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新增了rust实现的信号量 (#181)
* 新增了rust实现的信号量 --------- Co-authored-by: longjin <longjin@RinGoTek.cn>
This commit is contained in:
Gou Ngai
GitHub
parent
83b9512c1c
commit
f1284c3571
@ -9,3 +9,5 @@ pub mod lockref;
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pub mod mutex;
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pub mod semaphore;
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pub mod wait_queue;
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pub mod rwlock;
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447
kernel/src/libs/rwlock.rs
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447
kernel/src/libs/rwlock.rs
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@ -0,0 +1,447 @@
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#![allow(dead_code)]
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use core::{
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cell::UnsafeCell,
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hint::spin_loop,
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mem::{self, ManuallyDrop},
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ops::{Deref, DerefMut},
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sync::atomic::{AtomicU32, Ordering},
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};
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use crate::include::bindings::bindings::EOVERFLOW;
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///RwLock读写锁
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/// @brief READER位占据从右往左数第三个比特位
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const READER: u32 = 1 << 2;
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/// @brief UPGRADED位占据从右到左数第二个比特位
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const UPGRADED: u32 = 1 << 1;
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/// @brief WRITER位占据最右边的比特位
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const WRITER: u32 = 1;
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const READER_BIT: u32 = 2;
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/// @brief 读写锁的基本数据结构
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/// @param lock 32位原子变量,最右边的两位从左到右分别是UPGRADED,WRITER (标志位)
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/// 剩下的bit位存储READER数量(除了MSB)
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/// 对于标志位,0代表无, 1代表有
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/// 对于剩下的比特位表征READER的数量的多少
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/// lock的MSB必须为0,否则溢出
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#[derive(Debug)]
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pub struct RwLock<T> {
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lock: AtomicU32,
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data: UnsafeCell<T>,
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}
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/// @brief READER守卫的数据结构
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/// @param lock 是对RwLock的lock属性值的只读引用
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pub struct RwLockReadGuard<'a, T: 'a> {
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data: *const T,
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lock: &'a AtomicU32,
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}
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/// @brief UPGRADED是介于READER和WRITER之间的一种锁,它可以升级为WRITER,
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/// UPGRADED守卫的数据结构,注册UPGRADED锁只需要查看UPGRADED和WRITER的比特位
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/// 但是当UPGRADED守卫注册后,不允许有新的读者锁注册
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/// @param inner 是对RwLock数据结构的只读引用
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pub struct RwLockUpgradableGuard<'a, T: 'a> {
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data: *const T,
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inner: &'a RwLock<T>,
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}
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/// @brief WRITER守卫的数据结构
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/// @param data RwLock的data的可变引用
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/// @param inner 是对RwLock数据结构的只读引用
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pub struct RwLockWriteGuard<'a, T: 'a> {
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data: *mut T,
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inner: &'a RwLock<T>,
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}
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unsafe impl<T: Send> Send for RwLock<T> {}
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unsafe impl<T: Send + Sync> Sync for RwLock<T> {}
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/// @brief RwLock的API
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impl<T> RwLock<T> {
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#[inline]
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/// @brief RwLock的初始化
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pub const fn new(data: T) -> Self {
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return RwLock {
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lock: AtomicU32::new(0),
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data: UnsafeCell::new(data),
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};
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 将读写锁的皮扒掉,返回内在的data,返回的是一个真身而非引用
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pub fn into_inner(self) -> T {
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let RwLock { data, .. } = self;
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return data.into_inner();
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 返回data的raw pointer,
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/// unsafe
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pub fn as_mut_ptr(&self) -> *mut T {
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return self.data.get();
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 获取实时的读者数并尝试加1,如果增加值成功则返回增加1后的读者数,否则panic
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fn current_reader(&self) -> Result<u32, i32> {
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const MAX_READERS: u32 = core::u32::MAX >> READER_BIT >> 1; //右移3位
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let value = self.lock.fetch_add(READER, Ordering::Acquire);
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//value二进制形式的MSB不能为1, 否则导致溢出
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if value > MAX_READERS << READER_BIT {
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self.lock.fetch_sub(READER, Ordering::Release);
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//panic!("Too many lock readers, cannot safely proceed");
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return Err(-(EOVERFLOW as i32));
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} else {
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return Ok(value);
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 尝试获取READER守卫
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pub fn try_read(&self) -> Option<RwLockReadGuard<T>> {
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let reader_value = self.current_reader();
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//得到自增后的reader_value, 包括了尝试获得READER守卫的进程
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let value;
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if reader_value.is_err() {
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return None; //获取失败
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} else {
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value = reader_value.unwrap();
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}
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//判断有没有writer和upgrader
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//注意, 若upgrader存在,已经存在的读者继续占有锁,但新读者不允许获得锁
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if value & (WRITER | UPGRADED) != 0 {
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self.lock.fetch_sub(READER, Ordering::Release);
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return None;
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} else {
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return Some(RwLockReadGuard {
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data: unsafe { &*self.data.get() },
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lock: &self.lock,
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});
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 获得READER的守卫
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pub fn read(&self) -> RwLockReadGuard<T> {
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loop {
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match self.try_read() {
