Add Mutex to process list.

risc_v/src/lock.rs

@@ -0,0 +1,57 @@
+// lock.rs
+// Locking routines
+// Stephen Marz
+// 26 Apr 2020
+
+use crate::syscall::syscall_sleep;
+
+pub const DEFAULT_LOCK_SLEEP: usize = 10000;
+#[repr(u32)]
+pub enum MutexState {
+	Locked = 0,
+	Unlocked = 1,
+}
+
+#[repr(C)]
+pub struct Mutex {
+	state: MutexState,
+}
+
+impl<'a> Mutex {
+	pub const fn new() -> Self {
+		Self { state: MutexState::Unlocked, }
+	}
+
+	pub fn val(&'a self) -> &'a MutexState {
+		&self.state
+	}
+
+	pub fn lock(&mut self) -> bool {
+		unsafe {
+			let ret: MutexState;
+			llvm_asm!("amoswap.w.aq $0, $1, ($2)\n" : "=r"(ret) : "r"(1), "r"(self) :: "volatile");
+			match ret {
+                MutexState::Locked => { false },
+				MutexState::Unlocked => true,
+			}
+		}
+	}
+
+    /// Do NOT sleep lock inside of an interrupt context!
+	pub fn sleep_lock(&mut self) {
+        while self.lock() == false {
+            syscall_sleep(DEFAULT_LOCK_SLEEP);
+        }
+	}
+
+    /// Can safely be used inside of an interrupt context.
+    pub fn spin_lock(&mut self) {
+        while self.lock() == false {}
+    }
+
+	pub fn unlock(&mut self) {
+		unsafe {
+			llvm_asm!("amoswap.w.rl zero, zero, ($0)" :: "r"(self) :: "volatile");
+		}
+	}
+}

risc_v/src/main.rs

@@ -179,6 +179,7 @@ pub mod cpu;
 pub mod elf;
 pub mod fs;
 pub mod kmem;
+pub mod lock;
 pub mod minixfs;
 pub mod page;
 pub mod plic;

risc_v/src/process.rs

@@ -20,6 +20,7 @@ use crate::{cpu::{build_satp,
             syscall::syscall_exit};
 use alloc::collections::vec_deque::VecDeque;
 use core::ptr::null_mut;
+use crate::lock::Mutex;
 
 // How many pages are we going to give a process for their
 // stack?
@@ -41,6 +42,7 @@ pub const PROCESS_STARTING_ADDR: usize = 0x2000_0000;
 // a VecDeque at compile time, so we are somewhat forced to
 // do this.
 pub static mut PROCESS_LIST: Option<VecDeque<Process>> = None;
+pub static mut PROCESS_LIST_MUTEX: Mutex = Mutex::new();
 // We can search through the process list to get a new PID, but
 // it's probably easier and faster just to increase the pid:
 pub static mut NEXT_PID: u16 = 1;
@@ -57,6 +59,7 @@ 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 {
@@ -70,6 +73,7 @@ pub fn set_running(pid: u16) -> bool {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
+		PROCESS_LIST_MUTEX.unlock();
 	}
 	retval
 }
@@ -82,6 +86,7 @@ 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 {
@@ -95,6 +100,7 @@ pub fn set_waiting(pid: u16) -> bool {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
+		PROCESS_LIST_MUTEX.unlock();
 	}
 	retval
 }
@@ -105,6 +111,7 @@ 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 {
@@ -122,6 +129,7 @@ pub fn set_sleeping(pid: u16, duration: usize) -> bool {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
+		PROCESS_LIST_MUTEX.unlock();
 	}
 	retval
 }
@@ -130,6 +138,7 @@ 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();
@@ -145,6 +154,7 @@ pub fn delete_process(pid: u16) {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
+		PROCESS_LIST_MUTEX.unlock();
 	}
 }
 
