From 836abb300ce09b5c5abb7bcd13f04e8c6bd20de3 Mon Sep 17 00:00:00 2001
From: bneradt <bneradt@yahooinc.com>
Date: Thu, 30 Jul 2026 14:31:51 -0500
Subject: [PATCH] Fix JSONRPC server shutdown race

JSONRPC server shutdown can race with worker thread startup. When the
worker starts after stop_thread(), it restores the running flag and
polls a closed socket indefinitely. This causes test_jsonrpcserver and
process shutdown to hang.

This marks the socket server as running before the worker is created,
so a concurrent stop cannot be overwritten. It also passes the owning
server to the worker instead of relying on the mutable global server
pointer.
---
 include/mgmt/rpc/server/IPCSocketServer.h |  2 +-
 src/mgmt/rpc/server/IPCSocketServer.cc    |  6 ++++--
 src/mgmt/rpc/server/RPCServer.cc          | 12 ++++++------
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/include/mgmt/rpc/server/IPCSocketServer.h b/include/mgmt/rpc/server/IPCSocketServer.h
index 4ffe377d43c..7c45204b13f 100644
--- a/include/mgmt/rpc/server/IPCSocketServer.h
+++ b/include/mgmt/rpc/server/IPCSocketServer.h
@@ -144,7 +144,7 @@ class IPCSocketServer : public BaseCommInterface
   void close();
   void late_check_peer_credentials(int peedFd, TSRPCHandlerOptions const &options, swoc::Errata &errata) const;
 
-  std::atomic_bool _running;
+  std::atomic_bool _running{false};
 
   struct sockaddr_un _serverAddr;
   int                _socket{-1};
diff --git a/src/mgmt/rpc/server/IPCSocketServer.cc b/src/mgmt/rpc/server/IPCSocketServer.cc
index e2b235650b0..922db9b8ec3 100644
--- a/src/mgmt/rpc/server/IPCSocketServer.cc
+++ b/src/mgmt/rpc/server/IPCSocketServer.cc
@@ -168,6 +168,10 @@ IPCSocketServer::init()
     return ec;
   }
 
+  // Set this before RPCServer creates the worker thread so an immediate stop
+  // cannot be overwritten when the worker eventually enters run().
+  _running.store(true);
+
   return ec;
 }
 
@@ -201,8 +205,6 @@ IPCSocketServer::poll_for_new_client(std::chrono::milliseconds timeout) const
 void
 IPCSocketServer::run()
 {
-  _running.store(true);
-
   while (_running) {
     // poll till socket it's ready.
     if (!this->poll_for_new_client()) {
diff --git a/src/mgmt/rpc/server/RPCServer.cc b/src/mgmt/rpc/server/RPCServer.cc
index eb121359169..6c8a55afa6a 100644
--- a/src/mgmt/rpc/server/RPCServer.cc
+++ b/src/mgmt/rpc/server/RPCServer.cc
@@ -59,13 +59,13 @@ RPCServer::~RPCServer()
 void * /* static */
 RPCServer::run_thread(void *a)
 {
-  void *ret = a;
-  if (jsonrpcServer->_init) {
-    jsonrpcServer->_rpcThread = jsonrpcServer->_init();
+  auto *server = static_cast<RPCServer *>(a);
+  if (server->_init) {
+    server->_rpcThread = server->_init();
   }
-  jsonrpcServer->_socketImpl->run();
+  server->_socketImpl->run();
   Dbg(dbg_ctl, "Socket stopped");
-  return ret;
+  return a;
 }
 
 void
@@ -75,7 +75,7 @@ RPCServer::start_thread(std::function<TSThread()> const &cb_init, std::function<
   _init    = cb_init;
   _destroy = cb_destroy;
 
-  ink_thread_create(&_this_thread, run_thread, nullptr, 0, 0, nullptr);
+  ink_thread_create(&_this_thread, run_thread, this, 0, 0, nullptr);
 }
 
 void