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Fix P2P Deadlocks #957

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merged 3 commits into from
Jun 23, 2021
Merged

Fix P2P Deadlocks #957

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4703d4e
Do not require that no calls are made post-disconnect_socket
TheBlueMatt Jun 17, 2021
656ed89
No longer block disconnect_socket calls in lightning-net-tokio
TheBlueMatt Jun 17, 2021
05157b1
Clean up docs on peer_handler significantly.
TheBlueMatt Jun 17, 2021
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47 changes: 13 additions & 34 deletions lightning-net-tokio/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,7 @@ use lightning::ln::peer_handler::SocketDescriptor as LnSocketTrait;
use lightning::ln::msgs::{ChannelMessageHandler, RoutingMessageHandler};
use lightning::util::logger::Logger;

use std::{task, thread};
use std::task;
use std::net::SocketAddr;
use std::net::TcpStream as StdTcpStream;
use std::sync::{Arc, Mutex};
Expand Down Expand Up @@ -114,11 +114,6 @@ struct Connection {
// socket. To wake it up (without otherwise changing its state, we can push a value into this
// Sender.
read_waker: mpsc::Sender<()>,
// When we are told by rust-lightning to disconnect, we can't return to rust-lightning until we
// are sure we won't call any more read/write PeerManager functions with the same connection.
// This is set to true if we're in such a condition (with disconnect checked before with the
// top-level mutex held) and false when we can return.
block_disconnect_socket: bool,
read_paused: bool,
rl_requested_disconnect: bool,
id: u64,
Expand Down Expand Up @@ -153,31 +148,24 @@ impl Connection {
} }
}

macro_rules! prepare_read_write_call {
() => { {
let mut us_lock = us.lock().unwrap();
if us_lock.rl_requested_disconnect {
shutdown_socket!("disconnect_socket() call from RL", Disconnect::CloseConnection);
}
us_lock.block_disconnect_socket = true;
} }
}

let read_paused = us.lock().unwrap().read_paused;
let read_paused = {
let us_lock = us.lock().unwrap();
if us_lock.rl_requested_disconnect {
shutdown_socket!("disconnect_socket() call from RL", Disconnect::CloseConnection);
}
us_lock.read_paused
};
tokio::select! {
v = write_avail_receiver.recv() => {
assert!(v.is_some()); // We can't have dropped the sending end, its in the us Arc!
prepare_read_write_call!();
if let Err(e) = peer_manager.write_buffer_space_avail(&mut our_descriptor) {
shutdown_socket!(e, Disconnect::CloseConnection);
}
us.lock().unwrap().block_disconnect_socket = false;
},
_ = read_wake_receiver.recv() => {},
read = reader.read(&mut buf), if !read_paused => match read {
Ok(0) => shutdown_socket!("Connection closed", Disconnect::PeerDisconnected),
Ok(len) => {
prepare_read_write_call!();
let read_res = peer_manager.read_event(&mut our_descriptor, &buf[0..len]);
let mut us_lock = us.lock().unwrap();
match read_res {
Expand All @@ -188,7 +176,6 @@ impl Connection {
},
Err(e) => shutdown_socket!(e, Disconnect::CloseConnection),
}
us_lock.block_disconnect_socket = false;
},
Err(e) => shutdown_socket!(e, Disconnect::PeerDisconnected),
},
Expand Down Expand Up @@ -223,7 +210,7 @@ impl Connection {
(reader, write_receiver, read_receiver,
Arc::new(Mutex::new(Self {
writer: Some(writer), write_avail, read_waker, read_paused: false,
block_disconnect_socket: false, rl_requested_disconnect: false,
rl_requested_disconnect: false,
id: ID_COUNTER.fetch_add(1, Ordering::AcqRel)
})))
}
Expand Down Expand Up @@ -450,18 +437,10 @@ impl peer_handler::SocketDescriptor for SocketDescriptor {
}

fn disconnect_socket(&mut self) {
{
let mut us = self.conn.lock().unwrap();
us.rl_requested_disconnect = true;
us.read_paused = true;
// Wake up the sending thread, assuming it is still alive
let _ = us.write_avail.try_send(());
// Happy-path return:
if !us.block_disconnect_socket { return; }
}
while self.conn.lock().unwrap().block_disconnect_socket {
thread::yield_now();
}
let mut us = self.conn.lock().unwrap();
us.rl_requested_disconnect = true;
// Wake up the sending thread, assuming it is still alive
let _ = us.write_avail.try_send(());
}
}
impl Clone for SocketDescriptor {
Expand Down
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