diff --git a/src/Enclave.edl b/src/Enclave.edl
index 4b4c7a7e..1fba2881 100644
--- a/src/Enclave.edl
+++ b/src/Enclave.edl
@@ -190,6 +190,15 @@ enclave {
             unsigned int initval,
             int flags
         ) propagate_errno;
+        int occlum_ocall_eventfd_poll(
+            int eventfd,
+            [in, out] struct timespec *timeout
+        ) propagate_errno;
+        void occlum_ocall_eventfd_write_batch(
+            [in, count=num_fds] int* eventfds,
+            size_t num_fds,
+            uint64_t val
+        );
 
         int occlum_ocall_poll(
             [in, out, count=nfds] struct pollfd *fds,
diff --git a/src/libos/src/events/event.rs b/src/libos/src/events/event.rs
new file mode 100644
index 00000000..f012e020
--- /dev/null
+++ b/src/libos/src/events/event.rs
@@ -0,0 +1,7 @@
+/// A trait to represent any event.
+pub trait Event: Copy + Clone + Send + Sync + 'static {}
+
+/// A trait to filter events.
+pub trait EventFilter<E: Event>: Send + Sync + 'static {
+    fn filter(&self, event: &E) -> bool;
+}
diff --git a/src/libos/src/events/host_event_fd.rs b/src/libos/src/events/host_event_fd.rs
new file mode 100644
index 00000000..aff80a19
--- /dev/null
+++ b/src/libos/src/events/host_event_fd.rs
@@ -0,0 +1,111 @@
+use std::time::Duration;
+
+use crate::prelude::*;
+use crate::time::{timespec_t, TIMERSLACK};
+
+pub struct HostEventFd {
+    host_fd: FileDesc,
+}
+
+impl HostEventFd {
+    pub fn new() -> Result<Self> {
+        const EFD_NONBLOCK: i32 = 1 << 11;
+        let host_fd = try_libc!({
+            let mut ret: i32 = 0;
+            let status = occlum_ocall_eventfd(&mut ret, 0, EFD_NONBLOCK);
+            assert!(status == sgx_status_t::SGX_SUCCESS);
+            ret
+        }) as FileDesc;
+        Ok(Self { host_fd })
+    }
+
+    pub fn read_u64(&self) -> Result<u64> {
+        let mut val: u64 = 0;
+        let ret = try_libc!(libc::ocall::read(
+            self.host_fd as c_int,
+            &mut val as *mut _ as *mut c_void,
+            std::mem::size_of::<u64>(),
+        )) as usize;
+        debug_assert!(ret != std::mem::size_of::<u64>());
+        Ok(val)
+    }
+
+    pub fn write_u64(&self, val: u64) {
+        unsafe {
+            libc::ocall::write(
+                self.host_fd as c_int,
+                &val as *const _ as *const c_void,
+                std::mem::size_of::<u64>(),
+            );
+        }
+    }
+
+    pub fn poll(&self, timeout: Option<&Duration>) -> Result<()> {
+        let mut timeout = timeout.cloned();
+        self.poll_mut(timeout.as_mut())
+    }
+
+    pub fn poll_mut(&self, timeout: Option<&mut Duration>) -> Result<()> {
+        match timeout {
+            None => ocall_eventfd_poll(self.host_fd, std::ptr::null_mut()),
+            Some(timeout) => {
+                let mut remain_c = timespec_t::from(*timeout);
+                let ret = ocall_eventfd_poll(self.host_fd, &mut remain_c);
+
+                let remain = remain_c.as_duration();
+                assert!(remain <= *timeout + TIMERSLACK.to_duration());
+                *timeout = remain;
+
+                ret
+            }
+        }
+    }
+
+    /// Write to all host eventfds in one OCall.
+    ///
+    /// Precondition. The caller must ensure that the host fds are valid.
+    pub unsafe fn write_u64_raw_and_batch(host_fds: &[FileDesc], val: u64) {
+        ocall_eventfd_write_batch(host_fds, val);
+    }
+
+    pub fn host_fd(&self) -> FileDesc {
+        self.host_fd
+    }
+}
+
+impl Drop for HostEventFd {
+    fn drop(&mut self) {
+        let ret = unsafe { libc::ocall::close(self.host_fd as c_int) };
+        debug_assert!(ret == 0);
+    }
+}
+
+fn ocall_eventfd_poll(host_fd: FileDesc, timeout: *mut timespec_t) -> Result<()> {
+    try_libc!({
+        let mut ret = 0;
