Struct Revocable

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

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

Implementations

impl<T> Revocable<T>

pub fn new(data: impl PinInit<T>) -> impl PinInit<Self>

Creates a new revocable instance of the given data.

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Returns None if the object has been revoked and is therefore no longer accessible.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

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Returns None if the object has been revoked and is therefore no longer accessible.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

pub unsafe fn revoke_nosync(&self)

Revokes access to and drops the wrapped object.

Access to the object is revoked immediately to new callers of Revocable::try_access, expecting that there are no concurrent users of the object.

Safety

Callers must ensure that there are no more concurrent users of the revocable object.

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.

Trait Implementations

impl<T> Drop for Revocable<T>

fn drop(&mut self)

Executes the destructor for this type.

impl<T> PinnedDrop for Revocable<T>

fn drop(self: Pin<&mut Self>, _: OnlyCallFromDrop)

Executes the pinned destructor of this type.

impl<T: Send> Send for Revocable<T>

impl<T: Sync + Send> Sync for Revocable<T>