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Make Pollee semi-stateless

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This commit is contained in:
Ruihan Li
2024-11-17 17:43:34 +08:00
committed by Tate, Hongliang Tian
parent 1c1da8ea06
commit ec2c6ab7a3
11 changed files with 282 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/src/device/pty/pty.rs
View File

@ -102,7 +102,10 @@ impl PtyMaster {
return_errno_with_message!(Errno::EAGAIN, "the buffer is empty");
}
input.read_fallible(writer)
let read_len = input.read_fallible(writer)?;
self.pollee.invalidate();
Ok(read_len)
}
fn check_io_events(&self) -> IoEvents {

2
kernel/src/device/tty/line_discipline.rs
View File

@ -265,6 +265,7 @@ impl LineDiscipline {
unreachable!()
}
};
self.pollee.invalidate();
Ok(read_len)
}
@ -344,6 +345,7 @@ impl LineDiscipline {
pub fn drain_input(&self) {
self.current_line.lock().drain();
self.read_buffer.lock().clear();
self.pollee.invalidate();
}
pub fn buffer_len(&self) -> usize {

5
kernel/src/fs/epoll/entry.rs
View File

@ -367,6 +367,11 @@ impl Iterator for ReadySetPopIter<'_> {
// must exist, so we can just unwrap it.
let weak_entry = entries.pop_front().unwrap();
// Clear the epoll file's events if there are no ready entries.
if entries.len() == 0 {
self.ready_set.pollee.invalidate();
}
let Some(entry) = Weak::upgrade(&weak_entry) else {
// The entry has been deleted.
continue;

10
kernel/src/fs/utils/channel.rs
View File

@ -225,6 +225,7 @@ impl Consumer<u8> {
let read_len = self.0.read(writer)?;
self.peer_end().pollee.notify(IoEvents::OUT);
self.this_end().pollee.invalidate();
if read_len > 0 {
Ok(read_len)
@ -248,6 +249,7 @@ impl<T: Pod> Consumer<T> {
let item = self.0.pop();
self.peer_end().pollee.notify(IoEvents::OUT);
self.this_end().pollee.invalidate();
if let Some(item) = item {
Ok(Some(item))
@ -331,12 +333,16 @@ impl<T> Common<T> {
let (rb_producer, rb_consumer) = rb.split();
let producer = {
let pollee = producer_pollee.unwrap_or_default();
let pollee = producer_pollee
.inspect(|pollee| pollee.invalidate())
.unwrap_or_default();
FifoInner::new(rb_producer, pollee)
};
let consumer = {
let pollee = consumer_pollee.unwrap_or_default();
let pollee = consumer_pollee
.inspect(|pollee| pollee.invalidate())
.unwrap_or_default();
FifoInner::new(rb_consumer, pollee)
};

8
kernel/src/net/socket/ip/datagram/mod.rs
View File

@ -157,9 +157,12 @@ impl DatagramSocket {
return_errno_with_message!(Errno::EAGAIN, "the socket is not bound");
};
bound_datagram
let recv_bytes = bound_datagram
.try_recv(writer, flags)
.map(|(recv_bytes, remote_endpoint)| (recv_bytes, remote_endpoint.into()))
.map(|(recv_bytes, remote_endpoint)| (recv_bytes, remote_endpoint.into()))?;
self.pollee.invalidate();
Ok(recv_bytes)
}
fn recv(
@ -190,6 +193,7 @@ impl DatagramSocket {
let iface_to_poll = bound_datagram.iface().clone();
drop(inner);
self.pollee.invalidate();
iface_to_poll.poll();
Ok(sent_bytes)

7
kernel/src/net/socket/ip/stream/mod.rs
View File

@ -248,6 +248,7 @@ impl StreamSocket {
});
drop(state);
self.pollee.invalidate();
if let Some(iface) = iface_to_poll {
iface.poll();
}
@ -286,6 +287,7 @@ impl StreamSocket {
let iface_to_poll = listen_stream.iface().clone();
drop(state);
self.pollee.invalidate();
iface_to_poll.poll();
accepted
@ -313,6 +315,7 @@ impl StreamSocket {
let remote_endpoint = connected_stream.remote_endpoint();
drop(state);
self.pollee.invalidate();
if let Some(iface) = iface_to_poll {
iface.poll();
}
@ -352,6 +355,7 @@ impl StreamSocket {
let iface_to_poll = need_poll.then(|| connected_stream.iface().clone());
drop(state);
self.pollee.invalidate();
if let Some(iface) = iface_to_poll {
iface.poll();
}
@ -498,6 +502,7 @@ impl Socket for StreamSocket {
}
};
self.pollee.invalidate();
(State::Listen(listen_stream), Ok(()))
})
}
@ -523,6 +528,8 @@ impl Socket for StreamSocket {
};
drop(state);
// No need to call `Pollee::invalidate` because `ConnectedStream::shutdown` will call
// `Pollee::notify`.
iface_to_poll.poll();
result

