Allow the frequency to be changed

kernel/include/scheduler.hpp

@@ -64,6 +64,11 @@ void queue_system_process(pid_t pid);
  */
 void queue_async_init_task(void (*fun)());
 
+/*!
+ * \brief Lets the scheduler know that the timer frequency has been updated
+ */
+void frequency_updated(uint64_t old_frequency, uint64_t new_frequency);
+
 } //end of namespace scheduler
 
 #endif

kernel/src/scheduler.cpp

@@ -953,3 +953,16 @@ void scheduler::queue_system_process(scheduler::pid_t pid){
 void scheduler::queue_async_init_task(void (*fun)()){
     init_tasks.emplace_back(fun);
 }
+
+void scheduler::frequency_updated(uint64_t old_frequency, uint64_t new_frequency){
+    // Cannot be interrupted during frequency update
+    direct_int_lock lock;
+
+    double ratio = old_frequency / double(new_frequency);
+
+    for(auto& process : pcb){
+        if(process.state == process_state::SLEEPING){
+            process.sleep_timeout *= ratio;
+        }
+    }
+}

kernel/src/timer.cpp

@@ -75,7 +75,11 @@ uint64_t timer::frequency(){
 }
 
 void timer::frequency(uint64_t freq){
+    auto old_frequency = _timer_frequency;
+
     _timer_frequency = freq;
 
     logging::logf(logging::log_level::DEBUG, "timer: Frequency set to %u Hz\n", freq);
+
+    scheduler::frequency_updated(old_frequency, _timer_frequency);
 }