feat(maitake): add wait::Semaphore
#301
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This is a draft primarily because I'd like to add docs. |
wait::Semaphorewait::Semaphore
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@jamesmunns any opinions as to whether this belongs in |
This was referenced Aug 30, 2022
hawkw
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currently, `maitake` has a `wait` module, which contains `WaitCell`, `WaitQueue`, `WaitMap`, and (as of #301) `Semaphore`. in addition, it has a separate `sync` module, which currently contains `Mutex` and nothing else (and may grow a `RwLock` eventually/soon). this feels a bit unfortunate --- the `wait` types are also synchronization primitives. this branch moves all of `maitake::wait` into `maitake::sync`. in addition,i fixed up the docs a little bit. closes #302
hawkw
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This branch adds an async read-write lock implementation in `maitake::sync`. This lock is implemented using the `Semaphore` type added in #301. The rwlock is modeled using a `Semaphore` with `Semaphore::MAX_PERMITS` permits in it; a reader must acquire a single permit to gain read access, while a writer must acquire all the permits.
hawkw
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This branch adds an async read-write lock implementation in `maitake::sync`. This lock is implemented using the `Semaphore` type added in #301. The rwlock is modeled using a `Semaphore` with `Semaphore::MAX_PERMITS` permits in it; a reader must acquire a single permit to gain read access, while a writer must acquire all the permits.
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A semaphore is a useful synchronization type for things like
rate-limiting async tasks. It could also be used as a lower-level
primitive to implement things like read-write locks1 and
channels2.
This branch adds an asynchronous semaphore implementation in
maitake::wait. The implementation is based on the implementation Iwrote for Tokio in tokio-rs/tokio#2325, with some code simplified a bit
as it was not necessary to maintain Tokio's required API surface.
Closes #299
Footnotes
a rwlock can be modeled by a semaphore with n permits (where n
is the maximum number of concurrent readers); each reader must
acquire a single permit, while a writer must acquire n permits). ↩
a bounded MPSC channel of capacity n can be implemented using a
semaphore with n permits, where each producer must acquire a
single permit to write, and every time a message is consumed, the
reader releases a permit to the writers. ↩