Tracking Issue for Mutex::unlock()

[mark-i-m]

Feature gate: #![feature(mutex_unlock)]

This is a tracking issue for the Mutex::unlock function. The goal of this function is to replace drop(mutex_guard) which doesn't clear express that a synchronization event is occurring.

Some earlier discussion, including a previous implementation: #79434 (comment)

Public API

// std::sync::Mutex

impl<T> Mutex<T> {
    /// Immediately drops the guard, unlocking the mutex.
    ///
    /// This is equivalent to `drop(guard)`, but it is more self-documenting.
    pub fn unlock(guard: MutexGuard<T>) {
        drop(guard);
    }
}

Steps / History

• Implementation: Add Mutex::unlock #81873
• Final commenting period (FCP)
• Stabilization PR

Unresolved Questions

• Should an analogous function be added to RwLock? It would be a bit more complicated.

[mbrubeck]

I don't think this needs to require T: Sized. Should it be moved to impl<T: ?Sized> Mutex<T>?

[mark-i-m]

I can make a PR for that...

[ibraheemdev]

A bit pedantic, but wouldn't it make sense for the drop impl for MutexGuard to call unlock, and the logic to be moved there?

[mbrubeck]

A bit pedantic, but wouldn't it make sense for the drop impl for MutexGuard to call unlock, and the logic to be moved there?

MutexGuard::drop takes &mut self, so it can't easily call unlock, which consumes the MutexGuard by value.

[ibraheemdev]

Ah right, that is problematic.

[frogtd]

The drop function call is useless BTW, but it could make it slightly more clear.

[StrongerXi]

Any progress on this? Wondering why it's still pending...