3
kernel/src/net/socket/unix/stream/listener.rs
View File

@ -38,6 +38,7 @@ impl Listener {
let backlog = BACKLOG_TABLE
.add_backlog(addr, reader_pollee, backlog, is_read_shutdown)
.unwrap();
writer_pollee.invalidate();
Self {
backlog,
@ -130,6 +131,8 @@ impl BacklogTable {
return None;
}
// Note that the cached events can be correctly inherited from `Init`, so there is no need
// to explicitly call `Pollee::invalidate`.
let new_backlog = Arc::new(Backlog::new(addr, pollee, backlog, is_shutdown));
backlog_sockets.insert(addr_key, new_backlog.clone());

1
kernel/src/net/socket/vsock/stream/connected.rs
View File

@ -56,6 +56,7 @@ impl Connected {
let mut connection = self.connection.disable_irq().lock();
let bytes_read = connection.buffer.read_fallible(writer)?;
connection.info.done_forwarding(bytes_read);
self.pollee.invalidate();
match bytes_read {
0 => {

1
kernel/src/net/socket/vsock/stream/listen.rs
View File

@ -51,6 +51,7 @@ impl Listen {
.ok_or_else(|| {
Error::with_message(Errno::EAGAIN, "no pending connection is available")
})?;
self.pollee.invalidate();
Ok(connection)
}