+        let status = unsafe { occlum_ocall_eventfd_poll(&mut ret, host_fd, timeout) };
+        assert!(status == sgx_status_t::SGX_SUCCESS);
+        ret
+    });
+    Ok(())
+}
+
+fn ocall_eventfd_write_batch(host_fds: &[FileDesc], val: u64) {
+    let status =
+        unsafe { occlum_ocall_eventfd_write_batch(host_fds.as_ptr(), host_fds.len(), val) };
+    assert!(status == sgx_status_t::SGX_SUCCESS);
+}
+
+extern "C" {
+    fn occlum_ocall_eventfd(ret: *mut i32, init_val: u32, flags: i32) -> sgx_status_t;
+    fn occlum_ocall_eventfd_poll(
+        ret: *mut i32,
+        fd: FileDesc,
+        timeout: *mut timespec_t,
+    ) -> sgx_status_t;
+    fn occlum_ocall_eventfd_write_batch(
+        fds: *const FileDesc,
+        num_fds: usize,
+        val: u64,
+    ) -> sgx_status_t;
+}
diff --git a/src/libos/src/events/mod.rs b/src/libos/src/events/mod.rs
new file mode 100644
index 00000000..099ca50c
--- /dev/null
+++ b/src/libos/src/events/mod.rs
@@ -0,0 +1,32 @@
+//! The event subsystem.
+//!
+//! An event can be anything ranging from the exit of a process (interesting
+//! to `wait4`) to the arrival of a blocked signal (interesting to `sigwaitinfo`),
+//! from the completion of a file operation (interesting to `epoll`) to the change
+//! of a file status (interesting to `inotify`).
+//!
+//! To meet the event-related demands from various subsystems, this event
+//! subsystem is designed to provide a set of general-purpose primitives:
+//!
+//! * `Waiter`, `Waker`, and `WaiterQueue` are primitives to put threads to sleep
+//! and later wake them up.
+//! * `Event`, `Observer`, and `Notifier` are primitives to handle and broadcast
+//! events.
+//! * `WaiterQueueObserver` implements the common pattern of waking up threads
+//! * once some interesting events happen.
+
+mod event;
+mod host_event_fd;
+mod notifier;
+mod observer;
+mod waiter;
+mod waiter_queue;
+mod waiter_queue_observer;
+
+pub use self::event::{Event, EventFilter};
+pub use self::host_event_fd::HostEventFd;
+pub use self::notifier::Notifier;
+pub use self::observer::Observer;
+pub use self::waiter::{Waiter, Waker};
+pub use self::waiter_queue::WaiterQueue;
+pub use self::waiter_queue_observer::WaiterQueueObserver;
diff --git a/src/libos/src/events/notifier.rs b/src/libos/src/events/notifier.rs
new file mode 100644
index 00000000..9e51249d
--- /dev/null
+++ b/src/libos/src/events/notifier.rs
@@ -0,0 +1,75 @@
+use std::any::Any;
+use std::marker::PhantomData;
+use std::sync::Weak;
+
+use super::{Event, EventFilter, Observer};
+use crate::prelude::*;
+
+/// An event notifier broadcasts interesting events to registered observers.
+pub struct Notifier<E: Event, F: EventFilter<E> = DummyEventFilter<E>> {
+    subscribers: SgxMutex<VecDeque<Subscriber<E, F>>>,
+}
+
+struct Subscriber<E: Event, F: EventFilter<E>> {
+    observer: Weak<dyn Observer<E>>,
+    filter: Option<F>,
+    metadata: Option<Box<dyn Any + Send + Sync>>,
+}
+
+impl<E: Event, F: EventFilter<E>> Notifier<E, F> {
+    /// Create an event notifier.
+    pub fn new() -> Self {
+        let subscribers = SgxMutex::new(VecDeque::new());
+        Self { subscribers }
+    }
+
+    /// Register an observer with its interesting events and metadata.
+    pub fn register(
+        &self,
+        observer: Weak<dyn Observer<E>>,
+        filter: Option<F>,
+        metadata: Option<Box<dyn Any + Send + Sync>>,
+    ) {
+        let mut subscribers = self.subscribers.lock().unwrap();
+        subscribers.push_back(Subscriber {
+            observer,
+            filter,
+            metadata,
+        });
+    }
+
+    /// Unregister an observer.
+    pub fn unregister(&self, observer: &Weak<dyn Observer<E>>) {
+        let mut subscribers = self.subscribers.lock().unwrap();
+        subscribers.retain(|subscriber| !Weak::ptr_eq(&subscriber.observer, observer));
