fix double acquire attempt for m_pool_lock

misc/aliases

@@ -49,7 +49,9 @@ case "$1" in
  source misc/git/pre-commit
  virtualize_libmc "`which python-dbg || which python3-dbg`"
  python setup.py build_ext --inplace
- if [ -n "$2" ]; then
+ if [ "$2" == "bench" ]; then
+ cygdb . -- -ex start --args python misc/runbench.py
+ elif [ -n "$2" ]; then
  pattern="$2"
  shift 2
  cmds=(-ex start)

src/ClientPool.cpp

@@ -50,6 +50,7 @@ int ClientPool::init(const char* const * hosts, const uint32_t* ports,
  const size_t n, const char* const * aliases) {
  updateServers(hosts, ports, n, aliases);
  std::unique_lock initializing(m_acquiring_growth);
+ std::lock_guard config_pool(m_pool_lock);
  return growPool(m_initial_clients);
 }
 
@@ -86,10 +87,9 @@ int ClientPool::setup(Client* c) {
  return c->init(m_hosts.data(), m_ports.data(), m_hosts.size(), m_aliases.data());
 }
 
-// if called outside acquire, needs to own m_acquiring_growth
+// needs to hold both m_acquiring_growth and m_pool_lock
 int ClientPool::growPool(size_t by) {
  assert(by > 0);
- std::lock_guard growing_pool(m_pool_lock);
  size_t from = m_clients.size();
  m_clients.resize(from + by);
  std::atomic<int> rv = 0;
@@ -115,6 +115,7 @@ inline bool ClientPool::shouldGrowUnsafe() {
 int ClientPool::autoGrow() {
  std::unique_lock<std::shared_mutex> growing(m_acquiring_growth);
  if (shouldGrowUnsafe()) {
+ std::lock_guard growing_pool(m_pool_lock);
  return growPool(MIN(m_max_clients - m_clients.size(),
  MIN(m_max_growth, m_clients.size())));
  }