Trait frame_support::dispatch::marker::Sync

#[lang = "sync"]pub unsafe auto trait Sync { }

Types for which it is safe to share references between threads.

This trait is automatically implemented when the compiler determines it's appropriate.

The precise definition is: a type T is Sync if and only if &T is Send. In other words, if there is no possibility of undefined behavior (including data races) when passing &T references between threads.

As one would expect, primitive types like u8 and f64 are all Sync, and so are simple aggregate types containing them, like tuples, structs and enums. More examples of basic Sync types include "immutable" types like &T, and those with simple inherited mutability, such as Box<T>, Vec<T> and most other collection types. (Generic parameters need to be Sync for their container to be Sync.)

A somewhat surprising consequence of the definition is that &mut T is Sync (if T is Sync) even though it seems like that might provide unsynchronized mutation. The trick is that a mutable reference behind a shared reference (that is, & &mut T) becomes read-only, as if it were a & &T. Hence there is no risk of a data race.

Types that are not Sync are those that have "interior mutability" in a non-thread-safe form, such as Cell and RefCell. These types allow for mutation of their contents even through an immutable, shared reference. For example the set method on Cell<T> takes &self, so it requires only a shared reference &Cell<T>. The method performs no synchronization, thus Cell cannot be Sync.

Another example of a non-Sync type is the reference-counting pointer Rc. Given any reference &Rc<T>, you can clone a new Rc<T>, modifying the reference counts in a non-atomic way.

For cases when one does need thread-safe interior mutability, Rust provides atomic data types, as well as explicit locking via sync::Mutex and sync::RwLock. These types ensure that any mutation cannot cause data races, hence the types are Sync. Likewise, sync::Arc provides a thread-safe analogue of Rc.

Any types with interior mutability must also use the cell::UnsafeCell wrapper around the value(s) which can be mutated through a shared reference. Failing to doing this is undefined behavior. For example, transmute-ing from &T to &mut T is invalid.

See the Nomicon for more details about Sync.

Implementations on Foreign Types

impl Sync for Argument

impl Sync for FormatSpec

impl Sync for Alignment

impl Sync for Count

impl<'_, T> Sync for RwLockWriteGuard<'_, T> where
    T: Sync + ?Sized, 

impl Sync for Once

impl<'a> Sync for IoSliceMut<'a>

impl<T> Sync for RwLock<T> where
    T: Send + Sync + ?Sized, 

impl<T> Sync for SyncOnceCell<T> where
    T: Send + Sync, 

impl<T> !Sync for Sender<T>

impl<'_, T> Sync for MutexGuard<'_, T> where
    T: Sync + ?Sized, 

impl !Sync for Args

impl<T, F> Sync for SyncLazy<T, F> where
    F: Send,
    SyncOnceCell<T>: Sync, 

impl<'a> Sync for IoSlice<'a>

impl<T> Sync for Mutex<T> where
    T: Send + ?Sized, 

impl<T> Sync for Key<T>

impl !Sync for ArgsOs

impl<'_, T> Sync for RwLockReadGuard<'_, T> where
    T: Sync + ?Sized, 

impl<T> !Sync for Receiver<T>

impl<T> Sync for JoinHandle<T>

impl Sync for Waker

impl Sync for AtomicI16

impl Sync for AtomicI32

impl<T> !Sync for UnsafeCell<T> where
    T: ?Sized, 

impl<'_, T> Sync for Iter<'_, T> where
    T: Sync, 

impl Sync for AtomicBool

impl Sync for AtomicU8

impl Sync for AtomicU32

impl Sync for AtomicI64

impl<T> Sync for Empty<T>

impl<T> Sync for AtomicPtr<T>

impl<T> !Sync for *const T where
    T: ?Sized, 

impl Sync for AtomicUsize

impl<T> !Sync for Cell<T> where
    T: ?Sized, 

impl<'_, T> Sync for IterMut<'_, T> where
    T: Sync, 

impl<T> !Sync for NonNull<T> where
    T: ?Sized, 

NonNull pointers are not Sync because the data they reference may be aliased.

