Initial threadpool implementation for MariaDB 5.5

2025-08-01 03:47:19 +03:00 · 2011-12-08 19:17:49 +01:00
parent 5e7b949e61
commit e91bbca5fb
24 changed files with 2553 additions and 190 deletions
--- a/sql/threadpool_win.cc
+++ b/sql/threadpool_win.cc
@ -0,0 +1,756 @@
+#ifdef _WIN32_WINNT
+#undef _WIN32_WINNT
+#endif
+
+#define _WIN32_WINNT 0x0601
+
+#include <my_global.h>
+#include <violite.h>
+#include <sql_priv.h>
+#include <sql_class.h>
+#include <my_pthread.h>
+#include <scheduler.h>
+#include <sql_connect.h>
+#include <mysqld.h>
+#include <debug_sync.h>
+#include <threadpool.h>
+#include <windows.h>
+
+
+
+TP_STATISTICS tp_stats;
+
+#define WEAK_SYMBOL(return_type, function, ...) \
+  typedef return_type (WINAPI *pFN_##function)(__VA_ARGS__); \
+  static pFN_##function my_##function = (pFN_##function) \
+    (GetProcAddress(GetModuleHandle("kernel32"),#function))
+
+WEAK_SYMBOL(VOID, CancelThreadpoolIo, PTP_IO);
+#define CancelThreadpoolIo my_CancelThreadpoolIo
+
+WEAK_SYMBOL(VOID, CloseThreadpool, PTP_POOL);
+#define CloseThreadpool my_CloseThreadpool
+
+WEAK_SYMBOL(VOID, CloseThreadpoolIo, PTP_IO);
+#define CloseThreadpoolIo my_CloseThreadpoolIo
+
+WEAK_SYMBOL(VOID, CloseThreadpoolTimer,PTP_TIMER);
+#define CloseThreadpoolTimer my_CloseThreadpoolTimer
+
+WEAK_SYMBOL(VOID, CloseThreadpoolWait,PTP_WAIT);
+#define CloseThreadpoolWait my_CloseThreadpoolWait
+
+WEAK_SYMBOL(PTP_POOL, CreateThreadpool,PVOID);
+#define CreateThreadpool my_CreateThreadpool
+
+WEAK_SYMBOL(PTP_IO, CreateThreadpoolIo, HANDLE, PTP_WIN32_IO_CALLBACK, PVOID ,
+  PTP_CALLBACK_ENVIRON);
+#define CreateThreadpoolIo my_CreateThreadpoolIo
+
+WEAK_SYMBOL(PTP_TIMER, CreateThreadpoolTimer, PTP_TIMER_CALLBACK ,
+ PVOID pv, PTP_CALLBACK_ENVIRON pcbe);
+#define CreateThreadpoolTimer my_CreateThreadpoolTimer
+
+WEAK_SYMBOL(PTP_WAIT, CreateThreadpoolWait, PTP_WAIT_CALLBACK, PVOID, 
+  PTP_CALLBACK_ENVIRON);
+#define CreateThreadpoolWait my_CreateThreadpoolWait
+
+WEAK_SYMBOL(VOID, DisassociateCurrentThreadFromCallback, PTP_CALLBACK_INSTANCE);
+#define DisassociateCurrentThreadFromCallback my_DisassociateCurrentThreadFromCallback
+
+WEAK_SYMBOL(DWORD, FlsAlloc, PFLS_CALLBACK_FUNCTION);
+#define FlsAlloc my_FlsAlloc
+
+WEAK_SYMBOL(PVOID, FlsGetValue, DWORD);
+#define FlsGetValue my_FlsGetValue
+
+WEAK_SYMBOL(BOOL, FlsSetValue, DWORD, PVOID);
+#define FlsSetValue my_FlsSetValue
+
+WEAK_SYMBOL(VOID, SetThreadpoolThreadMaximum, PTP_POOL, DWORD);
+#define SetThreadpoolThreadMaximum my_SetThreadpoolThreadMaximum
+
+WEAK_SYMBOL(BOOL, SetThreadpoolThreadMinimum, PTP_POOL, DWORD);
+#define SetThreadpoolThreadMinimum my_SetThreadpoolThreadMinimum
+
+WEAK_SYMBOL(VOID, SetThreadpoolTimer, PTP_TIMER, PFILETIME,DWORD,DWORD);
+#define SetThreadpoolTimer my_SetThreadpoolTimer
+
+WEAK_SYMBOL(VOID, SetThreadpoolWait, PTP_WAIT,HANDLE,PFILETIME);
+#define SetThreadpoolWait my_SetThreadpoolWait
+
+WEAK_SYMBOL(VOID, StartThreadpoolIo, PTP_IO);
+#define StartThreadpoolIo my_StartThreadpoolIo
+
+WEAK_SYMBOL(VOID, WaitForThreadpoolIoCallbacks,PTP_IO, BOOL);