251
kernel/src/process/signal/poll.rs
View File

@ -1,11 +1,14 @@
// SPDX-License-Identifier: MPL-2.0
use core::{
sync::atomic::{AtomicUsize, Ordering},
sync::atomic::{AtomicIsize, AtomicUsize, Ordering},
time::Duration,
};
use ostd::sync::{Waiter, Waker};
use ostd::{
sync::{Waiter, Waker},
task::Task,
};
use crate::{
events::{IoEvents, Observer, Subject},
@ -18,7 +21,10 @@ use crate::{
/// 1. An I/O object to maintain its I/O readiness; and
/// 2. An interested part to poll the object's I/O readiness.
///
/// To correctly use the pollee, you need to call [`Pollee::notify`] whenever a new event arrives.
/// To use the pollee correctly, you must follow the rules below carefully:
/// * [`Pollee::notify`] needs to be called whenever a new event arrives.
/// * [`Pollee::invalidate`] needs to be called whenever an old event disappears and no new event
/// arrives.
///
/// Then, [`Pollee::poll_with`] can allow you to register a [`Poller`] to wait for certain events,
/// or register a [`PollAdaptor`] to be notified when certain events occur.
@ -26,9 +32,28 @@ pub struct Pollee {
inner: Arc<PolleeInner>,
}
const INV_STATE: isize = -1;
struct PolleeInner {
// A subject which is monitored with pollers.
/// A subject which is monitored with pollers.
subject: Subject<IoEvents, IoEvents>,
/// A state that describes how events are cached in the pollee.
///
/// The meaning of this field depends on its value:
///
/// * A non-negative value represents cached events. The events are guaranteed to be
/// up-to-date, i.e., no one has called [`Pollee::notify`] or [`Pollee::invalidate`] since we
/// started checking the events.
///
/// * A value of [`INV_STATE`] means no cached events. We may have previously cached some
/// events, but they are no longer valid due to calls of [`Pollee::notify`] or
/// [`Pollee::invalidate`].
///
/// * A negative value other than [`INV_STATE`] represents a [`Task`] that is currently
/// checking events. When the task has finished checking and the state is neither invalidated
/// nor overwritten by another task checking events, the state can be used to cache the
/// checked events.
state: AtomicIsize,
}
impl Default for Pollee {
@ -42,6 +67,7 @@ impl Pollee {
pub fn new() -> Self {
let inner = PolleeInner {
subject: Subject::new(),
state: AtomicIsize::new(INV_STATE),
};
Self {
inner: Arc::new(inner),
@ -75,8 +101,52 @@ impl Pollee {
self.register_poller(poller, mask);
}
// Return the cached events, if any.
let events = self.inner.state.load(Ordering::Acquire);
if events >= 0 {
return IoEvents::from_bits_truncate(events as _) & mask;
}
// If we know some task is checking the events, let it finish.
if events != INV_STATE {
return check() & mask;
}
// We will store `task_ptr` in `state` to indicate that we're checking the events. But we
// need to make sure it's a negative value.
const {
use ostd::mm::KERNEL_VADDR_RANGE;
assert!((KERNEL_VADDR_RANGE.start as isize) < 0);
}
let task_ptr = Task::current().unwrap().as_ref() as *const _ as isize;
// Store `task_ptr` in `state` to indicate we're checking the events.
//
// Note that:
// * If there are race conditions, `state` may contain something other than `INV_STATE` (as
// checked above), but that's okay.
// * Given the first point, we only need to do a store here. However, we need the `Acquire`
// order, which forces us to do a `swap` operation. We ignore the returned value to allow
// the compiler to produce better assembly code.
let _ = self.inner.state.swap(task_ptr, Ordering::Acquire);
// Check events after the registration to prevent race conditions.
check() & mask
let new_events = check();
// If this `compare_exchange_weak` succeeds, we can guarantee that we are the only task
// trying to cache the checked events, and that the events are not invalidated in the
// middle, so we can cache them with confidence.
//
// Otherwise, we cache nothing, but returning the obsolete events is still okay.
let _ = self.inner.state.compare_exchange_weak(
task_ptr,
new_events.bits() as _,
Ordering::Release,
Ordering::Relaxed,
);
// Return the events filtered by the mask.
new_events & mask
}
fn register_poller(&self, poller: &mut PollHandle, mask: IoEvents) {
@ -89,13 +159,27 @@ impl Pollee {
/// Notifies pollers of some events.
///
/// This method wakes up all registered pollers that are interested in the events.
/// This method invalidates the (internal) cached events and wakes up all registered pollers
/// that are interested in the events.
///
/// The events can be spurious. This way, the caller can avoid expensive calculations and
/// simply add all possible ones.
/// This method should be called whenever new events arrive. The events can be spurious. This
/// way, the caller can avoid expensive calculations and simply add all possible ones.
pub fn notify(&self, events: IoEvents) {
self.invalidate();
self.inner.subject.notify_observers(&events);
}
/// Invalidates the (internal) cached events.
///
/// This method should be called whenever old events disappear but no new events arrive. The
/// invalidation can be spurious, so the caller can avoid complex calculations and simply
/// invalidate even if no events disappear.
pub fn invalidate(&self) {
// The memory order must be `Release`, so that the reader is guaranteed to see the changes
// that trigger the invalidation.
self.inner.state.store(INV_STATE, Ordering::Release);
}
}
/// An opaque handle that can be used as an argument of the [`Pollable::poll`] method.
@ -325,3 +409,154 @@ pub trait Pollable {
}
}
}
#[cfg(ktest)]
mod test {
use ostd::prelude::*;
use super::*;
#[ktest]
fn test_notify_before() {
let pollee = Pollee::new();
pollee.notify(IoEvents::OUT);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::IN),
// This is allowed, as we invoke the checking closure.
IoEvents::IN
);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as the cached state is still valid.
IoEvents::IN
);
}
#[ktest]
fn test_notify_middle() {
let pollee = Pollee::new();
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || {
pollee.notify(IoEvents::OUT);
IoEvents::IN
}),
// This is allowed, as we invoke the checking closure.
IoEvents::IN
);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as we invoke the checking closure.
//
// Reusing the cached state is NOT allowed as we've been notified above.
IoEvents::OUT
);
}
#[ktest]
fn test_notify_after() {
let pollee = Pollee::new();
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::IN),
// This is allowed, as we invoke the checking closure.
IoEvents::IN
);
pollee.notify(IoEvents::OUT);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as we invoke the checking closure.
//
// Reusing the cached state is NOT allowed as we've been notified above.
IoEvents::OUT
);
}
#[ktest]
fn test_nested_notify_before() {
let pollee = Pollee::new();
pollee.notify(IoEvents::OUT);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || {
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as we invoke the checking closure.
IoEvents::OUT
);
IoEvents::IN
}),
// This is allowed, as we invoke the checking closure.
IoEvents::IN
);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as the cached state is still valid.
IoEvents::IN
);
}
#[ktest]
fn test_nested_notify_between() {
let pollee = Pollee::new();
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || {
pollee.notify(IoEvents::OUT);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as we invoke the checking closure.
IoEvents::OUT
);
IoEvents::IN
}),
// This is allowed, as we invoke the checking closure.
IoEvents::IN
);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as we invoke the checking closure.
//
// Reusing the cached state is NOT allowed as we've been notified above.
IoEvents::OUT
);
}
#[ktest]
fn test_nested_notify_inside() {
let pollee = Pollee::new();
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || {
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || {
pollee.notify(IoEvents::OUT);
IoEvents::OUT
}),
// This is allowed, as we invoke the checking closure.
IoEvents::OUT
);
IoEvents::IN
}),
// This is allowed, as we invoke the checking closure.
IoEvents::IN
);
assert_eq!(
pollee.poll_with(IoEvents::all(), None, || IoEvents::OUT),
// This is allowed, as we invoke the checking closure.
//
// Reusing the cached state is NOT allowed as we've been notified above.
IoEvents::OUT,
);
}
}

3
ostd/src/mm/mod.rs
View File

@ -100,9 +100,10 @@ pub(crate) const fn nr_base_per_page<C: PagingConstsTrait>(level: PagingLevel) -
pub const MAX_USERSPACE_VADDR: Vaddr = 0x0000_8000_0000_0000 - PAGE_SIZE;
/// The kernel address space.
///
/// There are the high canonical addresses defined in most 48-bit width
/// architectures.
pub(crate) const KERNEL_VADDR_RANGE: Range<Vaddr> = 0xffff_8000_0000_0000..0xffff_ffff_ffff_0000;
pub const KERNEL_VADDR_RANGE: Range<Vaddr> = 0xffff_8000_0000_0000..0xffff_ffff_ffff_0000;
/// Gets physical address trait
pub trait HasPaddr {