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author | Sean McArthur <sean@seanmonstar.com> | 2020-09-23 13:02:15 -0700 |
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committer | GitHub <noreply@github.com> | 2020-09-23 13:02:15 -0700 |
commit | a0557840eb424e174bf81a0175c40f9e176a2cc2 (patch) | |
tree | 676d33bf4144f0c0aac5af9f826ecc216a1d50e2 /tokio/src/sync | |
parent | f25f12d57638a2928b3f738b3b1392d8773e276e (diff) |
io: use intrusive wait list for I/O driver (#2828)
This refactors I/O registration in a few ways:
- Cleans up the cached readiness in `PollEvented`. This cache used to
be helpful when readiness was a linked list of `*mut Node`s in
`Registration`. Previous refactors have turned `Registration` into just
an `AtomicUsize` holding the current readiness, so the cache is just
extra work and complexity. Gone.
- Polling the `Registration` for readiness now gives a `ReadyEvent`,
which includes the driver tick. This event must be passed back into
`clear_readiness`, so that the readiness is only cleared from `Registration`
if the tick hasn't changed. Previously, it was possible to clear the
readiness even though another thread had *just* polled the driver and
found the socket ready again.
- Registration now also contains an `async fn readiness`, which stores
wakers in an instrusive linked list. This allows an unbounded number
of tasks to register for readiness (previously, only 1 per direction (read
and write)). By using the intrusive linked list, there is no concern of
leaking the storage of the wakers, since they are stored inside the `async fn`
and released when the future is dropped.
- Registration retains a `poll_readiness(Direction)` method, to support
`AsyncRead` and `AsyncWrite`. They aren't able to use `async fn`s, and
so there are 2 reserved slots for those methods.
- IO types where it makes sense to have multiple tasks waiting on them
now take advantage of this new `async fn readiness`, such as `UdpSocket`
and `UnixDatagram`.
Additionally, this makes the `io-driver` "feature" internal-only (no longer
documented, not part of public API), and adds a second internal-only
feature, `io-readiness`, to group together linked list part of registration
that is only used by some of the IO types.
After a bit of discussion, changing stream-based transports (like
`TcpStream`) to have `async fn read(&self)` is punted, since that
is likely too easy of a footgun to activate.
Refs: #2779, #2728
Diffstat (limited to 'tokio/src/sync')
-rw-r--r-- | tokio/src/sync/task/atomic_waker.rs | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/tokio/src/sync/task/atomic_waker.rs b/tokio/src/sync/task/atomic_waker.rs index 73b1745f..ae4cac7c 100644 --- a/tokio/src/sync/task/atomic_waker.rs +++ b/tokio/src/sync/task/atomic_waker.rs @@ -141,13 +141,12 @@ impl AtomicWaker { } } + /* /// Registers the current waker to be notified on calls to `wake`. - /// - /// This is the same as calling `register_task` with `task::current()`. - #[cfg(feature = "io-driver")] pub(crate) fn register(&self, waker: Waker) { self.do_register(waker); } + */ /// Registers the provided waker to be notified on calls to `wake`. /// |