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Merged
dlunch merged 2 commits into from
Apr 5, 2026
Merged

Add Jvm object monitor and remove rust_object_field from Object/Thread #138

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52b328e
Add object monitor to Jvm with object_wait, object_listen and object_…
dlunch Apr 5, 2026
70c6193
Replace rust_object_field events with Jvm monitor in Object and Thread
dlunch Apr 5, 2026
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2 changes: 1 addition & 1 deletion Cargo.lock
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1 change: 0 additions & 1 deletion java_runtime/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ tracing = { workspace = true }

chrono = { version = "^0.4", default-features = false }
encoding_rs = { version = "^0.8", features = ["alloc"], default-features = false }
event-listener = { version = "^5.4", default-features = false }
zip = { version = "^6.0", features = ["deflate"], default-features = false }
url = { version = "^2.5", default-features = false }

Expand Down
47 changes: 16 additions & 31 deletions java_runtime/src/classes/java/lang/object.rs
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Original file line number Diff line number Diff line change
@@ -1,13 +1,12 @@
use core::{hash::BuildHasher, time::Duration};

use alloc::{boxed::Box, format, sync::Arc, vec};
use alloc::{boxed::Box, format, vec};

use dyn_clone::clone_box;
use event_listener::Event;
use hashbrown::DefaultHashBuilder;
use java_class_proto::{JavaFieldProto, JavaMethodProto};
use java_class_proto::JavaMethodProto;
use java_constants::MethodAccessFlags;
use jvm::{Array, ClassInstance, ClassInstanceRef, Jvm, Result, runtime::JavaLangString};
use jvm::{ClassInstance, ClassInstanceRef, Jvm, Result, runtime::JavaLangString};

use crate::{Runtime, RuntimeClassProto, RuntimeContext, SpawnCallback, classes::java::lang::String};

Expand All @@ -34,7 +33,7 @@ impl Object {
JavaMethodProto::new("wait", "()V", Self::wait, Default::default()),
JavaMethodProto::new("finalize", "()V", Self::finalize, Default::default()),
],
fields: vec![JavaFieldProto::new("waitEvent", "[B", Default::default())],
fields: vec![],
access_flags: Default::default(),
}
}
Expand Down Expand Up @@ -107,27 +106,15 @@ impl Object {
async fn notify(jvm: &Jvm, _: &mut RuntimeContext, this: ClassInstanceRef<Self>) -> Result<()> {
tracing::debug!("java.lang.Object::notify({:?})", &this);

let wait_event: ClassInstanceRef<Array<i8>> = jvm.get_field(&this, "waitEvent", "[B").await?;
if wait_event.is_null() {
return Ok(());
}

let wait_event: Arc<Event> = jvm.get_rust_object_field(&this, "waitEvent").await?;
wait_event.notify(1);
jvm.object_notify(&this, 1);

Ok(())
}

async fn notify_all(jvm: &Jvm, _: &mut RuntimeContext, this: ClassInstanceRef<Self>) -> Result<()> {
tracing::debug!("java.lang.Object::notifyAll({:?})", &this);

let wait_event: ClassInstanceRef<Array<i8>> = jvm.get_field(&this, "waitEvent", "[B").await?;
if wait_event.is_null() {
return Ok(());
}

let wait_event: Arc<Event> = jvm.get_rust_object_field(&this, "waitEvent").await?;
wait_event.notify(usize::MAX);
jvm.object_notify(&this, usize::MAX);

Ok(())
}
Expand All @@ -140,24 +127,21 @@ impl Object {
Ok(())
}

async fn wait_long_int(jvm: &Jvm, context: &mut RuntimeContext, mut this: ClassInstanceRef<Self>, millis: i64, nanos: i32) -> Result<()> {
async fn wait_long_int(jvm: &Jvm, context: &mut RuntimeContext, this: ClassInstanceRef<Self>, millis: i64, nanos: i32) -> Result<()> {
tracing::debug!("java.lang.Object::wait({:?}, {:?}, {:?})", &this, millis, nanos);

let wait_event = Arc::new(Event::new());
jvm.put_rust_object_field(&mut this, "waitEvent", wait_event.clone()).await?;

struct Waiter {
struct TimeoutNotifier {
timeout: i64,
wait_event: Arc<Event>,
jvm: Jvm,
this: Box<dyn ClassInstance>,
context: Box<dyn Runtime>,
}

