Make wait_events support timeout

kernel/src/device/pty/pty.rs

@@ -138,7 +138,7 @@ impl FileIo for PtyMaster {
         }
 
         // TODO: deal with nonblocking and timeout
-        self.wait_events(IoEvents::IN, || self.try_read(writer))
+        self.wait_events(IoEvents::IN, None, || self.try_read(writer))
     }
 
     fn write(&self, reader: &mut VmReader) -> Result<usize> {

kernel/src/device/tty/line_discipline.rs

@@ -235,7 +235,7 @@ impl LineDiscipline {
     }
 
     pub fn read(&self, buf: &mut [u8]) -> Result<usize> {
-        self.wait_events(IoEvents::IN, || self.try_read(buf))
+        self.wait_events(IoEvents::IN, None, || self.try_read(buf))
     }
 
     /// Reads all bytes buffered to `dst`.

kernel/src/fs/epoll/epoll_file.rs

@@ -194,34 +194,21 @@ impl EpollFile {
     /// expires or a signal arrives.
     pub fn wait(&self, max_events: usize, timeout: Option<&Duration>) -> Result<Vec<EpollEvent>> {
         let mut ep_events = Vec::new();
-        let mut poller = None;
-        loop {
-            // Try to pop some ready entries
+
+        self.wait_events(IoEvents::IN, timeout, || {
             self.pop_multi_ready(max_events, &mut ep_events);
-            if !ep_events.is_empty() {
-                return Ok(ep_events);
+
+            if ep_events.is_empty() {
+                return Err(Error::with_message(
+                    Errno::EAGAIN,
+                    "there are no available events",
+                ));
             }
 
-            // Return immediately if specifying a timeout of zero
-            if timeout.is_some() && timeout.as_ref().unwrap().is_zero() {
-                return Ok(ep_events);
-            }
+            Ok(())
+        })?;
 
-            // If no ready entries for now, wait for them
-            if poller.is_none() {
-                poller = Some(Poller::new());
-                let events = self.pollee.poll(IoEvents::IN, poller.as_mut());
-                if !events.is_empty() {
-                    continue;
-                }
-            }
-
-            if let Some(timeout) = timeout {
-                poller.as_ref().unwrap().wait_timeout(timeout)?;
-            } else {
-                poller.as_ref().unwrap().wait()?;
-            }
-        }
+        Ok(ep_events)
     }
 
     fn push_ready(&self, entry: Arc<EpollEntry>) {

kernel/src/fs/pipe.rs

@@ -63,7 +63,7 @@ impl FileLike for PipeReader {
         let read_len = if self.status_flags().contains(StatusFlags::O_NONBLOCK) {
             self.consumer.try_read(writer)?
         } else {
-            self.wait_events(IoEvents::IN, || self.consumer.try_read(writer))?
+            self.wait_events(IoEvents::IN, None, || self.consumer.try_read(writer))?
         };
         Ok(read_len)
     }
@@ -148,7 +148,7 @@ impl FileLike for PipeWriter {
         if self.status_flags().contains(StatusFlags::O_NONBLOCK) {
             self.producer.try_write(reader)
         } else {
-            self.wait_events(IoEvents::OUT, || self.producer.try_write(reader))
+            self.wait_events(IoEvents::OUT, None, || self.producer.try_write(reader))
         }
     }
 

kernel/src/net/socket/ip/datagram/mod.rs

@@ -175,7 +175,7 @@ impl DatagramSocket {
         if self.is_nonblocking() {
             self.try_recv(writer, flags)
         } else {
-            self.wait_events(IoEvents::IN, || self.try_recv(writer, flags))
+            self.wait_events(IoEvents::IN, None, || self.try_recv(writer, flags))
         }
     }
 

kernel/src/net/socket/ip/stream/mod.rs

@@ -318,7 +318,7 @@ impl StreamSocket {
         if self.is_nonblocking() {
             self.try_recv(writer, flags)
         } else {
-            self.wait_events(IoEvents::IN, || self.try_recv(writer, flags))
+            self.wait_events(IoEvents::IN, None, || self.try_recv(writer, flags))
         }
     }
 
@@ -350,7 +350,7 @@ impl StreamSocket {
         if self.is_nonblocking() {
             self.try_send(reader, flags)
         } else {
-            self.wait_events(IoEvents::OUT, || self.try_send(reader, flags))
+            self.wait_events(IoEvents::OUT, None, || self.try_send(reader, flags))
         }
     }
 
