new: Rust版本的Mutex (#157)

kernel/src/include/bindings/wrapper.h

@@ -29,4 +29,5 @@
 #include <mm/mm.h>
 #include <mm/slab.h>
 #include <process/process.h>
-#include <sched/sched.h>
+#include <sched/sched.h>
+#include <time/sleep.h>

kernel/src/lib.rs

@@ -1,5 +1,6 @@
 #![no_std] // <1>
 #![no_main] // <1>
+#![feature(const_mut_refs)]
 #![feature(core_intrinsics)] // <2>
 #![feature(alloc_error_handler)]
 #![feature(panic_info_message)]

kernel/src/libs/mod.rs

@@ -6,4 +6,5 @@ pub mod refcount;
 pub mod atomic;
 pub mod list;
 pub mod lockref;
+pub mod mutex;
 pub mod wait_queue;

kernel/src/libs/mutex.rs

@@ -0,0 +1,169 @@
+use core::{
+    cell::UnsafeCell,
+    ops::{Deref, DerefMut},
+};
+
+use alloc::collections::LinkedList;
+
+use crate::{
+    arch::{asm::current::current_pcb, sched::sched},
+    include::bindings::bindings::{
+        pid_t, process_control_block, process_wakeup, EBUSY, PROC_INTERRUPTIBLE, PROC_RUNNING,
+    },
+    libs::spinlock::SpinLockGuard,
+};
+
+use super::spinlock::SpinLock;
+
+#[derive(Debug)]
+struct MutexInner {
+    /// 当前Mutex是否已经被上锁(上锁时，为true)
+    is_locked: bool,
+    /// 等待获得这个锁的进程的链表
+    wait_list: LinkedList<&'static mut process_control_block>,
+}
+
+/// @brief Mutex互斥量结构体
+/// 请注意！由于Mutex属于休眠锁，因此，如果您的代码可能在中断上下文内执行，请勿采用Mutex！
+#[derive(Debug)]
+pub struct Mutex<T> {
+    /// 该Mutex保护的数据
+    data: UnsafeCell<T>,
+    /// Mutex内部的信息
+    inner: SpinLock<MutexInner>,
+}
+
+/// @brief Mutex的守卫
+#[derive(Debug)]
+pub struct MutexGuard<'a, T: 'a> {
+    lock: &'a Mutex<T>,
+}
+
+unsafe impl<T> Sync for Mutex<T> where T: Send {}
+
+impl<T> Mutex<T> {
+    /// @brief 初始化一个新的Mutex对象
+    #[allow(dead_code)]
+    pub const fn new(value: T) -> Self {
+        return Self {
+            data: UnsafeCell::new(value),
+            inner: SpinLock::new(MutexInner {
+                is_locked: false,
+                wait_list: LinkedList::<&'static mut process_control_block>::new(),
+            }),
+        };
+    }
+
+    /// @brief 对Mutex加锁
+    /// @return MutexGuard<T> 返回Mutex的守卫，您可以使用这个守卫来操作被保护的数据
+    #[inline(always)]
+    #[allow(dead_code)]
+    pub fn lock(&self) -> MutexGuard<T> {
+        loop {
+            let mut inner: SpinLockGuard<MutexInner> = self.inner.lock();
+            // 当前mutex已经上锁
+            if inner.is_locked {
+                // 检查当前进程是否处于等待队列中,如果不在，就加到等待队列内
+                if self.check_pid_in_wait_list(&inner, current_pcb().pid) == false {
+                    inner.wait_list.push_back(current_pcb());
+                }
+
+                // 加到等待唤醒的队列，然后睡眠
+                drop(inner);
+                self.__sleep();
+            } else {
+                // 加锁成功
+                inner.is_locked = true;
+                drop(inner);
+                break;
+            }
+        }
+
+        // 加锁成功，返回一个守卫
+        return MutexGuard { lock: self };
+    }
+
+    /// @brief 尝试对Mutex加锁。如果加锁失败，不会将当前进程加入等待队列。
+    /// @return Ok 加锁成功，返回Mutex的守卫
+    /// @return Err 如果Mutex当前已经上锁，则返回Err.
+    #[inline(always)]
+    #[allow(dead_code)]
+    pub fn try_lock(&self) -> Result<MutexGuard<T>, i32> {
+        let mut inner = self.inner.lock();
+
+        // 如果当前mutex已经上锁，则失败
+        if inner.is_locked {
+            return Err(-(EBUSY as i32));
+        } else {
+            // 加锁成功
+            inner.is_locked = true;
+            return Ok(MutexGuard { lock: self });
+        }
+    }
+
+    /// @brief Mutex内部的睡眠函数
+    fn __sleep(&self) {
+        current_pcb().state &= !(PROC_RUNNING as u64);
+        current_pcb().state |= PROC_INTERRUPTIBLE as u64;
+        sched();
+    }
+
+    /// @brief 放锁。
+    ///
+    /// 本函数只能是私有的，且只能被守卫的drop方法调用，否则将无法保证并发安全。
+    fn unlock(&self) {
+        let mut inner: SpinLockGuard<MutexInner> = self.inner.lock();
+        // 当前mutex一定是已经加锁的状态
+        assert!(inner.is_locked);
+        // 标记mutex已经解锁
+        inner.is_locked = false;
+        if inner.wait_list.is_empty() {
+            return;
+        }
+
+        // wait_list不为空，则获取下一个要被唤醒的进程的pcb
+        let to_wakeup: &mut process_control_block = inner.wait_list.pop_front().unwrap();
+        drop(inner);
+
+        unsafe {
+            process_wakeup(to_wakeup);
+        }
+    }
+
+    /// @brief 检查进程是否在该mutex的等待队列内
+    #[inline]
+    fn check_pid_in_wait_list(&self, inner: &MutexInner, pid: pid_t) -> bool {
+        for p in inner.wait_list.iter() {
+            if p.pid == pid {
+                // 在等待队列内
+                return true;
+            }
+        }
+
+        // 不在等待队列内
+        return false;
+    }
+}
+
+/// 实现Deref trait，支持通过获取MutexGuard来获取临界区数据的不可变引用
+impl<T> Deref for MutexGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        return unsafe { &*self.lock.data.get() };
+    }
+}
+
+/// 实现DerefMut trait，支持通过获取MutexGuard来获取临界区数据的可变引用
+impl<T> DerefMut for MutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        return unsafe { &mut *self.lock.data.get() };
+    }
+}
+
+/// @brief 为MutexGuard实现Drop方法，那么，一旦守卫的生命周期结束，就会自动释放自旋锁，避免了忘记放锁的情况
+impl<T> Drop for MutexGuard<'_, T> {
+    fn drop(&mut self) {
+        self.lock.unlock();
+    }
+}