Both `&` and `&mut` can be moved to another thread (through
only `&` can be used by multiple threads). This holds even
if the livetime is not `'static`, but requires the usage of
a scoped threads API which use a trick to assure that the sub-thread(s)
can not outlive the parent thread from which the `&`/`&mut` comes.
Originally such an API was in rust/std but it was removed as it was found to not be sound in the way it was implemented, but sound versions of this API do exist(1) since a long time as libraries and there have been efforts to move it back into std (but I don't know the state of it).
Both `&` and `&mut` can be moved to another thread (through only `&` can be used by multiple threads). This holds even if the livetime is not `'static`, but requires the usage of a scoped threads API which use a trick to assure that the sub-thread(s) can not outlive the parent thread from which the `&`/`&mut` comes.
Originally such an API was in rust/std but it was removed as it was found to not be sound in the way it was implemented, but sound versions of this API do exist(1) since a long time as libraries and there have been efforts to move it back into std (but I don't know the state of it).
(1): For example crossbeam::scope : https://docs.rs/crossbeam/latest/crossbeam/fn.scope.html