[英]How to “unlock” an RwLock?
我正在嘗試解決線程環問題。 在每個線程中,我讀取令牌值
如果不是我的,請檢查程序是否結束
如果它是我的(即具有我的ID),則獲取寫鎖,增加令牌的值,檢查是否為結尾,然后告訴主線程我完成了它並完成當前線程循環
如果還沒有結束,則釋放寫鎖,然后再次開始讀取
沒有解鎖。 有沒有我需要的解鎖功能?
似乎我也應該釋放讀取鎖,因為如果有人讀取數據,則不會發生寫入鎖。 有必要嗎?
fn main() {
use std::sync::{Arc, RwLock};
use std::thread;
use std::sync::mpsc::channel;
const N: usize = 5; //503;
const STOP_POINT: usize = 100;
let n = Arc::new(RwLock::new(1));
let (sender, reciever) = channel();
for i in 1..N {
let (n_c, channel) = (n.clone(), sender.clone());
// println!("Thread n.{} beeing created!", i);
let a = thread::Builder::new()
.name(i.to_string())
.spawn(move || -> () {
loop {
let mut read_only = n_c.read().unwrap();
let say_my_name = (*thread::current().name().unwrap()).to_string();
// println!("Thread {} says: gonna try!", say_my_name);
while (*read_only % N) != i {
if *read_only == 0 {
break;
}
// println!("Thread {} says: aint mine!", say_my_name);
read_only = n_c.read().unwrap();
} // WAIT
println!("Thread {} says: my turn!", say_my_name);
let mut ref_to_num = n_c.write().unwrap();
*ref_to_num += 1;
if *ref_to_num == STOP_POINT {
channel.send(say_my_name).unwrap();
break;
}
}
()
});
assert_eq!(a.is_ok(), true);
// thread::spawn();
// println!("Thread n.{} created!", i);
}
println!("{}", reciever.recv().unwrap());
}
要釋放鎖,請使其超出范圍或通過調用drop
顯式調用其析構函數。
這是在兩個地方使用drop
編寫程序的方式:
fn main() {
use std::sync::{Arc, RwLock};
use std::sync::mpsc::channel;
use std::thread;
use std::time::Duration;
const N: usize = 503;
const STOP_POINT: usize = 100;
let n = Arc::new(RwLock::new(1));
let (sender, receiver) = channel();
for i in 1..N {
let (n_c, channel) = (n.clone(), sender.clone());
// println!("Thread n.{} beeing created!", i);
thread::Builder::new()
.name(i.to_string())
.spawn(move || {
loop {
let mut read_only = n_c.read().unwrap();
let say_my_name = (*thread::current().name().unwrap()).to_string();
// println!("Thread {} says: gonna try!", say_my_name);
while (*read_only % N) != i {
if *read_only == 0 {
break;
}
drop(read_only); // release the lock before sleeping
// println!("Thread {} says: aint mine!", say_my_name);
thread::sleep(Duration::from_millis(1));
read_only = n_c.read().unwrap();
}
println!("Thread {} says: my turn!", say_my_name);
drop(read_only); // release the read lock before taking a write lock
let mut ref_to_num = n_c.write().unwrap();
*ref_to_num += 1;
if *ref_to_num == STOP_POINT {
channel.send(say_my_name).unwrap();
break;
}
}
})
.expect("failed to spawn a thread");
// println!("Thread n.{} created!", i);
}
println!("{}", receiver.recv().unwrap());
}
請注意,如果不在while
循環中重新分配read_lock
,則編譯器將給出錯誤消息,因為在調用drop(read_lock)
之后, read_lock
沒有保存有效值。 Rust可以使用暫時未初始化的局部變量,但當然,我們需要重新初始化它們,然后才能再次使用它們。
這是編寫線程的主循環以使用范圍替換drop
的方式:
loop {
let say_my_name = (*thread::current().name().unwrap()).to_string();
{
let mut read_only = n_c.read().unwrap();
// println!("Thread {} says: gonna try!", say_my_name);
while (*read_only % N) != i {
if *read_only == 0 {
break;
}
drop(read_only);
thread::sleep(Duration::from_millis(1));
// println!("Thread {} says: aint mine!", say_my_name);
read_only = n_c.read().unwrap();
}
println!("Thread {} says: my turn!", say_my_name);
} // read_only is dropped here
let mut ref_to_num = n_c.write().unwrap();
*ref_to_num += 1;
if *ref_to_num == STOP_POINT {
channel.send(say_my_name).unwrap();
break;
}
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.