Struct flexible_locks::Mutex
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pub struct Mutex<T: MutexProtected + ?Sized> { /* fields omitted */ }
A mutual exclusion primitive useful for protecting shared data
This mutex will block threads waiting for the lock to become available. The
mutex can be statically initialized via the [mutex_new
] macro, or created
via a new
constructor. Each mutex has a type parameter which represents
the data that it is protecting. The data can only be accessed through the
RAII guards returned from lock
, which guarantees that the data is only
ever accessed when the mutex is locked.
Differences from std::sync::Mutex
- No poisoning.
- No
try_lock
. - The underlying raw mutex primitive can be of any kind, within a
Box
or not, as long as theRawMutex
trait is implemented. Choose carefully. - The raw mutex primitive can be embedded anywhere in the data type. See
the [
MutexWrap
] type for a variant that looks more likestd::sync::Mutex
but still allows to use a specific raw mutex primitive. - With care, this can allow to share data through FFI and contend on the
same locks. See the
ffi-example
directory.
Examples
extern crate flexible_locks; #[macro_use] extern crate flexible_locks_derive; use flexible_locks::{Mutex, RawMutex}; // Pick your choice of raw mutex; #[cfg(windows)] use flexible_locks::SRWLOCK as RawOsMutex; #[cfg(unix)] use flexible_locks::pthread_mutex_t as RawOsMutex; use std::sync::Arc; use std::thread; use std::sync::mpsc::channel; #[derive(MutexProtected, Default)] struct Data { a: usize, b: usize, #[mutex] mutex: RawOsMutex, } const N: usize = 10; fn main() { // Spawn a few threads to increment a shared variable (non-atomically), // and let the main thread know once all increments are done. // // Here we're using an Arc to share memory among threads, and the data // inside the Arc is protected with a mutex. let data = Arc::new(Mutex::new(Data::default())); let (tx, rx) = channel(); for _ in 0..N { let (data, tx) = (data.clone(), tx.clone()); thread::spawn(move || { // The shared state can only be accessed once the lock is held. // Our non-atomic increment is safe because we're the only thread // which can access the shared state when the lock is held. let mut data = data.lock(); data.a += 1; if data.a == N { tx.send(()).unwrap(); } // the lock is unlocked here when `data` goes out of scope. }); } rx.recv().unwrap(); }
Please note that #[derive(MutexProtected)]
treats structs containing only
two fields including the raw mutex differently, such that the data handed
by [Mutex::lock
] is the non-mutex field, rather than the whole data.
In that case, it is preferable to use [MutexWrap
] instead.
See [MutexProtected::DataType
].
Methods
impl<T: MutexProtected> Mutex<T> where
T::DataType: Sized,
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T::DataType: Sized,
pub fn new(t: T) -> Self
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Creates a new mutex in an unlocked state ready for use.
Examples
#[macro_use] extern crate flexible_locks; #[macro_use] extern crate flexible_locks_derive; use flexible_locks::{Mutex, RawMutex}; // Pick your choice of raw mutex; #[cfg(windows)] use flexible_locks::SRWLOCK as RawOsMutex; #[cfg(unix)] use flexible_locks::pthread_mutex_t as RawOsMutex; #[derive(MutexProtected)] struct Data { a: usize, b: usize, #[mutex] mutex: RawOsMutex, } fn main() { let mutex = Mutex::new(Data { a: 2, b: 1, mutex: Default::default(), }); }
pub fn into_inner(self) -> T::DataType
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Consumes this mutex, returning the underlying data.
When the data type contains the raw mutex, which happens with
#[derive(MutexProtected)]
, the returned data obviously still
contains it. It is however in a destroyed state and may not be
reused.
Examples
#[macro_use] extern crate flexible_locks; #[macro_use] extern crate flexible_locks_derive; use flexible_locks::{Mutex, RawMutex}; // Pick your choice of raw mutex; #[cfg(windows)] use flexible_locks::SRWLOCK as RawOsMutex; #[cfg(unix)] use flexible_locks::pthread_mutex_t as RawOsMutex; #[derive(MutexProtected)] struct Data { a: usize, b: usize, #[mutex] mutex: RawOsMutex, } fn main() { let mutex = Mutex::new(Data { a: 2, b: 1, mutex: Default::default(), }); let data = mutex.into_inner(); assert_eq!(data.a, 2); assert_eq!(data.b, 1); }
impl<T: MutexProtected + ?Sized> Mutex<T>
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pub fn lock(&self) -> MutexGuard<T>
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Acquires a mutex, blocking the current thread until it is able to do so.
This function will block the local thread until it is available to acquire the mutex. Upon returning, the thread is the only thread with the lock held. An RAII guard is returned to allow scoped unlock of the lock. When the guard goes out of scope, the mutex will be unlocked.
The exact behavior on locking a mutex in the thread which already holds the lock depends on the underlying raw mutex implementation.
Examples
extern crate flexible_locks; #[macro_use] extern crate flexible_locks_derive; use flexible_locks::{Mutex, RawMutex}; // Pick your choice of raw mutex; #[cfg(windows)] use flexible_locks::SRWLOCK as RawOsMutex; #[cfg(unix)] use flexible_locks::pthread_mutex_t as RawOsMutex; use std::sync::Arc; use std::thread; #[derive(MutexProtected, Default)] struct Data { a: usize, b: usize, #[mutex] mutex: RawOsMutex, } fn main() { let mutex = Arc::new(Mutex::new(Data::default())); let c_mutex = mutex.clone(); thread::spawn(move || { c_mutex.lock().a = 10; }).join().expect("thread::spawn failed"); assert_eq!(mutex.lock().a, 10); }
pub fn get_mut(&mut self) -> &mut T::DataType
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Returns a mutable reference to the underlying data.
Since this call borrows the Mutex
mutably, no actual locking needs to
take place---the mutable borrow statically guarantees no locks exist.
Examples
extern crate flexible_locks; #[macro_use] extern crate flexible_locks_derive; use flexible_locks::{Mutex, RawMutex}; // Pick your choice of raw mutex; #[cfg(windows)] use flexible_locks::SRWLOCK as RawOsMutex; #[cfg(unix)] use flexible_locks::pthread_mutex_t as RawOsMutex; #[derive(MutexProtected, Default)] struct Data { a: usize, b: usize, #[mutex] mutex: RawOsMutex, } fn main() { let mut mutex = Mutex::new(Data::default()); mutex.get_mut().a = 10; assert_eq!(mutex.lock().a, 10); }
Trait Implementations
impl<T: MutexProtected + ?Sized + Send> Send for Mutex<T>
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impl<T: MutexProtected + ?Sized + Send> Sync for Mutex<T>
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impl<T: MutexProtected> From<T> for Mutex<T> where
T::DataType: Sized,
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T::DataType: Sized,