ladybird/Kernel/TimerQueue.cpp
2021-06-25 19:26:30 +02:00

282 lines
8.7 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/NonnullOwnPtr.h>
#include <AK/Singleton.h>
#include <AK/Time.h>
#include <Kernel/Scheduler.h>
#include <Kernel/Sections.h>
#include <Kernel/Time/TimeManagement.h>
#include <Kernel/TimerQueue.h>
namespace Kernel {
static AK::Singleton<TimerQueue> s_the;
static SpinLock<u8> g_timerqueue_lock;
Time Timer::remaining() const
{
return m_remaining;
}
Time Timer::now(bool is_firing) const
{
// NOTE: If is_firing is true then TimePrecision::Precise isn't really useful here.
// We already have a quite precise time stamp because we just updated the time in the
// interrupt handler. In those cases, just use coarse timestamps.
auto clock_id = m_clock_id;
if (is_firing) {
switch (clock_id) {
case CLOCK_MONOTONIC:
clock_id = CLOCK_MONOTONIC_COARSE;
break;
case CLOCK_MONOTONIC_RAW:
// TODO: use a special CLOCK_MONOTONIC_RAW_COARSE like mechanism here
break;
case CLOCK_REALTIME:
clock_id = CLOCK_REALTIME_COARSE;
break;
default:
break;
}
}
return TimeManagement::the().current_time(clock_id);
}
TimerQueue& TimerQueue::the()
{
return *s_the;
}
UNMAP_AFTER_INIT TimerQueue::TimerQueue()
{
m_ticks_per_second = TimeManagement::the().ticks_per_second();
}
bool TimerQueue::add_timer_without_id(NonnullRefPtr<Timer> timer, clockid_t clock_id, const Time& deadline, Function<void()>&& callback)
{
if (deadline <= TimeManagement::the().current_time(clock_id))
return false;
// Because timer handlers can execute on any processor and there is
// a race between executing a timer handler and cancel_timer() this
// *must* be a RefPtr<Timer>. Otherwise calling cancel_timer() could
// inadvertently cancel another timer that has been created between
// returning from the timer handler and a call to cancel_timer().
timer->setup(clock_id, deadline, move(callback));
ScopedSpinLock lock(g_timerqueue_lock);
timer->m_id = 0; // Don't generate a timer id
add_timer_locked(move(timer));
return true;
}
TimerId TimerQueue::add_timer(NonnullRefPtr<Timer>&& timer)
{
ScopedSpinLock lock(g_timerqueue_lock);
timer->m_id = ++m_timer_id_count;
VERIFY(timer->m_id != 0); // wrapped
auto id = timer->m_id;
add_timer_locked(move(timer));
return id;
}
void TimerQueue::add_timer_locked(NonnullRefPtr<Timer> timer)
{
Time timer_expiration = timer->m_expires;
VERIFY(!timer->is_queued());
auto& queue = queue_for_timer(*timer);
if (queue.list.is_empty()) {
queue.list.append(timer.leak_ref());
queue.next_timer_due = timer_expiration;
} else {
Timer* following_timer = nullptr;
for (auto& t : queue.list) {
if (t.m_expires > timer_expiration) {
following_timer = &t;
break;
}
}
if (following_timer) {
bool next_timer_needs_update = queue.list.first() == following_timer;
queue.list.insert_before(*following_timer, timer.leak_ref());
if (next_timer_needs_update)
queue.next_timer_due = timer_expiration;
} else {
queue.list.append(timer.leak_ref());
}
}
}
TimerId TimerQueue::add_timer(clockid_t clock_id, const Time& deadline, Function<void()>&& callback)
{
auto expires = TimeManagement::the().current_time(clock_id);
expires = expires + deadline;
auto timer = new Timer();
VERIFY(timer);
timer->setup(clock_id, expires, move(callback));
return add_timer(adopt_ref(*timer));
}
bool TimerQueue::cancel_timer(TimerId id)
{
Timer* found_timer = nullptr;
Queue* timer_queue = nullptr;
ScopedSpinLock lock(g_timerqueue_lock);
for (auto& timer : m_timer_queue_monotonic.list) {
if (timer.m_id == id) {
found_timer = &timer;
timer_queue = &m_timer_queue_monotonic;
break;
}
}
if (found_timer == nullptr) {
for (auto& timer : m_timer_queue_realtime.list) {
if (timer.m_id == id) {
found_timer = &timer;
timer_queue = &m_timer_queue_realtime;
break;
}
};
}
if (!found_timer) {
// The timer may be executing right now, if it is then it should
// be in m_timers_executing. If it is then release the lock
// briefly to allow it to finish by removing itself
// NOTE: This can only happen with multiple processors!