+    }
+
+    /// Broadcast an event to all registered observers.
+    pub fn broadcast(&self, event: &E) {
+        let subscribers = self.subscribers.lock().unwrap();
+        for subscriber in subscribers.iter() {
+            if let Some(filter) = subscriber.filter.as_ref() {
+                if !filter.filter(event) {
+                    continue;
+                }
+            }
+            let observer = match subscriber.observer.upgrade() {
+                // TODO: should remove subscribers whose observers have been freed
+                None => return,
+                Some(observer) => observer,
+            };
+
+            observer.on_event(event, &subscriber.metadata);
+        }
+    }
+}
+
+pub struct DummyEventFilter<E> {
+    phantom: PhantomData<E>,
+}
+
+impl<E: Event> EventFilter<E> for DummyEventFilter<E> {
+    fn filter(&self, event: &E) -> bool {
+        true
+    }
+}
diff --git a/src/libos/src/events/observer.rs b/src/libos/src/events/observer.rs
new file mode 100644
index 00000000..8a219835
--- /dev/null
+++ b/src/libos/src/events/observer.rs
@@ -0,0 +1,19 @@
+use std::any::Any;
+
+use super::Event;
+use crate::prelude::*;
+
+/// An obsever receives events from the notifiers to which it has registered.
+pub trait Observer<E: Event>: Send + Sync {
+    /// The callback that will be executed when some interesting events are
+    /// delivered by a notifier to this observer.
+    ///
+    /// Note that it is important to keep this method simple, short, and
+    /// non-blocking. This is because the caller of this function, which is most
+    /// likely to be `Notifier::broadcast`, may have acquired the locks of some
+    /// resources. In general, these locks may coincide with the ones required
+    /// by a specific implementation of `Observer::on_event`. Thus, to avoid
+    /// the odds of deadlocks, the `on_event` method should be written short
+    /// and sweet.
+    fn on_event(&self, event: &E, metadata: &Option<Box<dyn Any + Send + Sync>>) -> ();
+}
diff --git a/src/libos/src/events/waiter.rs b/src/libos/src/events/waiter.rs
new file mode 100644
index 00000000..a7eceaf3
--- /dev/null
+++ b/src/libos/src/events/waiter.rs
@@ -0,0 +1,172 @@
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Weak;
+use std::time::Duration;
+
+use super::host_event_fd::HostEventFd;
+use crate::prelude::*;
+
+/// A waiter enables a thread to sleep.
+pub struct Waiter {
+    inner: Arc<Inner>,
+}
+
+impl Waiter {
+    /// Create a waiter for the current thread.
+    ///
+    /// A `Waiter` is bound to the curent thread that creates it: it cannot be
+    /// sent to or used by any other threads as the type implements `!Send` and
+    /// `!Sync` traits. Thus, a `Waiter` can only put the current thread to sleep.
+    pub fn new() -> Self {
+        Self {
+            inner: Arc::new(Inner::new()),
+        }
+    }
+
+    /// Return whether a waiter has been waken up.
+    ///
+    /// Once a waiter is waken up, the `wait` or `wait_mut` method becomes
+    /// non-blocking.
+    pub fn is_woken(&self) -> bool {
+        self.inner.is_woken()
+    }
+
+    /// Reset a waiter.
+    ///
+    /// After a `Waiter` being waken up, the `reset` method must be called so
+    /// that the `Waiter` can use the `wait` or `wait_mut` methods to sleep the
+    /// current thread again.
+    pub fn reset(&self) {
+        self.inner.reset();
+    }
+
+    /// Put the current thread to sleep until being waken up by a waker.
+    ///
+    /// The method has three possible return values:
+    /// 1. `Ok(())`: The `Waiter` has been waken up by one of its `Waker`;
+    /// 2. `Err(e) if e.errno() == Errno::ETIMEDOUT`: Timeout.
+    /// 3. `Err(e) if e.errno() == Errno::EINTR`: Interrupted by a signal.
+    ///
