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Revise the poll() method

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This commit is contained in:
Ruihan Li 2024-08-31 22:35:40 +08:00 committed by Tate, Hongliang Tian
parent 1469059888
commit 44b55f2ccf
1 changed files with 12 additions and 19 deletions
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29
kernel/src/process/signal/poll.rs
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@ -37,27 +37,22 @@ impl Pollee {
}
}
/// Returns the current events of the pollee given an event mask.
/// Returns the current events of the pollee filtered by the given event mask.
///
/// If no interesting events are polled and a poller is provided, then
/// the poller will start monitoring the pollee and receive event
/// notification once the pollee gets any interesting events.
/// If a poller is provided, the poller will start monitoring the pollee and receive event
/// notification when the pollee receives interesting events.
///
/// This operation is _atomic_ in the sense that either some interesting
/// events are returned or the poller is registered (if a poller is provided).
/// This operation is _atomic_ in the sense that if there are interesting events, either the
/// events are returned or the poller is notified.
pub fn poll(&self, mask: IoEvents, poller: Option<&mut Poller>) -> IoEvents {
let mask = mask | IoEvents::ALWAYS_POLL;
// Fast path: return events immediately
let revents = self.events() & mask;
if !revents.is_empty() || poller.is_none() {
return revents;
// Register the provided poller.
if let Some(poller) = poller {
self.register_poller(poller, mask);
}
// Register the provided poller.
self.register_poller(poller.unwrap(), mask);
// It is important to check events again to handle race conditions
// Check events after the registration to prevent race conditions.
self.events() & mask
}
@ -235,8 +230,8 @@ impl Observer<IoEvents> for EventCounter {
/// have access to the internal [`Pollee`], but there is a method that provides the same semantics
/// as [`Pollee::poll`] and we need to perform event-based operations using that method.
pub trait Pollable {
/// Returns the interesting events if there are any, or waits for them to happen if there are
/// none.
/// Returns the interesting events now and monitors their occurrence in the future if the
/// poller is provided.
///
/// This method has the same semantics as [`Pollee::poll`].
fn poll(&self, mask: IoEvents, poller: Option<&mut Poller>) -> IoEvents;
@ -290,9 +285,7 @@ pub trait Pollable {
// Wait until the next event happens.
//
// FIXME: We need to update `timeout` since we have waited for some time.
if self.poll(mask, Some(&mut poller)).is_empty() {
poller.wait(timeout)?;
}
}
}
}