Struct kernel::revocable::Revocable

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pub struct Revocable<T> { /* private fields */ }

Expand description

An object that can become inaccessible at runtime.

Once access is revoked and all concurrent users complete (i.e., all existing instances of RevocableGuard are dropped), the wrapped object is also dropped.

Examples


struct Example {
    a: u32,
    b: u32,
}

fn add_two(v: &Revocable<Example>) -> Option<u32> {
    let guard = v.try_access()?;
    Some(guard.a + guard.b)
}

let v = Revocable::new(Example { a: 10, b: 20 });
assert_eq!(add_two(&v), Some(30));
v.revoke();
assert_eq!(add_two(&v), None);

Sample example as above, but explicitly using the rcu read side lock.

use kernel::sync::rcu;

struct Example {
    a: u32,
    b: u32,
}

fn add_two(v: &Revocable<Example>) -> Option<u32> {
    let guard = rcu::read_lock();
    let e = v.try_access_with_guard(&guard)?;
    Some(e.a + e.b)
}

let v = Revocable::new(Example { a: 10, b: 20 });
assert_eq!(add_two(&v), Some(30));
v.revoke();
assert_eq!(add_two(&v), None);

Implementations

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impl<T> Revocable<T>

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pub const fn new(data: T) -> Self

Creates a new revocable instance of the given data.

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pub fn try_access(&self) -> Option<RevocableGuard<'_, T>>

Tries to access the [revocable] wrapped object.

Returns None if the object has been revoked and is therefore no longer accessible.

Returns a guard that gives access to the object otherwise; the object is guaranteed to remain accessible while the guard is alive. In such cases, callers are not allowed to sleep because another CPU may be waiting to complete the revocation of this object.

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pub fn try_access_with_guard<'a>(&'a self, _guard: &'a Guard) -> Option<&'a T>

Tries to access the [revocable] wrapped object.

Returns None if the object has been revoked and is therefore no longer accessible.

Returns a shared reference to the object otherwise; the object is guaranteed to remain accessible while the rcu read side guard is alive. In such cases, callers are not allowed to sleep because another CPU may be waiting to complete the revocation of this object.

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pub fn revoke(&self)

Revokes access to and drops the wrapped object.

Access to the object is revoked immediately to new callers of Revocable::try_access. If there are concurrent users of the object (i.e., ones that called Revocable::try_access beforehand and still haven’t dropped the returned guard), this function waits for the concurrent access to complete before dropping the wrapped object.