+    /// If the `timeout` argument is `None`, then the second case won't happen,
+    /// i.e., the method will block indefinitely.
+    pub fn wait(&self, timeout: Option<&Duration>) -> Result<()> {
+        self.inner.wait(timeout)
+    }
+
+    /// Put the current thread to sleep until being waken up by a waker.
+    ///
+    /// This method is similar to the `wait` method except that the `timeout`
+    /// argument will be updated to reflect the remaining timeout.
+    pub fn wait_mut(&self, timeout: Option<&mut Duration>) -> Result<()> {
+        self.inner.wait_mut(timeout)
+    }
+
+    /// Create a waker that can wake up this waiter.
+    ///
+    /// `WaiterQueue` maintains a list of `Waker` internally to wake up the
+    /// enqueued `Waiter`s. So, for users that uses `WaiterQueue`, this method
+    /// does not need to be called manually.
+    pub fn waker(&self) -> Waker {
+        Waker {
+            inner: Arc::downgrade(&self.inner),
+        }
+    }
+}
+
+impl !Send for Waiter {}
+impl !Sync for Waiter {}
+
+/// A waker can wake up the thread that its waiter has put to sleep.
+pub struct Waker {
+    inner: Weak<Inner>,
+}
+
+impl Waker {
+    /// Wake up the waiter that creates this waker.
+    pub fn wake(&self) {
+        if let Some(inner) = self.inner.upgrade() {
+            inner.wake()
+        }
+    }
+
+    /// Wake up waiters in batch, more efficient than waking up one-by-one.
+    pub fn batch_wake<'a, I: Iterator<Item = &'a Waker>>(iter: I) {
+        Inner::batch_wake(iter);
+    }
+}
+
+struct Inner {
+    is_woken: AtomicBool,
+    host_eventfd: Arc<HostEventFd>,
+}
+
+impl Inner {
+    pub fn new() -> Self {
+        let is_woken = AtomicBool::new(false);
+        let host_eventfd = current!().host_eventfd().clone();
+        Self {
+            is_woken,
+            host_eventfd,
+        }
+    }
+
+    pub fn is_woken(&self) -> bool {
+        self.is_woken.load(Ordering::SeqCst)
+    }
+
+    pub fn reset(&self) {
+        self.is_woken.store(false, Ordering::SeqCst);
+    }
+
+    pub fn wait(&self, timeout: Option<&Duration>) -> Result<()> {
+        while !self.is_woken() {
+            self.host_eventfd.poll(timeout)?;
+        }
+        Ok(())
+    }
+
+    pub fn wait_mut(&self, timeout: Option<&mut Duration>) -> Result<()> {
+        let mut remain = timeout.as_ref().map(|d| **d);
+
+        // Need to change timeout from `Option<&mut Duration>` to `&mut Option<Duration>`
+        // so that the Rust compiler is happy about using the variable in a loop.
+        let ret = self.do_wait_mut(&mut remain);
+
+        if let Some(timeout) = timeout {
+            *timeout = remain.unwrap();
+        }
+        ret
+    }
+
+    fn do_wait_mut(&self, remain: &mut Option<Duration>) -> Result<()> {
+        while !self.is_woken() {
+            self.host_eventfd.poll_mut(remain.as_mut())?;
+        }
+        Ok(())
+    }
+
+    pub fn wake(&self) {
+        if self
+            .is_woken
+            .compare_and_swap(false, true, Ordering::SeqCst)
+            == false
+        {
+            self.host_eventfd.write_u64(1);
+        }
+    }
+
+    pub fn batch_wake<'a, I: Iterator<Item = &'a Waker>>(iter: I) {
+        let host_eventfds = iter
+            .filter_map(|waker| waker.inner.upgrade())
+            .filter(|inner| {
+                inner
+                    .is_woken
+                    .compare_and_swap(false, true, Ordering::SeqCst)
+                    == false
+            })
+            .map(|inner| inner.host_eventfd.host_fd())
+            .collect::<Vec<FileDesc>>();
+        unsafe {
+            HostEventFd::write_u64_raw_and_batch(&host_eventfds, 1);
+        }
+    }
+}
diff --git a/src/libos/src/events/waiter_queue.rs b/src/libos/src/events/waiter_queue.rs
new file mode 100644