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Some(guard) => return guard,
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None => spin_loop(),
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}
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} //忙等待
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 获取读者+UPGRADER的数量, 不能保证能否获得同步值
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pub fn reader_count(&self) -> u32 {
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let state = self.lock.load(Ordering::Relaxed);
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return state / READER + (state & UPGRADED) / UPGRADED;
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 获取写者数量,不能保证能否获得同步值
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pub fn writer_count(&self) -> u32 {
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return (self.lock.load(Ordering::Relaxed) & WRITER) / WRITER;
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}
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#[cfg(target_arch = "x86_64")]
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#[allow(dead_code)]
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#[inline]
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/// @brief 尝试获得WRITER守卫
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pub fn try_write(&self) -> Option<RwLockWriteGuard<T>> {
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let res:bool = self
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.lock
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.compare_exchange(0, WRITER, Ordering::Acquire, Ordering::Relaxed).is_ok();
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//只有lock大小为0的时候能获得写者守卫
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if res {
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return Some(RwLockWriteGuard {
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data: unsafe { &mut *self.data.get() },
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inner: self,
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});
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} else {
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return None;
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}
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} //当架构为arm时,有些代码需要作出调整compare_exchange=>compare_exchange_weak
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#[allow(dead_code)]
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#[inline]
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/// @brief 获得WRITER守卫
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pub fn write(&self) -> RwLockWriteGuard<T> {
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loop {
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match self.try_write() {
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Some(guard) => return guard,
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None => spin_loop(),
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}
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 尝试获得UPGRADER守卫
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pub fn try_upgradeable_read(&self) -> Option<RwLockUpgradableGuard<T>> {
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//获得UPGRADER守卫不需要查看读者位
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//如果获得读者锁失败,不需要撤回fetch_or的原子操作
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if self.lock.fetch_or(UPGRADED, Ordering::Acquire) & (WRITER | UPGRADED) == 0 {
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return Some(RwLockUpgradableGuard {
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inner: self,
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data: unsafe { &mut *self.data.get() },
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});
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} else {
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return None;
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 获得UPGRADER守卫
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pub fn upgradeable_read(&self) -> RwLockUpgradableGuard<T> {
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loop {
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match self.try_upgradeable_read() {
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Some(guard) => return guard,
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None => spin_loop(),
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}
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}
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}
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#[allow(dead_code)]
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#[inline]
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//extremely unsafe behavior
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/// @brief 强制减少READER数
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pub unsafe fn force_read_decrement(&self) {
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debug_assert!(self.lock.load(Ordering::Relaxed) & !WRITER > 0);
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self.lock.fetch_sub(READER, Ordering::Release);
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}
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#[allow(dead_code)]
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#[inline]
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//extremely unsafe behavior
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/// @brief 强制给WRITER解锁
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pub unsafe fn force_write_unlock(&self) {
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debug_assert_eq!(self.lock.load(Ordering::Relaxed) & !(WRITER | UPGRADED), 0);
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self.lock.fetch_and(!(WRITER | UPGRADED), Ordering::Release);
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}
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#[allow(dead_code)]
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pub fn get_mut(&mut self) -> &mut T {
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unsafe { &mut *self.data.get() }
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}
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}
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impl<T: Default> Default for RwLock<T> {
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fn default() -> Self {
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Self::new(Default::default())
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}
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}
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/// @brief 由原有的值创建新的锁
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impl<T> From<T> for RwLock<T> {
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fn from(data: T) -> Self {
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return Self::new(data);
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}
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}
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impl<'rwlock, T> RwLockReadGuard<'rwlock, T> {
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#[allow(dead_code)]
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#[inline]
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/// @brief 释放守卫,获得保护的值的不可变引用
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pub fn leak(this: Self) -> &'rwlock T {
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let Self { data, .. } = this;
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return unsafe { &*data };
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}
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}
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impl<'rwlock, T> RwLockUpgradableGuard<'rwlock, T> {
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#[allow(dead_code)]
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#[inline]
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/// @brief 尝试将UPGRADER守卫升级为WRITER守卫
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pub fn try_upgrade(self) -> Result<RwLockWriteGuard<'rwlock, T>, Self> {
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let res = self.inner.lock.compare_exchange(
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UPGRADED,
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WRITER,
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Ordering::Acquire,
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Ordering::Relaxed,
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);
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//当且仅当只有UPGRADED守卫时可以升级
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if res.is_ok() {
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let inner = self.inner;
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mem::forget(self);
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Ok(RwLockWriteGuard {
