pub unsafe auto trait Sync { }Expand description
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.
A shorter overview of how Sync and Send relate to referencing:
&TisSendif and only ifTisSync&mut TisSendif and only ifTisSend&Tand&mut TareSyncif and only ifTisSync
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.
Implementors§
impl !Sync for LocalWaker
impl !Sync for Arguments<'_>
impl !Sync for Args
impl !Sync for ArgsOs
impl Sync for avail_rust_client::ext::subxt_signer::bip39::core::ffi::c_str::Bytes<'_>
impl Sync for avail_rust_client::ext::subxt_signer::bip39::core::panic::Location<'_>
impl Sync for Waker
impl Sync for TypeId
impl Sync for alloc::string::Drain<'_>
impl Sync for AtomicBool
impl Sync for AtomicI8
impl Sync for AtomicI16
impl Sync for AtomicI32
impl Sync for AtomicI64
impl Sync for AtomicIsize
impl Sync for AtomicU8
impl Sync for AtomicU16
impl Sync for AtomicU32
impl Sync for AtomicU64
impl Sync for AtomicUsize
impl Sync for atomic_waker::AtomicWaker
impl Sync for bytes::bytes::Bytes
impl Sync for BytesMut
impl Sync for futures_core::task::__internal::atomic_waker::AtomicWaker
impl Sync for Asn1BitString
impl Sync for Asn1BitStringRef
impl Sync for Asn1Enumerated
impl Sync for Asn1EnumeratedRef
impl Sync for Asn1GeneralizedTime
impl Sync for Asn1GeneralizedTimeRef
impl Sync for Asn1Integer
impl Sync for Asn1IntegerRef
impl Sync for Asn1Object
impl Sync for Asn1ObjectRef
impl Sync for Asn1OctetString
impl Sync for Asn1OctetStringRef
impl Sync for Asn1String
impl Sync for Asn1StringRef
impl Sync for Asn1Time
impl Sync for Asn1TimeRef
impl Sync for BigNum
impl Sync for BigNumContext
impl Sync for BigNumContextRef
impl Sync for BigNumRef
impl Sync for openssl::cipher::Cipher
impl Sync for CipherRef
impl Sync for CipherCtx
impl Sync for CipherCtxRef
impl Sync for CmsContentInfo
impl Sync for CmsContentInfoRef
impl Sync for Conf
impl Sync for ConfRef
impl Sync for Deriver<'_>
impl Sync for DsaSig
impl Sync for DsaSigRef
impl Sync for EcGroup
impl Sync for EcGroupRef
impl Sync for EcPoint
impl Sync for EcPointRef
impl Sync for EcdsaSig
impl Sync for EcdsaSigRef
impl Sync for Decrypter<'_>
impl Sync for Encrypter<'_>
impl Sync for openssl::error::Error
impl Sync for Hasher
impl Sync for MessageDigest
impl Sync for LibCtx
impl Sync for LibCtxRef
impl Sync for Md
impl Sync for MdRef
impl Sync for MdCtx
impl Sync for MdCtxRef
impl Sync for OcspBasicResponse
impl Sync for OcspBasicResponseRef
impl Sync for OcspCertId
impl Sync for OcspCertIdRef
impl Sync for OcspOneReq
impl Sync for OcspOneReqRef
impl Sync for OcspRequest
impl Sync for OcspRequestRef
impl Sync for OcspResponse
impl Sync for OcspResponseRef
impl Sync for Pkcs7
impl Sync for Pkcs7Ref
impl Sync for Pkcs7Signed
impl Sync for Pkcs7SignedRef
impl Sync for Pkcs7SignerInfo
impl Sync for Pkcs7SignerInfoRef
impl Sync for Pkcs12
impl Sync for Pkcs12Ref
impl Sync for Provider
impl Sync for ProviderRef
impl Sync for Signer<'_>
impl Sync for Verifier<'_>
impl Sync for SrtpProtectionProfile
impl Sync for SrtpProtectionProfileRef
impl Sync for Ssl
impl Sync for SslContext
impl Sync for SslContextRef
impl Sync for SslMethod
impl Sync for SslRef
impl Sync for SslSession
impl Sync for SslSessionRef
impl Sync for OpensslString
impl Sync for OpensslStringRef
impl Sync for openssl::symm::Cipher
impl Sync for X509Store
impl Sync for X509StoreBuilder
impl Sync for X509StoreBuilderRef
impl Sync for X509StoreRef
impl Sync for AccessDescription
impl Sync for AccessDescriptionRef
impl Sync for DistPoint
impl Sync for DistPointName
impl Sync for DistPointNameRef
impl Sync for DistPointRef
impl Sync for GeneralName
impl Sync for GeneralNameRef
