Messages in this thread | | | Date | Tue, 23 May 2023 19:08:50 +0200 | Subject | Re: [PATCH v2 2/4] rust: sync: reword the `Arc` safety comment for `Sync` | From | Alice Ryhl <> |
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On 5/23/23 17:50, Gary Guo wrote: >> -// SAFETY: It is safe to send `&Arc<T>` to another thread when the underlying `T` is `Sync` for the >> -// same reason as above. `T` needs to be `Send` as well because a thread can clone an `&Arc<T>` >> -// into an `Arc<T>`, which may lead to `T` being accessed by the same reasoning as above. >> +// SAFETY: It is safe to send `&Arc<T>` to another thread when the underlying `T` is `Sync` >> +// because it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, >> +// it needs `T` to be `Send` because any thread that has a `&Arc<T>` may clone it and get an >> +// `Arc<T>` on that thread, so the thread may ultimately access `T` using a mutable reference, for >> +// example, when the reference count reaches zero and `T` is dropped. > > "for example" here implies that there are other case to get a mutable > reference? I don't think that's true for our `Arc` since we don't > provide a `get_mut` method.
Ah, yes, that's true. Good point.
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