98 lines
3.1 KiB
Rust
98 lines
3.1 KiB
Rust
use core::sync::atomic::Ordering;
|
|
|
|
use arch;
|
|
use super::{contexts, Context, Status, CONTEXT_ID};
|
|
|
|
/// Switch to the next context
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// Do not call this while holding locks!
|
|
pub unsafe fn switch() -> bool {
|
|
use core::ops::DerefMut;
|
|
|
|
// Set the global lock to avoid the unsafe operations below from causing issues
|
|
while arch::context::CONTEXT_SWITCH_LOCK.compare_and_swap(false, true, Ordering::SeqCst) {
|
|
arch::interrupt::pause();
|
|
}
|
|
|
|
let cpu_id = ::cpu_id();
|
|
|
|
let from_ptr;
|
|
let mut to_ptr = 0 as *mut Context;
|
|
{
|
|
let contexts = contexts();
|
|
{
|
|
let context_lock = contexts.current().expect("context::switch: not inside of context");
|
|
let mut context = context_lock.write();
|
|
from_ptr = context.deref_mut() as *mut Context;
|
|
}
|
|
|
|
let check_context = |context: &mut Context| -> bool {
|
|
if context.cpu_id == None && cpu_id == 0 {
|
|
context.cpu_id = Some(cpu_id);
|
|
// println!("{}: take {} {}", cpu_id, context.id, ::core::str::from_utf8_unchecked(&context.name.lock()));
|
|
}
|
|
|
|
if context.status == Status::Blocked && context.wake.is_some() {
|
|
let wake = context.wake.expect("context::switch: wake not set");
|
|
|
|
let current = arch::time::monotonic();
|
|
if current.0 > wake.0 || (current.0 == wake.0 && current.1 >= wake.1) {
|
|
context.unblock();
|
|
}
|
|
}
|
|
|
|
if context.cpu_id == Some(cpu_id) {
|
|
if context.status == Status::Runnable && ! context.running {
|
|
return true;
|
|
}
|
|
}
|
|
|
|
false
|
|
};
|
|
|
|
for (pid, context_lock) in contexts.iter() {
|
|
if *pid > (*from_ptr).id {
|
|
let mut context = context_lock.write();
|
|
if check_context(&mut context) {
|
|
to_ptr = context.deref_mut() as *mut Context;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
if to_ptr as usize == 0 {
|
|
for (pid, context_lock) in contexts.iter() {
|
|
if *pid < (*from_ptr).id {
|
|
let mut context = context_lock.write();
|
|
if check_context(&mut context) {
|
|
to_ptr = context.deref_mut() as *mut Context;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
if to_ptr as usize == 0 {
|
|
// Unset global lock if no context found
|
|
arch::context::CONTEXT_SWITCH_LOCK.store(false, Ordering::SeqCst);
|
|
return false;
|
|
}
|
|
|
|
(&mut *from_ptr).running = false;
|
|
(&mut *to_ptr).running = true;
|
|
if let Some(ref stack) = (*to_ptr).kstack {
|
|
arch::gdt::TSS.rsp[0] = (stack.as_ptr() as usize + stack.len() - 256) as u64;
|
|
}
|
|
CONTEXT_ID.store((&mut *to_ptr).id, Ordering::SeqCst);
|
|
|
|
// Unset global lock before switch, as arch is only usable by the current CPU at this time
|
|
arch::context::CONTEXT_SWITCH_LOCK.store(false, Ordering::SeqCst);
|
|
|
|
(&mut *from_ptr).arch.switch_to(&mut (&mut *to_ptr).arch);
|
|
|
|
true
|
|
}
|