Explicit unlock for locks

What it does

Force locks to have a dedicated block which lock is acquired at first line of it, or an explicit drop.

Categories

• Kind: Restriction

Why?

Implicit drops can be surprising and some users of linux community forum lwn have some concerns about it that can cause bug in linux kernel. It can also encourage people to free locks sooner.

Drawbacks

None.

Example

fn sample(l: Locked) -> i32 {
    let mut x = 2;
    let guard = l.lock();
    x += 3;
    guard.do_sth();
    some_other_work_with_lock();
    x += 4;
    x
}

Could be written as:

fn sample(l: Locked) -> i32 {
    let mut x = 2;
    { // lock block
        let guard = l.lock();
        x += 3;
        guard.do_sth();
        some_other_work_with_lock();
    }
    x += 4;
    x
}

Or with drop:

fn sample(l: Locked) -> i32 {
    let mut x = 2;
    let guard = l.lock();
    x += 3;
    guard.do_sth();
    some_other_work_with_lock();
    drop(guard);
    x += 4;
    x
}

The issue contains only Rust examples and does not name implementation files or tests. Start by reviewing Clippy's existing restriction-lint conventions, then determine how the proposed lock block and explicit drop forms should be specified and tested. Done means the behavior is agreed, implemented, and covered by tests for the examples.