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data: unsafe { &mut *inner.data.get() },
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inner,
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})
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} else {
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Err(self)
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 将upgrader升级成writer
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pub fn upgrade(mut self) -> RwLockWriteGuard<'rwlock, T> {
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loop {
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self = match self.try_upgrade() {
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Ok(writeguard) => return writeguard,
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Err(former) => former,
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};
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spin_loop();
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief UPGRADER降级为READER
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pub fn downgrade(self) -> RwLockReadGuard<'rwlock, T> {
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while self.inner.current_reader().is_err() {
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spin_loop();
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}
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let inner: &RwLock<T> = self.inner;
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//自动移去UPGRADED比特位
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mem::drop(self);
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RwLockReadGuard {
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data: unsafe { &*inner.data.get() },
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lock: &inner.lock,
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}
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 返回内部数据的引用,消除锁
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pub fn leak(this: Self) -> &'rwlock T {
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let this = ManuallyDrop::new(this);
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unsafe { &*this.data }
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}
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}
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impl<'rwlock, T> RwLockWriteGuard<'rwlock, T> {
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#[allow(dead_code)]
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#[inline]
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/// @brief 返回内部数据的引用,消除锁
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pub fn leak(this: Self) -> &'rwlock T {
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let this = ManuallyDrop::new(this);
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return unsafe { &*this.data };
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 将WRITER降级为READER
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pub fn downgrade(self) -> RwLockReadGuard<'rwlock, T> {
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while self.inner.current_reader().is_err() {
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spin_loop();
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}
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//本质上来说绝对保证没有任何读者
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let inner = self.inner;
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mem::drop(self);
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return RwLockReadGuard {
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data: unsafe { &*inner.data.get() },
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lock: &inner.lock,
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};
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}
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#[allow(dead_code)]
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#[inline]
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/// @brief 将WRITER降级为UPGRADER
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pub fn downgrade_to_upgradeable(self) -> RwLockUpgradableGuard<'rwlock, T> {
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debug_assert_eq!(
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self.inner.lock.load(Ordering::Acquire) & (WRITER | UPGRADED),
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WRITER
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);
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self.inner.lock.store(UPGRADED, Ordering::Release);
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let inner = self.inner;
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mem::forget(self);
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return RwLockUpgradableGuard {
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inner,
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data: unsafe { &*inner.data.get() },
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};
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}
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}
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impl<'rwlock, T> Deref for RwLockReadGuard<'rwlock, T> {
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type Target = T;
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fn deref(&self) -> &Self::Target {
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return unsafe { &*self.data };
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}
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}
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impl<'rwlock, T> Deref for RwLockUpgradableGuard<'rwlock, T> {
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type Target = T;
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fn deref(&self) -> &Self::Target {
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return unsafe { &*self.data };
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}
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}
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impl<'rwlock, T> Deref for RwLockWriteGuard<'rwlock, T> {
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type Target = T;
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fn deref(&self) -> &Self::Target {
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return unsafe { &*self.data };
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}
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}
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impl<'rwlock, T> DerefMut for RwLockWriteGuard<'rwlock, T> {
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fn deref_mut(&mut self) -> &mut Self::Target {
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return unsafe { &mut *self.data };
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}
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}
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impl<'rwlock, T> Drop for RwLockReadGuard<'rwlock, T> {
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fn drop(&mut self) {
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debug_assert!(self.lock.load(Ordering::Relaxed) & !(WRITER | UPGRADED) > 0);
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self.lock.fetch_sub(READER, Ordering::Release);
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}
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}
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impl<'rwlock, T> Drop for RwLockUpgradableGuard<'rwlock, T> {
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fn drop(&mut self) {
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debug_assert_eq!(
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self.inner.lock.load(Ordering::Relaxed) & (WRITER | UPGRADED),
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UPGRADED
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);
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self.inner.lock.fetch_sub(UPGRADED, Ordering::AcqRel);
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//这里为啥要AcqRel? Release应该就行了?
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}
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}
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impl<'rwlock, T> Drop for RwLockWriteGuard<'rwlock, T> {
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fn drop(&mut self) {
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debug_assert_eq!(self.inner.lock.load(Ordering::Relaxed) & WRITER, WRITER);
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self.inner
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.lock
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.fetch_and(!(WRITER | UPGRADED), Ordering::Release);
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}
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}
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