On Mon Jul 7, 2025 at 3:29 PM CEST, Andreas Hindborg wrote: > Introduce the `SetOnce` type, a container that can only be written once. > The container uses an internal atomic to synchronize writes to the internal > value. > > Signed-off-by: Andreas Hindborg <[email protected]>
One nit and a safety comment fix below. (feel free to ignore the nit) With the safety comment fixed: Reviewed-by: Benno Lossin <[email protected]> > --- > rust/kernel/sync.rs | 2 + > rust/kernel/sync/set_once.rs | 125 > +++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 127 insertions(+) > > diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs > index 81e3a806e57e2..13e6bc7fa87ac 100644 > --- a/rust/kernel/sync.rs > +++ b/rust/kernel/sync.rs > @@ -18,6 +18,7 @@ > mod locked_by; > pub mod poll; > pub mod rcu; > +mod set_once; I would have named this `once`. > pub use arc::{Arc, ArcBorrow, UniqueArc}; > pub use completion::Completion; > + /// Get a reference to the contained object. > + /// > + /// Returns [`None`] if this [`SetOnce`] is empty. > + pub fn as_ref(&self) -> Option<&T> { > + if self.init.load(Acquire) == 2 { > + // SAFETY: By the type invariants of `Self`, `self.init == 2` > means that `self.value` > + // contains a valid value. And the type invariants also ensure that the value of `self.init` doesn't change. So probably // SAFETY: By the type invariants of `Self`, `self.init == 2` means that `self.value` // contains a valid value. They also guarantee that `self.init` doesn't change. If you come up with something better, feel free to use it. --- Cheers, Benno > + Some(unsafe { &*self.value.get() }) > + } else { > + None > + } > + }