+#define WaitForThreadpoolIoCallbacks my_WaitForThreadpoolIoCallbacks
+
+WEAK_SYMBOL(VOID, WaitForThreadpoolTimerCallbacks, PTP_TIMER, BOOL);
+#define WaitForThreadpoolTimerCallbacks my_WaitForThreadpoolTimerCallbacks
+
+WEAK_SYMBOL(VOID, WaitForThreadpoolWaitCallbacks, PTP_WAIT, BOOL);
+#define WaitForThreadpoolWaitCallbacks my_WaitForThreadpoolWaitCallbacks
+
+WEAK_SYMBOL(BOOL, SetFileCompletionNotificationModes, HANDLE, UCHAR);
+#define SetFileCompletionNotificationModes my_SetFileCompletionNotificationModes
+
+WEAK_SYMBOL(BOOL, TrySubmitThreadpoolCallback, PTP_SIMPLE_CALLBACK pfns, 
+  PVOID pv,PTP_CALLBACK_ENVIRON pcbe);
+#define TrySubmitThreadpoolCallback my_TrySubmitThreadpoolCallback
+
+WEAK_SYMBOL(PTP_WORK, CreateThreadpoolWork, PTP_WORK_CALLBACK pfnwk, PVOID pv,
+  PTP_CALLBACK_ENVIRON pcbe);
+#define CreateThreadpoolWork my_CreateThreadpoolWork
+
+WEAK_SYMBOL(VOID, SubmitThreadpoolWork,PTP_WORK pwk);
+#define SubmitThreadpoolWork my_SubmitThreadpoolWork
+
+WEAK_SYMBOL(VOID, CloseThreadpoolWork, PTP_WORK pwk);
+#define CloseThreadpoolWork my_CloseThreadpoolWork 
+
+#if _MSC_VER >= 1600
+/* Stack size manipulation available only on Win7+ /declarations in VS10 */
+WEAK_SYMBOL(BOOL, SetThreadpoolStackInformation, PTP_POOL, 
+  PTP_POOL_STACK_INFORMATION);
+#define SetThreadpoolStackInformation my_SetThreadpoolStackInformation
+#endif
+
+#if _MSC_VER < 1600
+#define SetThreadpoolCallbackPriority(env,prio)
+typedef enum _TP_CALLBACK_PRIORITY {
+    TP_CALLBACK_PRIORITY_HIGH,
+    TP_CALLBACK_PRIORITY_NORMAL,
+    TP_CALLBACK_PRIORITY_LOW,
+    TP_CALLBACK_PRIORITY_INVALID
+} TP_CALLBACK_PRIORITY;
+#endif
+
+
+/* Log a warning */
+static void tp_log_warning(const char *msg, const char *fct)
+{
+  sql_print_warning("Threadpool: %s. %s failed (last error %d)",msg, fct,
+    GetLastError());
+}
+
+
+PTP_POOL pool;
+DWORD fls;
+extern int skip_net_wait_timeout;
+
+static bool skip_completion_port_on_success = false;
+
+/*
+  Threadpool callbacks.
+
+  io_completion_callback  - handle client request
+  timer_callback - handle wait timeout (kill connection)
+  shm_read_callback, shm_close_callback - shared memory stuff
+  login_callback - user login (submitted as threadpool work)
+
+*/
+
+static void CALLBACK timer_callback(PTP_CALLBACK_INSTANCE instance, 
+  PVOID context, PTP_TIMER timer);
+
+static void CALLBACK io_completion_callback(PTP_CALLBACK_INSTANCE instance, 
+  PVOID context,  PVOID overlapped,  ULONG io_result, ULONG_PTR nbytes, PTP_IO io);
+
+static void CALLBACK shm_read_callback(PTP_CALLBACK_INSTANCE instance,
+  PVOID Context, PTP_WAIT wait,TP_WAIT_RESULT wait_result);
+
+static void CALLBACK shm_close_callback(PTP_CALLBACK_INSTANCE instance,
+  PVOID Context, PTP_WAIT wait,TP_WAIT_RESULT wait_result);
+
+#define CONNECTION_SIGNATURE 0xAFFEAFFE
+
+static void check_thread_init();
+
+/* Get current time as Windows time */
+static ulonglong now()
+{
+  ulonglong current_time;
+  GetSystemTimeAsFileTime((PFILETIME)&current_time);
+  return current_time;
+}
+
+/* 
+  Connection structure, encapsulates THD + structures for asynchronous
+  IO and pool.