@@ -152,6 +162,7 @@ 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 {
@@ -161,7 +172,7 @@ pub unsafe fn get_by_pid(pid: u16) -> *mut Process {
 		}
 		PROCESS_LIST.replace(pl);
 	}
-
+	PROCESS_LIST_MUTEX.unlock();
 	ret
 }
 
@@ -203,6 +214,7 @@ pub fn add_process_default(pr: fn()) {
 		// 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.
+		PROCESS_LIST_MUTEX.spin_lock();
 		if let Some(mut pl) = PROCESS_LIST.take() {
 			// .take() will replace PROCESS_LIST with None and give
 			// us the only copy of the Deque.
@@ -213,6 +225,7 @@ pub fn add_process_default(pr: fn()) {
 			// Some(pl).
 			PROCESS_LIST.replace(pl);
 		}
+		PROCESS_LIST_MUTEX.unlock();
 		// TODO: When we get to multi-hart processing, we need to keep
 		// trying to grab the process list. We can do this with an
 		// atomic instruction. but right now, we're a single-processor
@@ -230,6 +243,7 @@ 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.
@@ -278,10 +292,12 @@ pub fn add_kernel_process(func: fn()) -> u16 {
 		// Some(pl).
 		unsafe {
 			PROCESS_LIST.replace(pl);
+			PROCESS_LIST_MUTEX.unlock();
 		}
-		my_pid
+		return my_pid;
 	}
 	else {
+		unsafe { PROCESS_LIST_MUTEX.unlock(); }
 		// TODO: When we get to multi-hart processing, we need to keep
 		// trying to grab the process list. We can do this with an
 		// atomic instruction. but right now, we're a single-processor
@@ -311,6 +327,7 @@ pub fn add_kernel_process_args(func: fn(args_ptr: usize), args: usize) -> 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.
@@ -360,10 +377,14 @@ pub fn add_kernel_process_args(func: fn(args_ptr: usize), args: usize) -> u16 {
 		// Some(pl).
 		unsafe {
 			PROCESS_LIST.replace(pl);
+			PROCESS_LIST_MUTEX.unlock();
 		}
 		my_pid
 	}
 	else {
+		unsafe {
+			PROCESS_LIST_MUTEX.unlock();
+		}
 		// TODO: When we get to multi-hart processing, we need to keep
 		// trying to grab the process list. We can do this with an
 		// atomic instruction. but right now, we're a single-processor

risc_v/src/syscall.rs

@@ -180,6 +180,10 @@ pub fn syscall_block_read(dev: usize,
 	) as u8
 }
 
+pub fn syscall_sleep(duration: usize)
+{
+	let _ = do_make_syscall(10, duration, 0, 0, 0, 0, 0);
+}
 // These system call numbers come from libgloss so that we can use newlib
 // for our system calls.
 // Libgloss wants the system call number in A7 and arguments in A0..A6

risc_v/src/test.rs

@@ -14,6 +14,7 @@ use crate::{cpu::{build_satp,
                       ProcessState,
                       NEXT_PID,
 					  PROCESS_LIST,
+					  PROCESS_LIST_MUTEX,
                       STACK_ADDR,
                       STACK_PAGES},
             syscall::syscall_fs_read};
@@ -189,6 +190,9 @@ pub fn test_elf() {
 	// I took a different tact here than in process.rs. In there I created
 	// the process while holding onto the process list. It might
 	// matter since this is asynchronous--it is being ran as a kernel process.
+	unsafe {
+		PROCESS_LIST_MUTEX.spin_lock();
+	}
 	if let Some(mut pl) = unsafe { PROCESS_LIST.take() } {
 		// As soon as we push this process on the list, it'll be
 		// schedule-able.
@@ -207,6 +211,9 @@ pub fn test_elf() {
 		// will be dropped and all of the associated allocations
 		// will be deallocated through the process' Drop trait.
 	}
+	unsafe {
+		PROCESS_LIST_MUTEX.unlock();
+	}
 	println!();
 }