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feat(runtime): Added comments for clarity

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minhtrannhat 2025-02-19 02:21:44 -05:00
parent b558986218
commit 7e5b38a890
Signed by: minhtrannhat
GPG Key ID: E13CFA85C53F8062
1 changed files with 46 additions and 5 deletions
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51
src/runtime.rs
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@ -12,7 +12,7 @@ pub static mut RUNTIME: usize = 0;
pub struct Runtime {
threads: Vec<Thread>,
current_thread: usize, // pointer to which thread we're running
current_thread: usize, // index of the thread we're running
}
/*
@ -56,6 +56,10 @@ impl Runtime {
// return function for when a thread is finished
fn t_return(&mut self) {
/* If it's not the base thread,
* we move the current thread state to Available
* and we yield the control to other threads
*/
if self.current_thread != 0 {
self.threads[self.current_thread].state = ThreadState::Available;
self.t_yield(); // yield control to other tasks
@ -73,27 +77,52 @@ impl Runtime {
*
* This is only a simple Round-Robin scheduler
*/
#[inline(never)] // rustc plz dont optimize
#[inline(never)] // rustc please do not inline everything
fn t_yield(&mut self) -> bool {
let mut pos = self.current_thread;
// going through all the threads that we have
// Going through all the threads that we have
while self.threads[pos].state != ThreadState::Ready {
pos += 1;
if pos == self.threads.len() {
pos = 0;
}
// No thread is Available
if pos == self.current_thread {
return false;
}
}
// we found at least one thread in READY state
/*
* Reaching here, it means that we've found one thread
* that is either Available or Running
*/
/*
* First case: the current thread was running
* but voluntarily gave up control to other
* threads, we put in READY mode
* to be scheduled to be returned later
*
* Here: pos != self.current_thread
*/
if self.threads[self.current_thread].state != ThreadState::Available {
self.threads[self.current_thread].state = ThreadState::Ready;
};
/*
* Second case: the current thread is already READY
* and want to be scheduled
*
* Here: pos == self.current_thread
*/
/*
* Here the code applies for both cases
*
* Second case means overhead when switching
*/
self.threads[pos].state = ThreadState::Running;
let old_pos = self.current_thread;
self.current_thread = pos;
@ -102,9 +131,21 @@ impl Runtime {
let old: *mut ThreadContext = &mut self.threads[old_pos].ctx;
let new: *const ThreadContext = &self.threads[pos].ctx;
/* We call the switch function with 2 parameters
*
* According to the System V x86_64 ABI,
* We have to put the first paramter into `rdi` register and
* second parameter into `rsi` parameter
*
* clobber_abi: also for System V x86_64 ABI
*/
asm!("call switch", in("rdi") old, in("rsi") new, clobber_abi("C"))
}
!self.threads.is_empty()
/* Code technically never reaches here
* since we already switch to a different thread
* via `call switch`
*/
self.threads.len() > 0
}
}