impl Sync for X509
impl Sync for X509Algorithm
impl Sync for X509AlgorithmRef
impl Sync for X509Crl
impl Sync for X509CrlRef
impl Sync for X509Extension
impl Sync for X509ExtensionRef
impl Sync for X509Name
impl Sync for X509NameEntry
impl Sync for X509NameEntryRef
impl Sync for X509NameRef
impl Sync for X509Object
impl Sync for X509ObjectRef
impl Sync for X509Ref
impl Sync for X509Req
impl Sync for X509ReqRef
impl Sync for X509Revoked
impl Sync for X509RevokedRef
impl Sync for X509StoreContext
impl Sync for X509StoreContextRef
impl Sync for X509VerifyParam
impl Sync for X509VerifyParamRef
impl Sync for AbortHandle
impl Sync for OwnedNotified
impl<'a> Sync for IoSlice<'a>
impl<'a> Sync for IoSliceMut<'a>
impl<'a> Sync for Notified<'a>
impl<'a, 'b, K, Q, V, S, A> Sync for OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
impl<'a, T> Sync for http::header::map::Drain<'a, T>where
T: Sync,
impl<'a, T> Sync for http::header::map::Iter<'a, T>where
T: Sync,
impl<'a, T> Sync for http::header::map::IterMut<'a, T>where
T: Sync,
impl<'a, T> Sync for ValueDrain<'a, T>where
T: Sync,
impl<'a, T> Sync for ValueIterMut<'a, T>where
T: Sync,
impl<'a, T> Sync for OnceRef<'a, T>where
T: Sync,
impl<'a, T> Sync for smallvec::Drain<'a, T>
impl<'a, T> Sync for tokio::sync::mutex::MappedMutexGuard<'a, T>
impl<'a, T> Sync for ZeroVec<'a, T>
impl<'a, T, const CAP: usize> Sync for arrayvec::arrayvec::Drain<'a, T, CAP>where
T: Sync,
impl<C> Sync for CartableOptionPointer<C>where
C: Send + CartablePointerLike,
impl<Dyn> Sync for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<Fut> Sync for futures_util::stream::futures_unordered::iter::IntoIter<Fut>
impl<Fut> Sync for IterPinMut<'_, Fut>where
Fut: Sync,
impl<Fut> Sync for IterPinRef<'_, Fut>where
Fut: Sync,
impl<Fut> Sync for FuturesUnordered<Fut>
impl<K, V, S, A> Sync for hashbrown::map::OccupiedEntry<'_, K, V, S, A>
impl<K, V, S, A> Sync for RawOccupiedEntryMut<'_, K, V, S, A>
impl<M, T, O> Sync for BitRef<'_, M, T, O>
impl<S> Sync for AllowStd<S>where
S: Sync,
impl<T> !Sync for *const Twhere
T: ?Sized,
impl<T> !Sync for *mut Twhere
T: ?Sized,
impl<T> !Sync for Cell<T>where
T: ?Sized,
impl<T> !Sync for avail_rust_client::ext::subxt_signer::bip39::core::cell::OnceCell<T>
impl<T> !Sync for RefCell<T>where
T: ?Sized,
impl<T> !Sync for UnsafeCell<T>where
T: ?Sized,
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 std::sync::mpsc::Receiver<T>
impl<T> Sync for BitSpanError<T>where
T: BitStore,
impl<T> Sync for ChunksExactMut<'_, T>where
T: Sync,
impl<T> Sync for ChunksMut<'_, T>where
T: Sync,
impl<T> Sync for avail_rust_client::ext::subxt_core::alloc::slice::Iter<'_, T>where
T: Sync,
impl<T> Sync for avail_rust_client::ext::subxt_core::alloc::slice::IterMut<'_, T>where
T: Sync,
impl<T> Sync for RChunksExactMut<'_, T>where
T: Sync,
impl<T> Sync for RChunksMut<'_, T>where
T: Sync,
impl<T> Sync for SyncUnsafeCell<T>
impl<T> Sync for UnsafePinned<T>
impl<T> Sync for Exclusive<T>where
T: ?Sized,
impl<T> Sync for NonZero<T>where
T: ZeroablePrimitive + Sync,
impl<T> Sync for ThinBox<T>
ThinBox<T> is Sync if T is Sync because the data is owned.
impl<T> Sync for alloc::collections::linked_list::Iter<'_, T>where
T: Sync,
impl<T> Sync for alloc::collections::linked_list::IterMut<'_, T>where
T: Sync,
impl<T> Sync for AtomicPtr<T>
impl<T> Sync for std::sync::mpmc::Receiver<T>where
T: Send,
impl<T> Sync for std::sync::mpmc::Sender<T>where
T: Send,
impl<T> Sync for std::sync::mpsc::Sender<T>where
T: Send,
impl<T> Sync for std::sync::nonpoison::mutex::MappedMutexGuard<'_, T>
impl<T> Sync for std::sync::nonpoison::mutex::Mutex<T>
T must be Send for Mutex to be Sync.