#[async_trait::async_trait]
impl SpawnCallback for Waiter {
impl SpawnCallback for TimeoutNotifier {
async fn call(&self) -> Result<()> {
self.context.sleep(Duration::from_millis(self.timeout as _)).await;

self.wait_event.notify(1); // TODO this would notify other waiter
self.jvm.object_notify(&self.this, 1); // TODO this may wake an unrelated waiter
Ok(())
}
}
Expand All @@ -166,15 +150,16 @@ impl Object {
if timeout != 0 {
context.spawn(
jvm,
Box::new(Waiter {
Box::new(TimeoutNotifier {
timeout,
wait_event: wait_event.clone(),
jvm: jvm.clone(),
this: this.clone().into(),
context: clone_box(context),
}),
);
}

wait_event.listen().await;
jvm.object_wait(&this).await?;

Ok(())
}
Expand Down
45 changes: 19 additions & 26 deletions java_runtime/src/classes/java/lang/thread.rs
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Original file line number Diff line number Diff line change
@@ -1,11 +1,9 @@
use alloc::{boxed::Box, sync::Arc, vec};
use alloc::{boxed::Box, vec};
use core::time::Duration;

use event_listener::Event;

use java_class_proto::{JavaFieldProto, JavaMethodProto};
use java_constants::MethodAccessFlags;
use jvm::{Array, ClassInstanceRef, Jvm, Result, runtime::JavaLangString};
use jvm::{ClassInstanceRef, Jvm, Result, runtime::JavaLangString};

use crate::{RuntimeClassProto, RuntimeContext, SpawnCallback, classes::java::lang::Runnable};

Expand Down Expand Up @@ -40,7 +38,7 @@ impl Thread {
fields: vec![
JavaFieldProto::new("id", "J", Default::default()),
JavaFieldProto::new("target", "Ljava/lang/Runnable;", Default::default()),
JavaFieldProto::new("joinEvent", "[B", Default::default()),
JavaFieldProto::new("alive", "Z", Default::default()),
],
access_flags: Default::default(),
}
Expand Down Expand Up @@ -84,7 +82,6 @@ impl Thread {
struct ThreadStartProxy {
jvm: Jvm,
thread_id: i32,
join_event: Arc<Event>,
this: ClassInstanceRef<Thread>,
}

Expand Down Expand Up @@ -129,14 +126,15 @@ impl Thread {

self.jvm.detach_thread()?;

self.join_event.notify(usize::MAX);
let mut this = self.this.clone();
self.jvm.put_field(&mut this, "alive", "Z", false).await.unwrap();
self.jvm.object_notify(&self.this, usize::MAX);

Ok(())
}
}

let join_event = Arc::new(Event::new());
jvm.put_rust_object_field(&mut this, "joinEvent", join_event.clone()).await?;
jvm.put_field(&mut this, "alive", "Z", true).await?;

let id: i32 = jvm.invoke_virtual(&this, "hashCode", "()I", ()).await?;

Expand All @@ -145,7 +143,6 @@ impl Thread {
Box::new(ThreadStartProxy {
jvm: jvm.clone(),
thread_id: id,
join_event,
this: this.clone(),
}),
);
Expand All @@ -164,27 +161,23 @@ impl Thread {
Ok(())
}

async fn join(jvm: &Jvm, _context: &mut RuntimeContext, mut this: ClassInstanceRef<Self>) -> Result<()> {
async fn join(jvm: &Jvm, _context: &mut RuntimeContext, this: ClassInstanceRef<Self>) -> Result<()> {
tracing::debug!("java.lang.Thread::join({:?})", &this);

// TODO we don't have get same field twice
let raw_join_event: ClassInstanceRef<Array<i8>> = jvm.get_field(&this, "joinEvent", "[B").await?;
if raw_join_event.is_null() {
return Ok(()); // already joined or not started
loop {
let listener = jvm.object_listen(&this);
let alive: bool = jvm.get_field(&this, "alive", "Z").await?;
if !alive {
return Ok(());
}
listener.await;
}

let join_event: Arc<Event> = jvm.get_rust_object_field(&this, "joinEvent").await?;
join_event.listen().await;

jvm.put_field(&mut this, "joinEvent", "[B", None).await?;

