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fix(pd): guard remote_agents dict with a lock to fix NIXL concurrent-add race (GH-1470) #1505

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fix(pd): guard remote_agents dict with a lock to fix NIXL concurrent-add race (GH-1470) #1505

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47 changes: 27 additions & 20 deletions lightllm/server/router/model_infer/mode_backend/pd/nixl_kv_transporter.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
import pickle
import copy
import os
import threading
import time
from dataclasses import dataclass
from typing import Dict
Expand Down Expand Up @@ -40,6 +41,10 @@ def __init__(self, node_id: int, tp_idx: int, kv_move_buffer: Tensor):
self.nixl_agent = NixlWrapper(self.agent_name, conf)
self._register_kv_move_buffer(kv_move_buffer=kv_move_buffer)
self.remote_agents: Dict[str, PDAgentMetadata] = {}
# remote_agents is read and mutated from several worker threads (recv, dispatch,
# accept_peer, request/ready page loops, ...), so every access needs to go through
# this lock to avoid concurrent add/remove races on the same peer (see GH-1470).
self._remote_agents_lock = threading.Lock()
return

@property
Expand Down Expand Up @@ -73,36 +78,38 @@ def _create_paged_xfer_handles(self, reg_desc: "nixlBind.nixlRegDList", page_num
return self.nixl_agent.prep_xfer_dlist(agent_name, descs, "VRAM")

def connect_add_remote_agent(self, remote_agent: PDAgentMetadata):
if remote_agent.agent_name in self.remote_agents:
return
with self._remote_agents_lock:
if remote_agent.agent_name in self.remote_agents:
return

start_time = time.time()
start_time = time.time()

peer_name = self.nixl_agent.add_remote_agent(remote_agent.agent_metadata)
if isinstance(peer_name, bytes):
peer_name = peer_name.decode()
peer_name = self.nixl_agent.add_remote_agent(remote_agent.agent_metadata)
if isinstance(peer_name, bytes):
peer_name = peer_name.decode()

assert (
peer_name == remote_agent.agent_name
), f"Peer name {peer_name} does not match remote name {remote_agent.agent_name}"
assert (
peer_name == remote_agent.agent_name
), f"Peer name {peer_name} does not match remote name {remote_agent.agent_name}"

page_mem_desc = self.nixl_agent.deserialize_descs(remote_agent.page_reg_desc)
kv_page_xfer_handles = self._create_paged_xfer_handles(
page_mem_desc, remote_agent.num_pages, agent_name=peer_name
)
remote_agent.page_xfer_handles = kv_page_xfer_handles
page_mem_desc = self.nixl_agent.deserialize_descs(remote_agent.page_reg_desc)
kv_page_xfer_handles = self._create_paged_xfer_handles(
page_mem_desc, remote_agent.num_pages, agent_name=peer_name
)
remote_agent.page_xfer_handles = kv_page_xfer_handles

logger.info(
f"Added remote agent {peer_name} with mem desc {page_mem_desc} cost time: {time.time() - start_time} s"
)
logger.info(
f"Added remote agent {peer_name} with mem desc {page_mem_desc} cost time: {time.time() - start_time} s"
)

self.remote_agents[remote_agent.agent_name] = remote_agent
self.remote_agents[remote_agent.agent_name] = remote_agent
return

def remove_remote_agent(self, peer_name: str):
if peer_name in self.remote_agents:
with self._remote_agents_lock:
remote_agent: PDAgentMetadata = self.remote_agents.pop(peer_name, None)
if remote_agent is not None:
try:
remote_agent: PDAgentMetadata = self.remote_agents.pop(peer_name, None)
assert remote_agent.agent_name == peer_name
self.nixl_agent.remove_remote_agent(remote_agent.agent_name)
if remote_agent.page_xfer_handles is not None:
Expand Down