From 9bddf55e9373ab337ece059448b0978ece778922 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jackpot51@gmail.com>
Date: Tue, 30 Aug 2016 16:23:51 -0600
Subject: [PATCH] Improvements for context switching
---
context/mod.rs | 47 ++++++++++++++++++++++++++++++++++++++++++++---
lib.rs | 26 ++++++++------------------
2 files changed, 52 insertions(+), 21 deletions(-)
diff --git a/context/mod.rs b/context/mod.rs
index 54877809..c7c02a88 100644
--- a/context/mod.rs
+++ b/context/mod.rs
@@ -6,6 +6,7 @@ use core::mem;
use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
+use arch;
use arch::context::Context as ArchContext;
use syscall::{Error, Result};
@@ -87,7 +88,8 @@ static CONTEXT_ID: AtomicUsize = ATOMIC_USIZE_INIT;
pub fn init() {
let mut contexts = contexts_mut();
let context_lock = contexts.new_context().expect("could not initialize first context");
- let context = context_lock.read();
+ let mut context = context_lock.write();
+ context.running = true;
CONTEXT_ID.store(context.id, Ordering::SeqCst);
}
@@ -108,8 +110,44 @@ pub fn contexts_mut() -> RwLockWriteGuard<'static, ContextList> {
/// Switch to the next context
/// Do not call this while holding locks!
-pub unsafe fn context_switch() {
-// current.arch.switch_to(&mut next.arch);
+pub unsafe fn switch() {
+ 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 from_ptr = if let Some(context_lock) = contexts().current() {
+ let mut context = context_lock.write();
+ context.deref_mut() as *mut Context
+ } else {
+ print!("NO FROM_PTR\n");
+ return;
+ };
+
+ let mut to_ptr = 0 as *mut Context;
+
+ for (_pid, context_lock) in contexts().map.iter() {
+ let mut context = context_lock.write();
+ if ! context.running {
+ to_ptr = context.deref_mut() as *mut Context;
+ break;
+ }
+ }
+
+ if to_ptr as usize == 0 {
+ print!("NO TO_PTR\n");
+ return;
+ }
+
+ unsafe {
+ (&mut *from_ptr).running = false;
+ (&mut *to_ptr).running = true;
+ CONTEXT_ID.store((&mut *to_ptr).id, Ordering::SeqCst);
+
+ (&mut *from_ptr).arch.switch_to(&mut (&mut *to_ptr).arch);
+ }
}
/// A context, which identifies either a process or a thread
@@ -117,6 +155,8 @@ pub unsafe fn context_switch() {
pub struct Context {
/// The ID of this context
pub id: usize,
+ /// Running or not
+ pub running: bool,
/// The architecture specific context
pub arch: ArchContext,
/// Kernel stack
@@ -130,6 +170,7 @@ impl Context {
pub fn new(id: usize) -> Context {
Context {
id: id,
+ running: false,
arch: ArchContext::new(),
kstack: None,
files: Vec::new()
diff --git a/lib.rs b/lib.rs
index acdf0288..cc032657 100644
--- a/lib.rs
+++ b/lib.rs
@@ -121,8 +121,10 @@ pub mod syscall;
pub mod tests;
pub extern fn context_test() {
- print!("TEST\n");
+ print!("Test\n");
+ unsafe { context::switch(); }
+ print!("Test halt\n");
loop {
unsafe { interrupt::enable_and_halt(); }
}
@@ -134,26 +136,14 @@ pub extern fn kmain() {
print!("{}", format!("BSP: {:?}\n", syscall::getpid()));
- let to_ptr = if let Ok(context_lock) = context::contexts_mut().spawn(context_test) {
+ if let Ok(context_lock) = context::contexts_mut().spawn(context_test) {
print!("Spawned context\n");
- let mut context = context_lock.write();
- &mut context.arch as *mut arch::context::Context
- } else {
- 0 as *mut arch::context::Context
- };
-
- let from_ptr = if let Some(context_lock) = context::contexts().current() {
- let mut context = context_lock.write();
- &mut context.arch as *mut arch::context::Context
- } else {
- 0 as *mut arch::context::Context
- };
-
- if to_ptr as usize != 0 && from_ptr as usize != 0 {
- print!("Switching\n");
- unsafe { (&mut *from_ptr).switch_to(&mut *to_ptr); }
}
+ print!("Main\n");
+ unsafe { context::switch(); }
+
+ print!("Main halt\n");
loop {
unsafe { interrupt::enable_and_halt(); }
}
--
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