@@ -479,7 +479,7 @@ impl Socket for StreamSocket {
             return result;
         }
 
-        self.wait_events(IoEvents::OUT, || self.check_connect())
+        self.wait_events(IoEvents::OUT, None, || self.check_connect())
     }
 
     fn listen(&self, backlog: usize) -> Result<()> {
@@ -518,7 +518,7 @@ impl Socket for StreamSocket {
         if self.is_nonblocking() {
             self.try_accept()
         } else {
-            self.wait_events(IoEvents::IN, || self.try_accept())
+            self.wait_events(IoEvents::IN, None, || self.try_accept())
         }
     }
 

kernel/src/net/socket/unix/stream/socket.rs

@@ -69,7 +69,7 @@ impl UnixStreamSocket {
         if self.is_nonblocking() {
             self.try_send(reader, flags)
         } else {
-            self.wait_events(IoEvents::OUT, || self.try_send(reader, flags))
+            self.wait_events(IoEvents::OUT, None, || self.try_send(reader, flags))
         }
     }
 
@@ -86,7 +86,7 @@ impl UnixStreamSocket {
         if self.is_nonblocking() {
             self.try_recv(writer, flags)
         } else {
-            self.wait_events(IoEvents::IN, || self.try_recv(writer, flags))
+            self.wait_events(IoEvents::IN, None, || self.try_recv(writer, flags))
         }
     }
 
@@ -296,7 +296,7 @@ impl Socket for UnixStreamSocket {
         if self.is_nonblocking() {
             self.try_accept()
         } else {
-            self.wait_events(IoEvents::IN, || self.try_accept())
+            self.wait_events(IoEvents::IN, None, || self.try_accept())
         }
     }
 

kernel/src/net/socket/vsock/stream/socket.rs

@@ -125,7 +125,7 @@ impl VsockStreamSocket {
         if self.is_nonblocking() {
             self.try_recv(writer, flags)
         } else {
-            self.wait_events(IoEvents::IN, || self.try_recv(writer, flags))
+            self.wait_events(IoEvents::IN, None, || self.try_recv(writer, flags))
         }
     }
 }
@@ -236,7 +236,7 @@ impl Socket for VsockStreamSocket {
             .poll(IoEvents::IN, Some(&mut poller))
             .contains(IoEvents::IN)
         {
-            if let Err(e) = poller.wait() {
+            if let Err(e) = poller.wait(None) {
                 vsockspace
                     .remove_connecting_socket(&connecting.local_addr())
                     .unwrap();
@@ -285,7 +285,7 @@ impl Socket for VsockStreamSocket {
         if self.is_nonblocking() {
             self.try_accept()
         } else {
-            self.wait_events(IoEvents::IN, || self.try_accept())
+            self.wait_events(IoEvents::IN, None, || self.try_accept())
         }
     }
 

kernel/src/process/signal/poll.rs

@@ -158,17 +158,12 @@ impl Poller {
         }
     }
 
-    /// Wait until there are any interesting events happen since last `wait`. The `wait`
-    /// can be interrupted by signal.
-    pub fn wait(&self) -> Result<()> {
-        self.event_counter.read(&self.waiter, None)?;
-        Ok(())
-    }
-
-    /// Wait until there are any interesting events happen since last `wait` or a given timeout
-    /// is expired. This method can be interrupted by signal.
-    pub fn wait_timeout(&self, timeout: &Duration) -> Result<()> {
-        self.event_counter.read(&self.waiter, Some(timeout))?;
+    /// Waits until some interesting events happen since the last wait or until the timeout
+    /// expires.
+    ///
+    /// The waiting process can be interrupted by a signal.
+    pub fn wait(&self, timeout: Option<&Duration>) -> Result<()> {
+        self.event_counter.read(&self.waiter, timeout)?;
         Ok(())
     }
 