impl<T> !Sync for RefCell<T> where
    T: ?Sized, 

impl Sync for AtomicU64

impl Sync for AtomicIsize

impl<T> !Sync for *mut T where
    T: ?Sized, 

impl Sync for AtomicU16

impl Sync for AtomicI8

impl<'_, T> Sync for CursorMut<'_, T> where
    T: Sync, 

impl<T> Sync for Weak<T> where
    T: Send + Sync + ?Sized, 

impl<T> !Sync for Rc<T> where
    T: ?Sized, 

impl<'_, T> Sync for IterMut<'_, T> where
    T: Sync, 

impl<'_, T> Sync for Iter<'_, T> where
    T: Sync, 

impl<T> !Sync for Weak<T> where
    T: ?Sized, 

impl<'_, T> Sync for IterMut<'_, T> where
    T: Sync, 

impl<'_, T, A> Sync for Drain<'_, T, A> where
    T: Sync,
    A: Sync + Allocator, 

impl<T> Sync for LinkedList<T> where
    T: Sync, 

impl<'_> Sync for Drain<'_>

impl<T, A> Sync for IntoIter<T, A> where
    T: Sync,
    A: Allocator, 

impl<T> Sync for Arc<T> where
    T: Send + Sync + ?Sized, 

impl<'_, T> Sync for Cursor<'_, T> where
    T: Sync, 

impl<'_, T> Sync for Drain<'_, T> where
    T: Sync, 

impl<'a, A> Sync for Drain<'a, A> where
    A: Array + Sync, 

impl<T> Sync for ThreadLocal<T> where
    T: Send, 

impl<T, C> Sync for OwnedRefMut<T, C> where
    C: Config,
    T: Sync + Clear + Default, 

impl<T, C> Sync for Pool<T, C> where
    C: Config,
    T: Sync + Clear + Default, 

impl<T, C> Sync for Slab<T, C> where
    C: Config,
    T: Sync, 

impl<T, C> Sync for OwnedRef<T, C> where
    C: Config,
    T: Sync + Clear + Default, 

impl<T, C> Sync for OwnedEntry<T, C> where
    C: Config,
    T: Sync, 

impl<'a, T> Sync for Drain<'a, T> where
    T: Array + Sync, 

impl<'a, A> Sync for Drain<'a, A> where
    A: Array + Sync, 

impl<T, N> Sync for GenericArray<T, N> where
    T: Sync,
    N: ArrayLength<T>, 

impl<'a, R, T> Sync for RwLockUpgradableReadGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLockUpgrade, 

impl<'a, R, T> Sync for RwLockWriteGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLock, 

impl<'a, R, T> Sync for MappedRwLockWriteGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLock, 

impl<R, T> Sync for RwLock<R, T> where
    T: Send + Sync + ?Sized,
    R: RawRwLock + Sync, 

impl<'a, R, G, T> Sync for MappedReentrantMutexGuard<'a, R, G, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync,
    G: 'a + GetThreadId + Sync, 

impl<'a, R, T> Sync for MutexGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync, 

impl<R, G, T> Sync for ReentrantMutex<R, G, T> where
    T: Send + ?Sized,
    R: RawMutex + Sync,
    G: GetThreadId + Sync, 

impl<'a, R, T> Sync for RwLockReadGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLock, 

impl<R, T> Sync for Mutex<R, T> where
    T: Send + ?Sized,
    R: RawMutex + Sync, 

impl<'a, R, T> Sync for MappedRwLockReadGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLock, 

impl<'a, R, T> Sync for MappedMutexGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync, 

impl<'a, R, G, T> Sync for ReentrantMutexGuard<'a, R, G, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync,
    G: 'a + GetThreadId + Sync, 

impl<T, F, S> Sync for ScopeGuard<T, F, S> where
    T: Sync,
    F: FnOnce(T),
    S: Strategy, 