index 00000000..7ec178e8
--- /dev/null
+++ b/src/libos/src/events/waiter_queue.rs
@@ -0,0 +1,76 @@
+use std::collections::VecDeque;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::time::Duration;
+
+use super::{Waiter, Waker};
+use crate::prelude::*;
+
+/// A queue for waiters.
+///
+/// By using this queue, we can wake up threads in their waiters' enqueue order.
+///
+/// While the queue is conceptually for `Waiter`s, it internally maintains a list
+/// of `Waker`s.
+pub struct WaiterQueue {
+    count: AtomicUsize,
+    wakers: SgxMutex<VecDeque<Waker>>,
+}
+
+impl WaiterQueue {
+    /// Creates an empty queue for `Waiter`s.
+    pub fn new() -> Self {
+        Self {
+            count: AtomicUsize::new(0),
+            wakers: SgxMutex::new(VecDeque::new()),
+        }
+    }
+
+    /// Returns whether the queue is empty.
+    pub fn is_empty(&self) -> bool {
+        self.count.load(Ordering::SeqCst) == 0
+    }
+
+    /// Reset a waiter and enqueue it.
+    ///
+    /// It is allowed to enqueue a waiter more than once before it is dequeued.
+    /// But this is usually not a good idea. It is the callers' responsibility
+    /// to use the API properly.
+    pub fn reset_and_enqueue(&self, waiter: &Waiter) {
+        waiter.reset();
+
+        let mut wakers = self.wakers.lock().unwrap();
+        self.count.fetch_add(1, Ordering::SeqCst);
+        wakers.push_back(waiter.waker());
+    }
+
+    /// Dequeue a waiter and wake up its thread.
+    pub fn dequeue_and_wake_one(&self) -> usize {
+        self.dequeue_and_wake_nr(1)
+    }
+
+    /// Dequeue all waiters and wake up their threads.
+    pub fn dequeue_and_wake_all(&self) -> usize {
+        self.dequeue_and_wake_nr(usize::MAX)
+    }
+
+    /// Deuque a maximum numer of waiters and wake up their threads.
+    pub fn dequeue_and_wake_nr(&self, max_count: usize) -> usize {
+        // The quick path for a common case
+        if self.is_empty() {
+            return 0;
+        }
+
+        // Dequeue wakers
+        let to_wake = {
+            let mut wakers = self.wakers.lock().unwrap();
+            let max_count = max_count.min(wakers.len());
+            let to_wake: Vec<Waker> = wakers.drain(..max_count).collect();
+            self.count.fetch_sub(to_wake.len(), Ordering::SeqCst);
+            to_wake
+        };
+
+        // Wake in batch
+        Waker::batch_wake(to_wake.iter());
+        to_wake.len()
+    }
+}
diff --git a/src/libos/src/events/waiter_queue_observer.rs b/src/libos/src/events/waiter_queue_observer.rs
new file mode 100644
index 00000000..fe7ed930
--- /dev/null
+++ b/src/libos/src/events/waiter_queue_observer.rs
@@ -0,0 +1,35 @@
+use std::any::Any;
+use std::marker::PhantomData;
+
+use super::{Event, Observer, WaiterQueue};
+use crate::prelude::*;
+
+/// A Observer associated with a WaiterQueue.
+///
+/// Once the observer receives any interesting events, it will dequeue and
+/// wake up all `Waiters` in the associated `WaiterQueue`.
+pub struct WaiterQueueObserver<E: Event> {
+    waiter_queue: WaiterQueue,
+    phantom: PhantomData<E>,
+}
+
+impl<E: Event> WaiterQueueObserver<E> {
+    pub fn new() -> Arc<Self> {
+        let waiter_queue = WaiterQueue::new();
+        let phantom = PhantomData;
+        Arc::new(Self {
+            waiter_queue,
+            phantom,
+        })
+    }
+
+    pub fn waiter_queue(&self) -> &WaiterQueue {
+        &self.waiter_queue
+    }
+}
+
+impl<E: Event> Observer<E> for WaiterQueueObserver<E> {
+    fn on_event(&self, event: &E, _metadata: &Option<Box<dyn Any + Send + Sync>>) {
+        self.waiter_queue.dequeue_and_wake_all();
+    }
+}
diff --git a/src/libos/src/lib.rs b/src/libos/src/lib.rs
index 8e98315c..40f9e137 100644
--- a/src/libos/src/lib.rs
+++ b/src/libos/src/lib.rs
@@ -62,6 +62,7 @@ mod error;
 
