Struct ReentrantLock

pub struct ReentrantLock<T: ?Sized> {
    mutex: Mutex,
    owner: Tid,
    lock_count: UnsafeCell<u32>,
    data: T,
}

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

A re-entrant mutual exclusion lock

This lock will block other threads waiting for the lock to become available. The thread which has already locked the mutex can lock it multiple times without blocking, preventing a common source of deadlocks.

Examples

Allow recursively calling a function needing synchronization from within a callback (this is how StdoutLock is currently implemented):

#![feature(reentrant_lock)]

use std::cell::RefCell;
use std::sync::ReentrantLock;

pub struct Log {
    data: RefCell<String>,
}

impl Log {
    pub fn append(&self, msg: &str) {
        self.data.borrow_mut().push_str(msg);
    }
}

static LOG: ReentrantLock<Log> = ReentrantLock::new(Log { data: RefCell::new(String::new()) });

pub fn with_log<R>(f: impl FnOnce(&Log) -> R) -> R {
    let log = LOG.lock();
    f(&*log)
}

with_log(|log| {
    log.append("Hello");
    with_log(|log| log.append(" there!"));
});

Fields

mutex: Mutex

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

owner: Tid

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

lock_count: UnsafeCell<u32>

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

data: T

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

Implementations

impl<T> ReentrantLock<T>

pub const fn new(t: T) -> ReentrantLock<T>

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

Creates a new re-entrant lock in an unlocked state ready for use.

Examples

#![feature(reentrant_lock)]
use std::sync::ReentrantLock;

let lock = ReentrantLock::new(0);

pub fn into_inner(self) -> T

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

Consumes this lock, returning the underlying data.

Examples

#![feature(reentrant_lock)]

use std::sync::ReentrantLock;

let lock = ReentrantLock::new(0);
assert_eq!(lock.into_inner(), 0);

impl<T: ?Sized> ReentrantLock<T>

pub fn lock(&self) -> ReentrantLockGuard<'_, T>

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

Acquires the lock, blocking the current thread until it is able to do so.

This function will block the caller until it is available to acquire the lock. Upon returning, the thread is the only thread with the lock held. When the thread calling this method already holds the lock, the call succeeds without blocking.

Examples

#![feature(reentrant_lock)]
use std::cell::Cell;
use std::sync::{Arc, ReentrantLock};
use std::thread;

let lock = Arc::new(ReentrantLock::new(Cell::new(0)));
let c_lock = Arc::clone(&lock);

thread::spawn(move || {
    c_lock.lock().set(10);
}).join().expect("thread::spawn failed");
assert_eq!(lock.lock().get(), 10);

pub fn get_mut(&mut self) -> &mut T

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

Returns a mutable reference to the underlying data.

Since this call borrows the ReentrantLock mutably, no actual locking needs to take place – the mutable borrow statically guarantees no locks exist.

Examples

#![feature(reentrant_lock)]
use std::sync::ReentrantLock;

let mut lock = ReentrantLock::new(0);
*lock.get_mut() = 10;
assert_eq!(*lock.lock(), 10);

#[doc(hidden)] pub fn try_lock(&self) -> Option<ReentrantLockGuard<'_, T>>

🔬This is a nightly-only experimental API. (std_internals)

Attempts to acquire this lock.

If the lock could not be acquired at this time, then None is returned. Otherwise, an RAII guard is returned.

This function does not block.

unsafe fn increment_lock_count(&self) -> Option<()>

🔬This is a nightly-only experimental API. (reentrant_lock #121440)

Trait Implementations

impl<T: Debug + ?Sized> Debug for ReentrantLock<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Default> Default for ReentrantLock<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T> From<T> for ReentrantLock<T>

fn from(t: T) -> Self

Converts to this type from the input type.

impl<T: RefUnwindSafe + ?Sized> RefUnwindSafe for ReentrantLock<T>

impl<T: Send + ?Sized> Send for ReentrantLock<T>

impl<T: Send + ?Sized> Sync for ReentrantLock<T>

impl<T: UnwindSafe + ?Sized> UnwindSafe for ReentrantLock<T>