Tracking Issue for `rwlock_try_upgrade`

[ShrigmaDev]

Feature gate: #![feature(rwlock_try_upgrade)]

This is a tracking issue RwLock::try_upgrade, which turns a read guard into a write guard if it is the only lock accessor.

Public API

// src/sync/rwlock.rs
impl<'a, T: ?Sized> RwLockReadGuard<'a, T> {
    pub fn try_upgrade(orig: Self) -> Result<RwLockWriteGuard<'a, T>, RwLockReadGuard<'a, T>>;
}

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: Add Rwlock try_upgrade method libs-team#514
• Partial implementation Rwlock try upgrade #138560
• Clippy lint to avoid calling try_upgrade in a loop (not blocking)
• Miri tie-in (not blocking)
• Implementation: #...
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

[tgross35]

The original author hasn't had a chance to work on this, so it is open if anybody wants to pick it up. Labeled hard because the queue implementation is pretty tricky.

Cc @connortsui20 in case you're interested in working on this since you handled downgrade.

[connortsui20]

The original author hasn't had a chance to work on this, so it is open if anybody wants to pick it up. Labeled hard because the queue implementation is pretty tricky.

Cc @connortsui20 in case you're interested in working on this since you handled downgrade.

I can pick this up (but only after next week because I need to graduate). I have a good idea of what needs to be done given the discussion in rust-lang/libs-team#514, but I will point out that I have no idea how to add rust-lang/libs-team#514 (comment) nor how to support a clippy lint that tells people not to put try_upgrade in a loop.

[tgross35]

but only after next week because I need to graduate

Certainly no rush, congrats! 🎉

Don't worry about Clippy, that wouldn't block anything here. Miri likely wouldn't either but it might not be that bad, @RalfJung may have some ideas about what to do here (rust-lang/libs-team#514 (comment) for context Ralf).

[connortsui20]

Also see: rust-lang/libs-team#514 (comment)