impl<T, N> Sync for GenericArray<T, N> where
    T: Sync,
    N: ArrayLength<T>, 

impl<T, F> Sync for Lazy<T, F> where
    F: Send,
    OnceCell<T>: Sync, 

impl<'a, R, T> Sync for MappedRwLockReadGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLock, 

impl<'a, R, T> Sync for MutexGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync, 

impl<'a, R, T> Sync for MappedMutexGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync, 

impl<'a, R, G, T> Sync for ReentrantMutexGuard<'a, R, G, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync,
    G: 'a + GetThreadId + Sync, 

impl<'a, R, T> Sync for MappedRwLockWriteGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLock, 

impl<R, T> Sync for Mutex<R, T> where
    T: Send + ?Sized,
    R: RawMutex + Sync, 

impl<R, G> Sync for RawReentrantMutex<R, G> where
    R: RawMutex + Sync,
    G: GetThreadId + Sync, 

impl<R, T> Sync for RwLock<R, T> where
    T: Send + Sync + ?Sized,
    R: RawRwLock + Sync, 

impl Sync for GuardNoSend

impl<'a, R, G, T> Sync for MappedReentrantMutexGuard<'a, R, G, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawMutex + Sync,
    G: 'a + GetThreadId + Sync, 

impl<R, G, T> Sync for ReentrantMutex<R, G, T> where
    T: Send + ?Sized,
    R: RawMutex + Sync,
    G: GetThreadId + Sync, 

impl<'a, R, T> Sync for RwLockUpgradableReadGuard<'a, R, T> where
    T: 'a + Sync + ?Sized,
    R: 'a + RawRwLockUpgrade, 

impl<'_, K, V, S> Sync for OccupiedEntry<'_, K, V, S> where
    K: Sync,
    V: Sync,
    S: Sync, 

impl<'_, K, V> Sync for RawOccupiedEntryMut<'_, K, V> where
    K: Sync,
    V: Sync, 

impl Sync for AtomicWaker

impl<T> Sync for Mutex<T> where
    T: Send + ?Sized, 

impl<'_, T, U> Sync for MappedMutexGuard<'_, T, U> where
    T: Sync + ?Sized,
    U: Sync + ?Sized, 

impl<Fut> Sync for FuturesUnordered<Fut> where
    Fut: Sync, 

impl<'_, T> Sync for MutexLockFuture<'_, T> where
    T: ?Sized, 

impl<'_, T> Sync for MutexGuard<'_, T> where
    T: Sync + ?Sized, 

impl<'_, K, V, S> Sync for OccupiedEntry<'_, K, V, S> where
    K: Sync,
    V: Sync,
    S: Sync, 

impl<'_, K, V, S> Sync for RawOccupiedEntryMut<'_, K, V, S> where
    K: Sync,
    V: Sync,
    S: Sync, 

impl Sync for isize

impl<T> Sync for [T] where
    T: Sync, 

impl Sync for [u8]