@@ -256,29 +251,52 @@ pub trait Pollable {
     /// will return whatever the call to `cond()` returns. Otherwise, the method will wait for some
     /// interesting events specified in `mask` to happen and try again.
     ///
+    /// This method will fail with `ETIME` if the timeout is specified and the event does not occur
+    /// before the timeout expires.
+    ///
     /// The user must ensure that a call to `cond()` does not fail with `EAGAIN` when the
     /// interesting events occur. However, it is allowed to have spurious `EAGAIN` failures due to
     /// race conditions where the events are consumed by another thread.
-    fn wait_events<F, R>(&self, mask: IoEvents, mut cond: F) -> Result<R>
+    fn wait_events<F, R>(
+        &self,
+        mask: IoEvents,
+        timeout: Option<&Duration>,
+        mut cond: F,
+    ) -> Result<R>
     where
         Self: Sized,
         F: FnMut() -> Result<R>,
     {
+        // Fast path: Return immediately if the operation gives a result.
+        match cond() {
+            Err(err) if err.error() == Errno::EAGAIN => (),
+            result => return result,
+        }
+
+        // Fast path: Return immediately if the timeout is zero.
+        if timeout.is_some_and(|duration| duration.is_zero()) {
+            return_errno_with_message!(Errno::ETIME, "the timeout expired");
+        }
+
+        // Wait until the event happens.
         let mut poller = Poller::new();
+        if self.poll(mask, Some(&mut poller)).is_empty() {
+            poller.wait(timeout)?;
+        }
 
         loop {
+            // Try again after the event happens.
             match cond() {
                 Err(err) if err.error() == Errno::EAGAIN => (),
                 result => return result,
             };
 
-            let events = self.poll(mask, Some(&mut poller));
-            if !events.is_empty() {
-                continue;
+            // 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)?;
             }
-
-            // TODO: Support timeout
-            poller.wait()?;
         }
     }
 }

kernel/src/syscall/eventfd.rs

@@ -190,7 +190,7 @@ impl FileLike for EventFile {
         if self.is_nonblocking() {
             self.try_read(writer)?;
         } else {
-            self.wait_events(IoEvents::IN, || self.try_read(writer))?;
+            self.wait_events(IoEvents::IN, None, || self.try_read(writer))?;
         }
 
         Ok(read_len)

kernel/src/syscall/poll.rs

@@ -41,7 +41,7 @@ pub fn sys_poll(fds: Vaddr, nfds: u64, timeout: i32, ctx: &Context) -> Result<Sy
         poll_fds, nfds, timeout
     );
 
-    let num_revents = do_poll(&poll_fds, timeout, ctx)?;
+    let num_revents = do_poll(&poll_fds, timeout.as_ref(), ctx)?;
 
     // Write back
     let mut write_addr = fds;
@@ -55,7 +55,7 @@ pub fn sys_poll(fds: Vaddr, nfds: u64, timeout: i32, ctx: &Context) -> Result<Sy
     Ok(SyscallReturn::Return(num_revents as _))
 }
 
-pub fn do_poll(poll_fds: &[PollFd], timeout: Option<Duration>, ctx: &Context) -> Result<usize> {
+pub fn do_poll(poll_fds: &[PollFd], timeout: Option<&Duration>, ctx: &Context) -> Result<usize> {
     let (result, files) = hold_files(poll_fds, ctx);
     match result {
         FileResult::AllValid => (),
@@ -74,24 +74,22 @@ pub fn do_poll(poll_fds: &[PollFd], timeout: Option<Duration>, ctx: &Context) ->
     };
 
     loop {
-        if let Some(timeout) = timeout.as_ref() {
-            match poller.wait_timeout(timeout) {
-                Ok(_) => {}
-                Err(e) if e.error() == Errno::ETIME => {
-                    // The return value is zero if the timeout expires
-                    // before any file descriptors became ready
-                    return Ok(0);
-                }
-                Err(e) => return Err(e),
-            };
-        } else {
-            poller.wait()?;
-        }
+        match poller.wait(timeout) {
+            Ok(_) => {}
+            Err(e) if e.error() == Errno::ETIME => {
+                // The return value is zero if the timeout expires
+                // before any file descriptors became ready
+                return Ok(0);
+            }
+            Err(e) => return Err(e),
+        };
 
         let num_events = count_all_events(poll_fds, &files);
         if num_events > 0 {
             return Ok(num_events);
         }
+
+        // FIXME: We need to update `timeout` since we have waited for some time.
     }
 }
 

kernel/src/syscall/select.rs

@@ -72,7 +72,7 @@ pub fn do_sys_select(
         readfds.as_mut(),
         writefds.as_mut(),
         exceptfds.as_mut(),
-        timeout,
+        timeout.as_ref(),
         ctx,
     )?;
 
@@ -100,7 +100,7 @@ fn do_select(
     mut readfds: Option<&mut FdSet>,
     mut writefds: Option<&mut FdSet>,
     mut exceptfds: Option<&mut FdSet>,
-    timeout: Option<Duration>,
+    timeout: Option<&Duration>,
     ctx: &Context,
 ) -> Result<usize> {
     // Convert the FdSet to an array of PollFd