start < delay)
- cpu_relax();
-
+ DB(t.magic = TIMER_MAGIC_INACTIVE;)
+ if (proc_preemptAllowed())
+ {
+ timer_setEvent(&t);
+ timer_setDelay(&t, delay);
+ timer_add(&t);
+ timer_waitEvent(&t);
+ }
+ else
#endif /* !CONFIG_KERN_SIGNALS */
+ {
+ ticks_t start = timer_clock();
+
+ /* Busy wait */
+ while (timer_clock() - start < delay)
+ cpu_relax();
+ }
}
hptime_t now, prev = timer_hw_hpread();
hptime_t delta;
- for(;;)
+ for (;;)
{
now = timer_hw_hpread();
/*
- * We rely on hptime_t being unsigned here to
- * reduce the modulo to an AND in the common
- * case of TIMER_HW_CNT.
+ * The timer counter may wrap here and "prev" can become
+ * greater than "now". So, be sure to always evaluate a
+ * coherent timer difference:
+ *
+ * 0 prev now TIMER_HW_CNT
+ * |_____|_______________|_____|
+ * ^^^^^^^^^^^^^^^
+ * delta = now - prev
+ *
+ * 0 now prev TIMER_HW_CNT
+ * |_____|_______________|_____|
+ * ^^^^^ ^^^^^
+ * delta = (TIMER_HW_CNT - prev) + now
+ *
+ * NOTE: TIMER_HW_CNT can be any value, not necessarily a power
+ * of 2. For this reason the "%" operator is not suitable for
+ * the generic case.
*/
- delta = (now - prev) % TIMER_HW_CNT;
+ delta = (now < prev) ? ((hptime_t)TIMER_HW_CNT - prev + now) :
+ (now - prev);
if (delta >= delay)
break;
delay -= delta;
}
#endif /* CONFIG_TIMER_UDELAY */
-
/**
* Timer interrupt handler. Find soft timers expired and
* trigger corresponding events.
TIMER_STROBE_ON;
- /* Perform hw IRQ handling */
- timer_hw_irq();
-
/* Update the master ms counter */
++_clock;
+ /* Update the current task's quantum (if enabled). */
+ proc_decQuantum();
+
#if CONFIG_TIMER_EVENTS
timer_poll(&timers_queue);
#endif
+ /* Perform hw IRQ handling */
+ timer_hw_irq();
+
TIMER_STROBE_OFF;
}