我需要能够从任何线程内部调用线程池的方法
这就要求线程池数据是互斥机制的,比如Mutex or RwLock (RefCell
不适合多线程情况,请参阅the book)。此外,每个线程必须保留对线程池数据的引用,因为线程池存储线程,这会创建一个problem。为了解决这个问题,我们可以将线程池数据放在一个Arc并存储一个Weak在每个线程中引用它。请注意,我们使用弱引用来避免参考周期.
这实际上最终会改变 1 个或多个线程(调用者和目标)。
这就要求线程数据采用互斥机制。要最终确定要求,请注意,由于线程池数据位于Mutex
,我们无法返回对线程的引用(这需要保持线程池数据锁定),因此我们还将线程数据放入Arc
.
这是使用的实现示例Mutex
(操场):
use std::collections::HashMap;
use std::sync::{Arc, Weak, Mutex};
type Id = u32;
struct ThreadPool {
inner: Arc<Mutex<ThreadPoolInner>>,
}
struct ThreadPoolInner {
pool: HashMap<Id, Arc<Mutex<ThreadInner>>>,
id_count: Id,
}
impl ThreadPool {
fn new() -> ThreadPool {
let inner = ThreadPoolInner {
pool: HashMap::new(),
id_count: 0,
};
ThreadPool { inner: Arc::new(Mutex::new(inner)) }
}
fn create(&self) -> Thread {
let mut inner = self.inner.lock().unwrap();
let thread = Thread {
inner: Arc::new(Mutex::new(ThreadInner {
id: inner.id_count,
pool: Arc::downgrade(&self.inner),
})),
};
inner.id_count += 1;
let id = inner.id_count;
inner.pool.insert(id, thread.inner.clone());
thread
}
fn get(&self, id: Id) -> Option<Thread> {
let inner = self.inner.lock().unwrap();
inner.pool.get(&id).map(|t| Thread { inner: t.clone() })
}
fn some_mut_method(&self) {
let _inner = self.inner.lock().unwrap();
println!("something with pool");
}
}
struct Thread {
inner: Arc<Mutex<ThreadInner>>,
}
impl Thread {
fn get_pool(&self) -> Option<ThreadPool> {
let inner = self.inner.lock().unwrap();
// pool is a weak reference, upgrate try to get an Arc from it
inner.pool.upgrade().map(|inner| ThreadPool { inner: inner })
}
fn some_mut_method(&self) {
if let Some(pool) = self.get_pool() {
pool.some_mut_method();
let _t2 = pool.get(2).unwrap();
println!("something with t2");
}
}
}
#[derive(Clone)]
struct ThreadInner {
id: Id,
pool: Weak<Mutex<ThreadPoolInner>>,
}
fn main() {
let pool = ThreadPool::new();
let t1 = pool.create();
let _t2 = pool.create();
t1.some_mut_method();
}