68 lines
1.9 KiB
C++
68 lines
1.9 KiB
C++
#include "./bellringer.h"
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#include "../arch/lapic.h"
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#include "../debug/assert.h"
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#include "../interrupt/guard.h"
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#include "arch/core_interrupt.h"
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// check: Checks whether bells are running out of time and rings them if
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// necessary
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void Bellringer::check(Vault &vault) {
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if (Bell *bell = bells.first()) {
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bell->counter--;
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while ((bell = bells.first()) && bell->counter == 0) {
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bells.dequeue();
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vault.scheduler.ready(bell->thread);
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}
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}
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}
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// job: Give a bell to the bellringer & ring it when the specified time ran out.
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void Bellringer::sleep(Vault &vault, unsigned int ms) {
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Bell bell_tmp;
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Bell *bell = &bell_tmp;
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bell->thread = vault.scheduler.active();
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assert(bell != nullptr);
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unsigned int ticks = ms * 1000 / LAPIC::Timer::interval();
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assert(ticks != 0);
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if (bells.first() == nullptr) {
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// queue is empty; enqueue new bell as first element
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bells.enqueue(*bell);
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} else {
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// To reduce the amount of work done in Bellringer::check (which
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// is called frequently), we sort the queue by relative waiting
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// times: Each bell is assigned the delta between its waiting
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// time and its predecessor's waiting time.
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// This allows us to only "tick" the first bell.
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Bell *next = nullptr;
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Bell *pred = nullptr;
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for (Bell *p = bells.first(); p != nullptr; p = bells.next(*p)) {
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if (ticks < p->counter) {
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next = p;
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break;
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}
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ticks -= p->counter;
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pred = p;
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}
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// If there is a predecessor, enqueue the bell after pred;
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// otherwise insert at the beginning.
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if (pred != nullptr) {
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bells.insertAfter(*pred, *bell);
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} else {
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bells.insertFirst(*bell);
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}
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// If we have a predecessor, reduce its waiting time by our waiting
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// time, as _next_ will have to wait until we finished waiting.
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if (next != nullptr) {
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next->counter -= ticks;
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}
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}
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bell->counter = ticks;
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vault.scheduler.resume(false);
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}
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// Are there bells in the queue?
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bool Bellringer::bellPending() const { return !bells.is_empty(); }
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