This ensures that the protected data can be accessed safely from multiple threads
without causing data races or other unsafe behavior.
Mutex<T> provides mutable access to T to one thread at a time. However, it’s essential
for T to be Send because it’s not safe for non-Send structures to be accessed in
this manner. For instance, consider Rc, a non-atomic reference counted smart pointer,
which is not Send. With Rc, we can have multiple copies pointing to the same heap
allocation with a non-atomic reference count. If we were to use Mutex<Rc<_>>, it would
only protect one instance of Rc from shared access, leaving other copies vulnerable
to potential data races.
Also note that it is not necessary for T to be Sync as &T is only made available
to one thread at a time if T is not Sync.
impl<T> Sync for std::sync::nonpoison::mutex::MutexGuard<'_, T>
T must be Sync for a MutexGuard<T> to be Sync
because it is possible to get a &T from &MutexGuard (via Deref).
impl<T> Sync for std::sync::nonpoison::rwlock::MappedRwLockReadGuard<'_, T>
impl<T> Sync for std::sync::nonpoison::rwlock::MappedRwLockWriteGuard<'_, T>
impl<T> Sync for std::sync::nonpoison::rwlock::RwLock<T>
impl<T> Sync for std::sync::nonpoison::rwlock::RwLockReadGuard<'_, T>
impl<T> Sync for std::sync::nonpoison::rwlock::RwLockWriteGuard<'_, T>
impl<T> Sync for OnceLock<T>
impl<T> Sync for std::sync::poison::mutex::MappedMutexGuard<'_, T>
impl<T> Sync for std::sync::poison::mutex::Mutex<T>
T must be Send for Mutex to be Sync.
This ensures that the protected data can be accessed safely from multiple threads
without causing data races or other unsafe behavior.
Mutex<T> provides mutable access to T to one thread at a time. However, it’s essential
for T to be Send because it’s not safe for non-Send structures to be accessed in
this manner. For instance, consider Rc, a non-atomic reference counted smart pointer,
which is not Send. With Rc, we can have multiple copies pointing to the same heap
allocation with a non-atomic reference count. If we were to use Mutex<Rc<_>>, it would
only protect one instance of Rc from shared access, leaving other copies vulnerable
to potential data races.
Also note that it is not necessary for T to be Sync as &T is only made available
to one thread at a time if T is not Sync.
impl<T> Sync for std::sync::poison::mutex::MutexGuard<'_, T>
T must be Sync for a MutexGuard<T> to be Sync
because it is possible to get a &T from &MutexGuard (via Deref).
impl<T> Sync for std::sync::poison::rwlock::MappedRwLockReadGuard<'_, T>
impl<T> Sync for std::sync::poison::rwlock::MappedRwLockWriteGuard<'_, T>
impl<T> Sync for std::sync::poison::rwlock::RwLock<T>
impl<T> Sync for std::sync::poison::rwlock::RwLockReadGuard<'_, T>
impl<T> Sync for std::sync::poison::rwlock::RwLockWriteGuard<'_, T>
impl<T> Sync for ReentrantLock<T>
impl<T> Sync for ReentrantLockGuard<'_, T>
impl<T> Sync for std::thread::JoinHandle<T>
impl<T> Sync for MisalignError<T>
impl<T> Sync for futures_util::lock::mutex::Mutex<T>
impl<T> Sync for futures_util::lock::mutex::MutexGuard<'_, T>
impl<T> Sync for MutexLockFuture<'_, T>where
T: ?Sized,
impl<T> Sync for futures_util::lock::mutex::OwnedMutexGuard<T>
impl<T> Sync for OwnedMutexLockFuture<T>where
T: ?Sized,
impl<T> Sync for OnceBox<T>
impl<T> Sync for Dh<T>
impl<T> Sync for DhRef<T>
impl<T> Sync for Dsa<T>
impl<T> Sync for DsaRef<T>
impl<T> Sync for EcKey<T>
impl<T> Sync for EcKeyRef<T>
impl<T> Sync for PKey<T>
impl<T> Sync for PKeyRef<T>
impl<T> Sync for PkeyCtx<T>
impl<T> Sync for PkeyCtxRef<T>