impl Sync for char

impl Sync for u128

impl Sync for u16

impl Sync for i128

impl Sync for i16

impl Sync for str

impl Sync for f64

impl Sync for u64

impl Sync for u8

impl Sync for i64

impl Sync for i8

impl<T, const N: usize> Sync for [T; N] where
    T: Sync, 

impl Sync for bool

impl Sync for f32

impl Sync for u32

impl Sync for usize

impl Sync for i32

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Implementors

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Auto implementors

impl Sync for DispatchError

impl Sync for frame_support::dispatch::fmt::Alignment

impl Sync for Never

impl Sync for Void

impl Sync for RuntimeMetadata

impl Sync for StorageEntryModifier

impl Sync for StorageEntryType

impl Sync for StorageHasher

impl Sync for ChildInfo

impl Sync for ChildType

impl Sync for BalanceStatus

impl Sync for ExistenceRequirement

impl Sync for WithdrawReason

impl Sync for DispatchClass

impl Sync for Pays

impl Sync for FrameTransactionPriority

impl Sync for RuntimeLogger

impl Sync for Writer

impl Sync for Error

impl Sync for PhantomPinned

impl Sync for ErrorMetadata

impl Sync for FunctionArgumentMetadata

impl Sync for FunctionMetadata

impl Sync for ModuleConstantMetadata

impl Sync for EventMetadata

impl Sync for OuterEventMetadata

impl Sync for DefaultByteGetter

impl Sync for ExtrinsicMetadata

impl Sync for ModuleMetadata

impl Sync for RuntimeMetadataPrefixed

impl Sync for StorageEntryMetadata

impl Sync for StorageMetadata

impl Sync for Blake2_128

impl Sync for Blake2_128Concat

impl Sync for Blake2_256

impl Sync for Identity

impl Sync for Twox64Concat

impl Sync for Twox128

impl Sync for Twox256

impl Sync for CallMetadata

impl Sync for TestRandomness

impl Sync for WithdrawReasons

impl Sync for BlockExecutionWeight

impl Sync for ExtrinsicBaseWeight

impl Sync for ParityDbWeight

impl Sync for RocksDbWeight

impl Sync for DispatchInfo

impl Sync for PostDispatchInfo

impl Sync for RuntimeDbWeight

impl<'a> !Sync for Arguments<'a>

impl<'a> !Sync for Formatter<'a>

impl<'a, 'b> !Sync for DebugList<'a, 'b>

impl<'a, 'b> !Sync for DebugMap<'a, 'b>

impl<'a, 'b> !Sync for DebugSet<'a, 'b>

impl<'a, 'b> !Sync for DebugStruct<'a, 'b>

impl<'a, 'b> !Sync for DebugTuple<'a, 'b>

impl<'a, T> Sync for frame_support::dispatch::result::Iter<'a, T> where
    T: Sync, 

impl<'a, T> Sync for frame_support::dispatch::result::IterMut<'a, T> where
    T: Sync, 

impl<B, O> Sync for DecodeDifferent<B, O> where
    B: Sync,
    O: Sync, 

impl<B, P> Sync for SignedImbalance<B, P> where
    P: Sync,
    <P as Imbalance<B>>::Opposite: Sync, 

impl<Balance> Sync for WeightToFeeCoefficient<Balance> where
    Balance: Sync, 

impl<Balance, Imbalance, Part1, Target1, Part2, Target2> Sync for SplitTwoWays<Balance, Imbalance, Part1, Target1, Part2, Target2> where
    Balance: Sync,
    Imbalance: Sync,
    Part1: Sync,
    Part2: Sync,
    Target1: Sync,
    Target2: Sync, 

impl<BlockNumber> Sync for DispatchTime<BlockNumber> where
    BlockNumber: Sync, 

impl<E> Sync for FnEncode<E>

impl<F, T> Sync for ClearFilterGuard<F, T> where
    T: Sync,
    <F as FilterStack<T>>::Stack: Sync, 

impl<F, T> Sync for FilterStackGuard<F, T> where
    F: Sync,
    T: Sync, 

impl<K, T, H> Sync for StorageKeyIterator<K, T, H> where
    H: Sync,
    K: Sync,
    T: Sync, 

impl<R> Sync for TransactionOutcome<R> where
    R: Sync, 

impl<S, Created, Removed, K, T> Sync for StorageMapShim<S, Created, Removed, K, T> where
    Created: Sync,
    K: Sync,
    Removed: Sync,
    S: Sync,
    T: Sync, 

impl<T> Sync for frame_support::dispatch::result::IntoIter<T> where
    T: Sync, 

impl<T> Sync for StorageIterator<T> where
    T: Sync, 

impl<T> Sync for PrefixIterator<T>

impl<T> Sync for IdentityFee<T> where
    T: Sync, 

impl<T, A> Sync for Vec<T, A> where
    A: Sync,
    T: Sync, 

impl<T, E> Sync for Result<T, E> where
    E: Sync,
    T: Sync, 

impl<T: ?Sized> Sync for PhantomData<T> where
    T: Sync, 

impl<WD, CD, PF> Sync for FunctionOf<WD, CD, PF> where
    CD: Sync,
    PF: Sync,
    WD: Sync, 

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