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adding comments to scheduling code

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This commit is contained in:
Anton Lydike 2021-08-22 12:02:11 +02:00
parent 737a9a1cf3
commit 5dccd2dc80
1 changed files with 22 additions and 8 deletions
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30
kinclude/sched.c
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@ -7,15 +7,20 @@
// use memset provided in boot.S
extern void memset(int, void*, void*);
// this is the address where threads return to
// it's located in a seprate section at the end of the kernel
extern int thread_finalizer;
// scheduling data:
// process list, holds all active and some dead processes
ProcessControlBlock processes[PROCESS_COUNT];
// pointer to the currently scheduled process
ProcessControlBlock* current_process = NULL;
// timer variables to add kernel time back to the processes time slice
unsigned long long int scheduling_interrupted_start;
unsigned long long int next_interrupt_scheduled_for;
// this counter generates process ids
int next_process_id = 1;
// run the next process
void scheduler_run_next ()
{
current_process = scheduler_select_free();
@ -24,20 +29,30 @@ void scheduler_run_next ()
scheduler_switch_to(current_process);
}
// try to return to a process
void scheduler_try_return_to(ProcessControlBlock* pcb)
{
// if the process isn't ready, schedule a new one
if (pcb->status != PROC_RDY) {
scheduler_run_next();
} else {
dbgln("returning to process...", 23);
current_process = pcb;
// add time spent in ecall handler to the processes time slice
next_interrupt_scheduled_for = next_interrupt_scheduled_for + (read_time() - scheduling_interrupted_start);
write_mtimecmp(next_interrupt_scheduled_for);
scheduler_switch_to(current_process);
// if we want to return to the current process...
if (current_process == pcb) {
dbgln("returning to process...", 23);
// add time spent in ecall handler to the processes time slice
next_interrupt_scheduled_for = next_interrupt_scheduled_for + (read_time() - scheduling_interrupted_start);
write_mtimecmp(next_interrupt_scheduled_for);
scheduler_switch_to(current_process);
} else {
// otherwise set a new interrupt
set_next_interrupt();
current_process = pcb;
scheduler_switch_to(current_process);
}
}
}
// select a new process to run next
ProcessControlBlock* scheduler_select_free()
{
unsigned long long int mtime;
@ -58,7 +73,6 @@ ProcessControlBlock* scheduler_select_free()
if (pcb->status == PROC_WAIT_SLEEP) {
if (pcb->asleep_until < mtime) {
//TODO: set wakeup args!
return pcb;
}
timeout_available = true;