impl<T> Sync for Rsa<T>
impl<T> Sync for RsaRef<T>
impl<T> Sync for Stack<T>
impl<T> Sync for StackRef<T>
impl<T> Sync for X509Lookup<T>
impl<T> Sync for X509LookupMethod<T>
impl<T> Sync for X509LookupMethodRef<T>
impl<T> Sync for X509LookupRef<T>
impl<T> Sync for SyncWrapper<T>
impl<T> Sync for ThreadLocal<T>where
T: Send,
impl<T> Sync for ReadHalf<T>where
T: Sync,
impl<T> Sync for WriteHalf<T>where
T: Sync,
impl<T> Sync for tokio::runtime::task::join::JoinHandle<T>where
T: Send,
impl<T> Sync for tokio::sync::mutex::Mutex<T>
impl<T> Sync for tokio::sync::mutex::MutexGuard<'_, T>
impl<T> Sync for tokio::sync::mutex::OwnedMutexGuard<T>
impl<T> Sync for tokio::sync::once_cell::OnceCell<T>
impl<T> Sync for OwnedRwLockWriteGuard<T>
impl<T> Sync for tokio::sync::rwlock::read_guard::RwLockReadGuard<'_, T>
impl<T> Sync for tokio::sync::rwlock::RwLock<T>
impl<T> Sync for tokio::sync::rwlock::write_guard::RwLockWriteGuard<'_, T>
impl<T> Sync for RwLockMappedWriteGuard<'_, T>
impl<T> Sync for SetOnce<T>
impl<T> Sync for TryLock<T>where
T: Send,
impl<T, A> !Sync for Rc<T, A>
impl<T, A> !Sync for UniqueRc<T, A>
impl<T, A> !Sync for alloc::rc::Weak<T, A>
impl<T, A> Sync for LinkedList<T, A>
impl<T, A> Sync for Arc<T, A>
impl<T, A> Sync for UniqueArc<T, A>
impl<T, A> Sync for avail_rust_client::ext::subxt_core::alloc::sync::Weak<T, A>
impl<T, A> Sync for alloc::collections::linked_list::Cursor<'_, T, A>
impl<T, A> Sync for alloc::collections::linked_list::CursorMut<'_, T, A>
impl<T, A> Sync for alloc::collections::vec_deque::drain::Drain<'_, T, A>
impl<T, A> Sync for alloc::vec::drain::Drain<'_, T, A>
impl<T, A> Sync for alloc::vec::into_iter::IntoIter<T, A>
impl<T, A> Sync for allocator_api2::stable::boxed::Box<T, A>
impl<T, A> Sync for allocator_api2::stable::vec::drain::Drain<'_, T, A>
impl<T, A> Sync for allocator_api2::stable::vec::into_iter::IntoIter<T, A>
impl<T, A> Sync for hashbrown::table::OccupiedEntry<'_, T, A>
impl<T, C> Sync for OwnedRef<T, C>
impl<T, C> Sync for OwnedRefMut<T, C>
impl<T, C> Sync for Pool<T, C>
impl<T, C> Sync for OwnedEntry<T, C>
impl<T, C> Sync for Slab<T, C>
impl<T, F> Sync for LazyLock<T, F>
impl<T, F> Sync for Lazy<T, F>
impl<T, N> Sync for GenericArray<T, N>where
T: Sync,
N: ArrayLength<T>,
impl<T, O> Sync for bitvec::boxed::iter::IntoIter<T, O>
impl<T, O> Sync for BitBox<T, O>
impl<T, O> Sync for bitvec::slice::iter::Iter<'_, T, O>
impl<T, O> Sync for bitvec::slice::iter::IterMut<'_, T, O>
impl<T, O> Sync for BitSlice<T, O>
§Bit-Slice Thread Safety
This allows bit-slice references to be moved across thread boundaries only when
the underlying T element can tolerate concurrency.
All BitSlice references, shared or exclusive, are only threadsafe if the T
element type is Send, because any given bit-slice reference may only have
partial control of a memory element that is also being shared by a bit-slice
reference on another thread. As such, this is never implemented for Cell<U>,
but always implemented for AtomicU and U for a given unsigned integer type
U.
Atomic integers safely handle concurrent writes, cells do not allow concurrency
at all, so the only missing piece is &mut BitSlice<_, U: Unsigned>. This is
handled by the aliasing system that the mutable splitters employ: a mutable
reference to an unsynchronized bit-slice can only cross threads when no other
handle is able to exist to the elements it governs. Splitting a mutable
bit-slice causes the split halves to change over to either atomics or cells, so
concurrency is either safe or impossible.