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Rollup merge of #45682 - RalfJung:rwlock-guards, r=alexcrichton

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RwLock guards are Sync if T is

Currently, the compiler requires `T` to also be `Send`.  There is no reason for
that.  `&Rw{Read,Write}LockGuard` only provides a shared referenced to `T`, sending
that across threads is safe if `T` is `Sync`.

Cc @oconnor663
This commit is contained in:
kennytm 2017-11-07 15:52:10 +08:00
commit eae36714df
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1 changed files with 8 additions and 3 deletions
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11
src/libstd/sync/rwlock.rs
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@ -10,7 +10,6 @@
use cell::UnsafeCell; use cell::UnsafeCell;
use fmt; use fmt;
use marker;
use mem; use mem;
use ops::{Deref, DerefMut}; use ops::{Deref, DerefMut};
use ptr; use ptr;
@ -102,7 +101,10 @@ pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
} }
#[stable(feature = "rust1", since = "1.0.0")] #[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> !marker::Send for RwLockReadGuard<'a, T> {} impl<'a, T: ?Sized> !Send for RwLockReadGuard<'a, T> {}
#[stable(feature = "rwlock_guard_sync", since = "1.23.0")]
unsafe impl<'a, T: ?Sized + Sync> Sync for RwLockReadGuard<'a, T> {}
/// RAII structure used to release the exclusive write access of a lock when /// RAII structure used to release the exclusive write access of a lock when
/// dropped. /// dropped.
@ -121,7 +123,10 @@ pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
} }
#[stable(feature = "rust1", since = "1.0.0")] #[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> !marker::Send for RwLockWriteGuard<'a, T> {} impl<'a, T: ?Sized> !Send for RwLockWriteGuard<'a, T> {}
#[stable(feature = "rwlock_guard_sync", since = "1.23.0")]
unsafe impl<'a, T: ?Sized + Sync> Sync for RwLockWriteGuard<'a, T> {}
impl<T> RwLock<T> { impl<T> RwLock<T> {
/// Creates a new instance of an `RwLock<T>` which is unlocked. /// Creates a new instance of an `RwLock<T>` which is unlocked.