Struct wasm::rw_spinlock::RwSpinLock

pub struct RwSpinLock<T> {
    inner: UnsafeCell<T>,
    state: AtomicU32,
}

A spinlock based, read-write lock which favours writers over readers

Properties

• Read-write semantics allow for multiple readers at the same time, but require exclusive access for a writer
• Spin based, e.g. waiting for the lock wastes CPU cycles in a busy loop
  • This design however enables an implementation independent of operating system features like condition variables, the only requirement are 32 bit atomics in the ISA
• Biased towards writes: once a writer waits for the lock, all new reader wait until that writer got access

Fields

inner: UnsafeCell<T>

The inner data protected by this lock

state: AtomicU32

Lock state (on ambiguity, the state closer to the top takes precedence)

• 0 means there are no readers nor any writer
• u32::MAX means there is a single active writer
• state % 2 == 0 means there are state / 2 active readers
• state % 2 != 0 means there are (state - 1) / 2 active readers and at least one waiting writer

Implementations

impl<T> RwSpinLock<T>

pub fn new(value: T) -> Self

Create a new instance of self, wrapping the value of type T

pub fn read(&self) -> ReadLockGuard<'_, T>

pub fn write(&self) -> WriteLockGuard<'_, T>

Trait Implementations

impl<T> Sync for RwSpinLock<T>

where T: Send + Sync,