 mod config;
 mod entry;
+mod events;
 mod exception;
 mod fs;
 mod interrupt;
diff --git a/src/libos/src/process/thread/builder.rs b/src/libos/src/process/thread/builder.rs
index 90544687..ee66feb8 100644
--- a/src/libos/src/process/thread/builder.rs
+++ b/src/libos/src/process/thread/builder.rs
@@ -4,6 +4,7 @@ use super::{
     FileTableRef, FsViewRef, ProcessRef, ProcessVM, ProcessVMRef, ResourceLimitsRef, SchedAgentRef,
     SigQueues, SigSet, Task, Thread, ThreadId, ThreadInner, ThreadName, ThreadRef,
 };
+use crate::events::HostEventFd;
 use crate::prelude::*;
 use crate::time::ThreadProfiler;
 
@@ -116,6 +117,7 @@ impl ThreadBuilder {
         } else {
             SgxMutex::new(None)
         };
+        let host_eventfd = Arc::new(HostEventFd::new()?);
 
         let new_thread = Arc::new(Thread {
             task,
@@ -134,6 +136,7 @@ impl ThreadBuilder {
             sig_tmp_mask,
             sig_stack,
             profiler,
+            host_eventfd,
         });
 
         let mut inner = new_thread.process().inner();
diff --git a/src/libos/src/process/thread/mod.rs b/src/libos/src/process/thread/mod.rs
index f51a2ebf..ed41f337 100644
--- a/src/libos/src/process/thread/mod.rs
+++ b/src/libos/src/process/thread/mod.rs
@@ -6,6 +6,7 @@ use super::{
     FileTableRef, ForcedExitStatus, FsViewRef, ProcessRef, ProcessVM, ProcessVMRef,
     ResourceLimitsRef, SchedAgentRef, TermStatus, ThreadRef,
 };
+use crate::events::HostEventFd;
 use crate::fs::{EventCreationFlags, EventFile};
 use crate::net::THREAD_NOTIFIERS;
 use crate::prelude::*;
@@ -44,6 +45,8 @@ pub struct Thread {
     sig_stack: SgxMutex<Option<SigStack>>,
     // System call timing
     profiler: SgxMutex<Option<ThreadProfiler>>,
+    // Misc
+    host_eventfd: Arc<HostEventFd>,
 }
 
 #[derive(Debug, PartialEq, Clone, Copy)]
@@ -144,6 +147,10 @@ impl Thread {
         *self.name.write().unwrap() = new_name;
     }
 
+    pub fn host_eventfd(&self) -> &Arc<HostEventFd> {
+        &self.host_eventfd
+    }
+
     pub(super) fn start(&self, host_tid: pid_t) {
         self.sched().lock().unwrap().attach(host_tid);
         self.inner().start();
diff --git a/src/libos/src/time/mod.rs b/src/libos/src/time/mod.rs
index 454c42c6..631ddaeb 100644
--- a/src/libos/src/time/mod.rs
+++ b/src/libos/src/time/mod.rs
@@ -13,6 +13,7 @@ pub mod timer_slack;
 pub mod up_time;
 
 pub use profiler::ThreadProfiler;
+pub use timer_slack::TIMERSLACK;
 
