nushell/crates/nu_plugin_custom_values/src/main.rs
Devyn Cairns c82dfce246
Fix deadlock on PluginCustomValue drop (#12418)
# Description
Because the plugin interface reader thread can be responsible for
sending a drop notification, it's possible for it to end up in a
deadlock where it's waiting for the response to the drop notification
call.

I decided that the best way to address this is to just discard the
response and not wait for it. It's not really important to synchronize
with the response to `Dropped`, so this is probably faster anyway.

cc @ayax79, this is your issue where polars is getting stuck

# User-Facing Changes
- A bug fix
- Custom value plugin: `custom-value handle update` command

# Tests + Formatting

Tried to add a test with a long pipeline with a lot of drops and run it
over and over to reproduce the deadlock.

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`
2024-04-05 21:57:00 -05:00

104 lines
2.7 KiB
Rust

use std::{
collections::BTreeMap,
sync::{atomic::AtomicU64, Mutex},
};
use handle_custom_value::HandleCustomValue;
use nu_plugin::{serve_plugin, EngineInterface, MsgPackSerializer, Plugin, PluginCommand};
mod cool_custom_value;
mod handle_custom_value;
mod second_custom_value;
mod drop_check;
mod generate;
mod generate2;
mod handle_get;
mod handle_make;
mod handle_update;
mod update;
mod update_arg;
use drop_check::{DropCheck, DropCheckValue};
use generate::Generate;
use generate2::Generate2;
use handle_get::HandleGet;
use handle_make::HandleMake;
use handle_update::HandleUpdate;
use nu_protocol::{CustomValue, LabeledError, Spanned, Value};
use update::Update;
use update_arg::UpdateArg;
#[derive(Default)]
pub struct CustomValuePlugin {
counter: AtomicU64,
handles: Mutex<BTreeMap<u64, Value>>,
}
impl CustomValuePlugin {
pub fn new() -> Self {
Self::default()
}
}
impl Plugin for CustomValuePlugin {
fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin = Self>>> {
vec![
Box::new(Generate),
Box::new(Generate2),
Box::new(Update),
Box::new(UpdateArg),
Box::new(DropCheck),
Box::new(HandleGet),
Box::new(HandleMake),
Box::new(HandleUpdate),
]
}
fn custom_value_to_base_value(
&self,
_engine: &EngineInterface,
custom_value: Spanned<Box<dyn CustomValue>>,
) -> Result<Value, LabeledError> {
// HandleCustomValue depends on the plugin state to get.
if let Some(handle) = custom_value
.item
.as_any()
.downcast_ref::<HandleCustomValue>()
{
Ok(self
.handles
.lock()
.map_err(|err| LabeledError::new(err.to_string()))?
.get(&handle.0)
.cloned()
.unwrap_or_else(|| Value::nothing(custom_value.span)))
} else {
custom_value
.item
.to_base_value(custom_value.span)
.map_err(|err| err.into())
}
}
fn custom_value_dropped(
&self,
_engine: &EngineInterface,
custom_value: Box<dyn CustomValue>,
) -> Result<(), LabeledError> {
// This is how we implement our drop behavior.
if let Some(drop_check) = custom_value.as_any().downcast_ref::<DropCheckValue>() {
drop_check.notify();
} else if let Some(handle) = custom_value.as_any().downcast_ref::<HandleCustomValue>() {
if let Ok(mut handles) = self.handles.lock() {
handles.remove(&handle.0);
}
}
Ok(())
}
}
fn main() {
serve_plugin(&CustomValuePlugin::default(), MsgPackSerializer {})
}