68 lines
2.1 KiB
Rust
68 lines
2.1 KiB
Rust
use core::sync::atomic::Ordering;
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use arch;
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use super::{contexts, Context, Status, CONTEXT_ID};
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/// Switch to the next context
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///
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/// # Safety
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///
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/// Do not call this while holding locks!
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pub unsafe fn switch() {
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use core::ops::DerefMut;
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// Set the global lock to avoid the unsafe operations below from causing issues
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while arch::context::CONTEXT_SWITCH_LOCK.compare_and_swap(false, true, Ordering::SeqCst) {
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arch::interrupt::pause();
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}
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let from_ptr = {
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let contexts = contexts();
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let context_lock = contexts.current().expect("context::switch: Not inside of context");
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let mut context = context_lock.write();
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context.deref_mut() as *mut Context
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};
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let mut to_ptr = 0 as *mut Context;
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for (pid, context_lock) in contexts().iter() {
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if *pid > (*from_ptr).id {
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let mut context = context_lock.write();
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if context.status == Status::Runnable && ! context.running {
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to_ptr = context.deref_mut() as *mut Context;
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break;
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}
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}
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}
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if to_ptr as usize == 0 {
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for (pid, context_lock) in contexts().iter() {
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if *pid < (*from_ptr).id {
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let mut context = context_lock.write();
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if context.status == Status::Runnable && ! context.running {
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to_ptr = context.deref_mut() as *mut Context;
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break;
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}
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}
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}
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}
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if to_ptr as usize == 0 {
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// TODO: Sleep, wait for interrupt
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// Unset global lock if no context found
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arch::context::CONTEXT_SWITCH_LOCK.store(false, Ordering::SeqCst);
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return;
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}
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//println!("Switch {} to {}", (&*from_ptr).id, (&*to_ptr).id);
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(&mut *from_ptr).running = false;
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(&mut *to_ptr).running = true;
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if let Some(ref stack) = (*to_ptr).kstack {
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arch::gdt::TSS.rsp[0] = (stack.as_ptr() as usize + stack.len() - 256) as u64;
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}
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CONTEXT_ID.store((&mut *to_ptr).id, Ordering::SeqCst);
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(&mut *from_ptr).arch.switch_to(&mut (&mut *to_ptr).arch);
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}
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