while (true) {
for (auto& timer : m_timers_executing) {
if (timer.m_id == id) {
found_timer = &timer;
break;
}
}
if (found_timer) {
// NOTE: This isn't the most efficient way to wait, but
// it should only happen when multiple processors are used.
// Also, the timers should execute pretty quickly, so it
// should not loop here for very long. But we can't yield.
lock.unlock();
Processor::wait_check();
lock.lock();
found_timer = nullptr;
} else {
// We were not able to cancel the timer, but at this point
// the handler should have completed if it was running!
return false;
}
}
}
VERIFY(found_timer);
VERIFY(timer_queue);
remove_timer_locked(*timer_queue, *found_timer);
return true;
}
bool TimerQueue::cancel_timer(Timer& timer)
{
auto& timer_queue = queue_for_timer(timer);
ScopedSpinLock lock(g_timerqueue_lock);
if (!timer_queue.list.contains(timer)) {
// The timer may be executing right now, if it is then it should
// be in m_timers_executing. If it is then release the lock
// briefly to allow it to finish by removing itself
// NOTE: This can only happen with multiple processors!
while (m_timers_executing.contains(timer)) {
// NOTE: This isn't the most efficient way to wait, but
// it should only happen when multiple processors are used.
// Also, the timers should execute pretty quickly, so it
// should not loop here for very long. But we can't yield.
lock.unlock();
Processor::wait_check();
lock.lock();
}
// We were not able to cancel the timer, but at this point
// the handler should have completed if it was running!
return false;
}
VERIFY(timer.ref_count() > 1);
remove_timer_locked(timer_queue, timer);
return true;
}
void TimerQueue::remove_timer_locked(Queue& queue, Timer& timer)
{
bool was_next_timer = (queue.list.first() == &timer);
queue.list.remove(timer);
timer.set_queued(false);
auto now = timer.now(false);
if (timer.m_expires > now)
timer.m_remaining = timer.m_expires - now;
if (was_next_timer)
update_next_timer_due(queue);
// Whenever we remove a timer that was still queued (but hasn't been
// fired) we added a reference to it. So, when removing it from the
// queue we need to drop that reference.
timer.unref();
}
void TimerQueue::fire()
{
ScopedSpinLock lock(g_timerqueue_lock);
auto fire_timers = [&](Queue& queue) {
auto* timer = queue.list.first();
VERIFY(timer);
VERIFY(queue.next_timer_due == timer->m_expires);
while (timer && timer->now(true) > timer->m_expires) {
queue.list.remove(*timer);
timer->set_queued(false);
m_timers_executing.append(*timer);
update_next_timer_due(queue);
lock.unlock();
// Defer executing the timer outside of the irq handler
Processor::current().deferred_call_queue([this, timer]() {
timer->m_callback();
ScopedSpinLock lock(g_timerqueue_lock);
m_timers_executing.remove(*timer);
// Drop the reference we added when queueing the timer
timer->unref();
});
lock.lock();
timer = queue.list.first();
}
};
if (!m_timer_queue_monotonic.list.is_empty())
fire_timers(m_timer_queue_monotonic);
if (!m_timer_queue_realtime.list.is_empty())
fire_timers(m_timer_queue_realtime);
}
void TimerQueue::update_next_timer_due(Queue& queue)
{
VERIFY(g_timerqueue_lock.is_locked());
if (auto* next_timer = queue.list.first())
queue.next_timer_due = next_timer->m_expires;
else
queue.next_timer_due = {};
}
}