Added locking to the scheduler. Since this is invoked so often, it causes a race with the test_elf process.

risc_v/src/lock.rs

@@ -8,8 +8,8 @@ use crate::syscall::syscall_sleep;
 pub const DEFAULT_LOCK_SLEEP: usize = 10000;
 #[repr(u32)]
 pub enum MutexState {
-	Locked = 0,
-	Unlocked = 1,
+    Unlocked = 0,
+	Locked = 1,
 }
 
 #[repr(C)]
@@ -44,14 +44,14 @@ impl<'a> Mutex {
 	/// Never use a sleep lock for the process list. Sleeping requires
 	/// the process list to function, so you'll deadlock if you do.
 	pub fn sleep_lock(&mut self) {
-		while self.lock() == false {
+		while !self.lock() {
 			syscall_sleep(DEFAULT_LOCK_SLEEP);
 		}
 	}
 
 	/// Can safely be used inside of an interrupt context.
 	pub fn spin_lock(&mut self) {
-		while self.lock() == false {}
+		while !self.lock() {}
 	}
 
 	pub fn unlock(&mut self) {

risc_v/src/process.rs

@@ -59,7 +59,6 @@ pub fn set_running(pid: u16) -> bool {
 	// of process pointers.
 	let mut retval = false;
 	unsafe {
-		PROCESS_LIST_MUTEX.spin_lock();
 		if let Some(mut pl) = PROCESS_LIST.take() {
 			for proc in pl.iter_mut() {
 				if proc.pid == pid {
@@ -73,7 +72,6 @@ pub fn set_running(pid: u16) -> bool {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
-		PROCESS_LIST_MUTEX.unlock();
 	}
 	retval
 }
@@ -86,7 +84,6 @@ pub fn set_waiting(pid: u16) -> bool {
 	// of process pointers.
 	let mut retval = false;
 	unsafe {
-		PROCESS_LIST_MUTEX.spin_lock();
 		if let Some(mut pl) = PROCESS_LIST.take() {
 			for proc in pl.iter_mut() {
 				if proc.pid == pid {
@@ -100,7 +97,6 @@ pub fn set_waiting(pid: u16) -> bool {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
-		PROCESS_LIST_MUTEX.unlock();
 	}
 	retval
 }
@@ -111,7 +107,6 @@ pub fn set_sleeping(pid: u16, duration: usize) -> bool {
 	// of process pointers.
 	let mut retval = false;
 	unsafe {
-		PROCESS_LIST_MUTEX.spin_lock();
 		if let Some(mut pl) = PROCESS_LIST.take() {
 			for proc in pl.iter_mut() {
 				if proc.pid == pid {
@@ -129,7 +124,6 @@ pub fn set_sleeping(pid: u16, duration: usize) -> bool {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
-		PROCESS_LIST_MUTEX.unlock();
 	}
 	retval
 }
@@ -138,7 +132,6 @@ pub fn set_sleeping(pid: u16, duration: usize) -> bool {
 /// this function does nothing.
 pub fn delete_process(pid: u16) {
 	unsafe {
-		PROCESS_LIST_MUTEX.spin_lock();
 		if let Some(mut pl) = PROCESS_LIST.take() {
 			for i in 0..pl.len() {
 				let p = pl.get_mut(i).unwrap();
@@ -154,7 +147,6 @@ pub fn delete_process(pid: u16) {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
-		PROCESS_LIST_MUTEX.unlock();
 	}
 }
 
@@ -162,7 +154,6 @@ pub fn delete_process(pid: u16) {
 /// unsafe since the process can be deleted and we'll still have a pointer.
 pub unsafe fn get_by_pid(pid: u16) -> *mut Process {
 	let mut ret = null_mut();
-	PROCESS_LIST_MUTEX.spin_lock();
 	if let Some(mut pl) = PROCESS_LIST.take() {
 		for i in pl.iter_mut() {
 			if i.get_pid() == pid {
@@ -172,7 +163,6 @@ pub unsafe fn get_by_pid(pid: u16) -> *mut Process {
 		}
 		PROCESS_LIST.replace(pl);
 	}
-	PROCESS_LIST_MUTEX.unlock();
 	ret
 }
 
@@ -243,8 +233,6 @@ pub fn add_kernel_process(func: fn()) -> u16 {
 	// then move ownership back to the PROCESS_LIST.
 	// This allows mutual exclusion as anyone else trying to grab
 	// the process list will get None rather than the Deque.
-	unsafe { PROCESS_LIST_MUTEX.spin_lock(); } 
-	if let Some(mut pl) = unsafe { PROCESS_LIST.take() } {
 	// .take() will replace PROCESS_LIST with None and give
 	// us the only copy of the Deque.
 	let func_addr = func as usize;
@@ -286,15 +274,16 @@ pub fn add_kernel_process(func: fn()) -> u16 {
 		(*ret_proc.frame).mode = CpuMode::Machine as usize;
 		(*ret_proc.frame).pid = ret_proc.pid as usize;
 	}
+
+	if let Some(mut pl) = unsafe { PROCESS_LIST.take() } {
 		pl.push_back(ret_proc);
 		// Now, we no longer need the owned Deque, so we hand it
 		// back by replacing the PROCESS_LIST's None with the
 		// Some(pl).
 		unsafe {
 			PROCESS_LIST.replace(pl);
-			PROCESS_LIST_MUTEX.unlock();
 		}
-		return my_pid;
+		my_pid
 	}
 	else {
 		unsafe { PROCESS_LIST_MUTEX.unlock(); }
@@ -398,6 +387,7 @@ pub fn add_kernel_process_args(func: fn(args_ptr: usize), args: usize) -> u16 {
 /// but later, it should call the shell.
 pub fn init() -> usize {
 	unsafe {
+		PROCESS_LIST_MUTEX.spin_lock();
 		PROCESS_LIST = Some(VecDeque::with_capacity(15));
 		// add_process_default(init_process);
 		add_kernel_process(init_process);
@@ -412,6 +402,7 @@ pub fn init() -> usize {
 		// println!("Init's frame is at 0x{:08x}", frame);
 		// Put the process list back in the global.
 		PROCESS_LIST.replace(pl);
+		PROCESS_LIST_MUTEX.unlock();
 		// Return the first instruction's address to execute.
 		// Since we use the MMU, all start here.
 		(*p).pc

risc_v/src/sched.rs

@@ -3,12 +3,13 @@
 // Stephen Marz
 // 27 Dec 2019
 
-use crate::process::{ProcessState, PROCESS_LIST};
+use crate::process::{ProcessState, PROCESS_LIST, PROCESS_LIST_MUTEX};
 use crate::cpu::get_mtime;
 
 pub fn schedule() -> usize {
 	let mut frame_addr: usize = 0x1111;
 	unsafe {
+		PROCESS_LIST_MUTEX.spin_lock();
 		if let Some(mut pl) = PROCESS_LIST.take() {
 			// Rust allows us to label loops so that break statements can be
 			// targeted.
@@ -39,6 +40,7 @@ pub fn schedule() -> usize {
 		else {
 			println!("could not take process list");
 		}
+		PROCESS_LIST_MUTEX.unlock();
 	}
 	frame_addr
 }