 #[allow(non_camel_case_types)]
 pub type time_t = i64;
@@ -73,6 +74,15 @@ pub struct timespec_t {
     nsec: i64,
 }
 
+impl From<Duration> for timespec_t {
+    fn from(duration: Duration) -> timespec_t {
+        let sec = duration.as_secs() as time_t;
+        let nsec = duration.subsec_nanos() as i64;
+        debug_assert!(sec >= 0); // nsec >= 0 always holds
+        timespec_t { sec, nsec }
+    }
+}
+
 impl timespec_t {
     pub fn from_raw_ptr(ptr: *const timespec_t) -> Result<timespec_t> {
         let ts = unsafe { *ptr };
diff --git a/src/pal/src/ocalls/event.c b/src/pal/src/ocalls/event.c
new file mode 100644
index 00000000..edeb725c
--- /dev/null
+++ b/src/pal/src/ocalls/event.c
@@ -0,0 +1,43 @@
+#define _GNU_SOURCE
+#include "ocalls.h"
+#include <errno.h>
+#include <signal.h>
+#include <poll.h>
+#include <unistd.h>
+#include <sys/eventfd.h>
+
+int occlum_ocall_eventfd(unsigned int initval, int flags) {
+    return eventfd(initval, flags);
+}
+
+int occlum_ocall_eventfd_poll(int eventfd, struct timespec *timeout) {
+    int ret;
+
+    struct pollfd pollfds[1];
+    pollfds[0].fd = eventfd;
+    pollfds[0].events = POLLIN;
+    pollfds[0].revents = 0;
+
+    // We use the ppoll syscall directly instead of the libc wrapper. This
+    // is because the syscall version updates the timeout argument to indicate
+    // how much time was left (which what we want), while the libc wrapper
+    // keeps the timeout argument unchanged.
+    ret = raw_ppoll(pollfds, 1, timeout);
+    if (ret < 0) {
+        return -1;
+    }
+
+    char buf[8];
+    read(eventfd, buf, 8);
+    return 0;
+}
+
+void occlum_ocall_eventfd_write_batch(
+    int *eventfds,
+    size_t num_fds,
+    uint64_t val
+) {
+    for (int fd_i = 0; fd_i < num_fds; fd_i++) {
+        write(eventfds[fd_i], &val, sizeof(val));
+    }
+}
diff --git a/src/pal/src/ocalls/fs.c b/src/pal/src/ocalls/fs.c
index ce6613d8..7b7ccf6d 100644
--- a/src/pal/src/ocalls/fs.c
+++ b/src/pal/src/ocalls/fs.c
@@ -2,17 +2,12 @@
 #include <errno.h>
 #include <net/if.h>
 #include <unistd.h>
-#include <sys/eventfd.h>
 #include <sys/ioctl.h>
 
 void occlum_ocall_sync(void) {
     sync();
 }
 
-int occlum_ocall_eventfd(unsigned int initval, int flags) {
-    return eventfd(initval, flags);
-}
-
 int occlum_ocall_ioctl_repack(int fd, int request, char *buf, int len, int *recv_len) {
     int ret = 0;
 
diff --git a/src/pal/src/pal_syscall.h b/src/pal/src/pal_syscall.h
index 13aa145b..5fe586e8 100644
--- a/src/pal/src/pal_syscall.h
+++ b/src/pal/src/pal_syscall.h
@@ -12,5 +12,6 @@
 #define tgkill(tgid, tid, signum)       ((int)syscall(__NR_tgkill, (tgid), (tid), (signum)));
 #define futex_wait(addr, val, timeout)  ((int)syscall(__NR_futex, (addr), FUTEX_WAIT, (val), (timeout)))
 #define futex_wake(addr)                ((int)syscall(__NR_futex, (addr), FUTEX_WAKE, 1))
+#define raw_ppoll(fds, nfds, timeout)   ((int)syscall(__NR_ppoll, (fds), (nfds), (timeout), NULL, 0))
 
 #endif /* __PAL_SYSCALL_H__ */