Ok(())
}

async fn is_alive(_jvm: &Jvm, _: &mut RuntimeContext, this: ClassInstanceRef<Self>) -> Result<bool> {
tracing::warn!("stub java.lang.Thread::isAlive({:?})", &this);

Ok(true)
async fn is_alive(jvm: &Jvm, _: &mut RuntimeContext, this: ClassInstanceRef<Self>) -> Result<bool> {
tracing::debug!("java.lang.Thread::isAlive({:?})", &this);
let alive: bool = jvm.get_field(&this, "alive", "Z").await?;
Ok(alive)
}

async fn sleep(_: &Jvm, context: &mut RuntimeContext, duration: i64) -> Result<()> {
Expand Down
2 changes: 2 additions & 0 deletions jvm/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@ nom = { workspace = true }
parking_lot = { workspace = true }
tracing = { workspace = true }

event-listener = { version = "^5.4", default-features = false }

java_constants = { workspace = true }

[dev-dependencies]
Expand Down
36 changes: 35 additions & 1 deletion jvm/src/jvm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,14 +3,16 @@
use alloc::{borrow::ToOwned, boxed::Box, collections::BTreeMap, format, string::String, sync::Arc, vec::Vec};
use core::{
fmt::Debug,
hash::BuildHasher,
iter,
mem::{forget, size_of_val},
sync::atomic::{AtomicBool, Ordering},
};

use bytemuck::cast_slice;
use dyn_clone::clone_box;
use hashbrown::HashSet;
use event_listener::{Event, EventListener};
use hashbrown::{DefaultHashBuilder, HashSet};
use parking_lot::RwLock;

use java_constants::{ClassAccessFlags, MethodAccessFlags};
Expand All @@ -36,6 +38,8 @@ struct JvmInner {
classes: RwLock<BTreeMap<String, Class>>,
threads: RwLock<BTreeMap<u64, JvmThread>>,
all_objects: RwLock<HashSet<Box<dyn ClassInstance>>>,
monitors: RwLock<BTreeMap<u64, Arc<Event>>>,
monitor_hasher: DefaultHashBuilder,
get_current_thread_id: Box<dyn Fn() -> u64 + Sync + Send>,
bootstrap_class_loader: Box<dyn BootstrapClassLoader>,
bootstrapping: AtomicBool,
Expand All @@ -57,6 +61,8 @@ impl Jvm {
classes: RwLock::new(BTreeMap::new()),
threads: RwLock::new(BTreeMap::new()),
all_objects: RwLock::new(HashSet::new()),
monitors: RwLock::new(BTreeMap::new()),
monitor_hasher: DefaultHashBuilder::default(),
get_current_thread_id: Box::new(get_current_thread_id),
bootstrap_class_loader: Box::new(bootstrap_class_loader),
bootstrapping: AtomicBool::new(true),
Expand Down Expand Up @@ -464,6 +470,21 @@ impl Jvm {
self.inner.classes.read().get(class_name).cloned()
}

pub fn object_listen(&self, obj: &Box<dyn ClassInstance>) -> EventListener {
self.get_or_create_monitor(obj).listen()
}

pub async fn object_wait(&self, obj: &Box<dyn ClassInstance>) -> Result<()> {
self.object_listen(obj).await;

Ok(())
}

pub fn object_notify(&self, obj: &Box<dyn ClassInstance>, count: usize) {
let monitor = self.get_or_create_monitor(obj);
monitor.notify(count);
}

#[async_recursion::async_recursion]
pub async fn resolve_class(&self, class_name: &str) -> Result<Class> {
self.resolve_class_internal(class_name, None).await
Expand Down Expand Up @@ -720,6 +741,19 @@ impl Jvm {
}
}

fn get_or_create_monitor(&self, obj: &Box<dyn ClassInstance>) -> Arc<Event> {
let key = self.inner.monitor_hasher.hash_one(obj);

let monitors = self.inner.monitors.read();
if let Some(monitor) = monitors.get(&key) {
return monitor.clone();
}
drop(monitors);

let mut monitors = self.inner.monitors.write();
monitors.entry(key).or_insert_with(|| Arc::new(Event::new())).clone()
}

pub(crate) fn find_field(&self, class: &dyn ClassDefinition, name: &str, descriptor: &str) -> Result<Option<Box<dyn Field>>> {
let field = class.field(name, descriptor, false);

Expand Down
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