+*/
+
+struct connection_t
+{
+  THD *thd;
+  bool logged_in;
+  HANDLE handle;
+  OVERLAPPED overlapped;
+
+  /* absolute time for wait timeout (as Windows time) */
+  volatile ulonglong timeout; 
+
+  PTP_CLEANUP_GROUP cleanup_group;
+  TP_CALLBACK_ENVIRON callback_environ;
+
+  PTP_IO  io;
+  PTP_TIMER timer;
+  PTP_WAIT shm_read;
+};
+
+void init_connection(connection_t *connection)
+{
+  connection->logged_in = false;
+  connection->handle= 0;
+  connection->io= 0;
+  connection->shm_read= 0;
+  connection->timer= 0;
+  connection->logged_in = false;
+  connection->timeout= ULONGLONG_MAX;
+  memset(&connection->overlapped, 0, sizeof(OVERLAPPED));
+  InitializeThreadpoolEnvironment(&connection->callback_environ);
+  SetThreadpoolCallbackPool(&connection->callback_environ, pool);
+  connection->thd = 0;
+}
+
+int init_io(connection_t *connection, THD *thd)
+{
+  connection->thd= thd;
+  Vio *vio = thd->net.vio;
+  switch(vio->type)
+  {
+    case VIO_TYPE_SSL:
+    case VIO_TYPE_TCPIP:
+      connection->handle= (HANDLE)vio->sd;
+      break;
+    case VIO_TYPE_NAMEDPIPE:
+      connection->handle= (HANDLE)vio->hPipe;
+      break;
+    case VIO_TYPE_SHARED_MEMORY:
+      connection->shm_read=  CreateThreadpoolWait(shm_read_callback, connection, 
+        &connection->callback_environ);
+      if (!connection->shm_read)
+      {
+        tp_log_warning("Allocation failed", "CreateThreadpoolWait");
+        return -1;
+      }
+      break;
+    default:
+      abort();
+  }
+
+  if (connection->handle)
+  {
+    /* Performance tweaks (s. MSDN documentation)*/
+    UCHAR flags = FILE_SKIP_SET_EVENT_ON_HANDLE;
+    if (skip_completion_port_on_success)
+    {
+      flags |= FILE_SKIP_COMPLETION_PORT_ON_SUCCESS;
+    }
+    (void)SetFileCompletionNotificationModes(connection->handle, flags);
+
+    /* Assign io completion callback */
+    connection->io = CreateThreadpoolIo(connection->handle, 
+      io_completion_callback, connection, &connection->callback_environ);
+    if(!connection->io)
+    {
+      tp_log_warning("Allocation failed", "CreateThreadpoolWait");
+      return -1;
+    }
+  }
+  connection->timer = CreateThreadpoolTimer(timer_callback, connection, 
+    &connection->callback_environ);
+  if (!connection->timer)
+  {
+    tp_log_warning("Allocation failed", "CreateThreadpoolWait");
+    return -1;
+  }
+
+  return 0;
+}
+
+
+/*
+  Start asynchronous read
+*/
+int start_io(connection_t *connection, PTP_CALLBACK_INSTANCE instance)
+{
+  /* Start async read */
+  DWORD num_bytes = 0;
+  static char c;
+  WSABUF buf;
+  buf.buf= &c;
+  buf.len= 0;
+  DWORD flags=0;
+  DWORD last_error= 0;
+
+  int retval;
+  Vio *vio= connection->thd->net.vio;
+
+  if (vio->type == VIO_TYPE_SHARED_MEMORY)
+  {
+      SetThreadpoolWait(connection->shm_read, vio->event_server_wrote, NULL);
+      return 0;
+  }
+  if (vio->type == VIO_CLOSED)
+  {
+    return -1;
+  }
+
+  DBUG_ASSERT(vio->type == VIO_TYPE_TCPIP || 
+    vio->type == VIO_TYPE_SSL ||
+    vio->type == VIO_TYPE_NAMEDPIPE);
+
+  OVERLAPPED *overlapped= &connection->overlapped;
+  PTP_IO io= connection->io;
+  StartThreadpoolIo(io);
+
+  if (vio->type == VIO_TYPE_TCPIP || vio->type == VIO_TYPE_SSL)
+  {
+    /* Start async io (sockets). */
+    if (WSARecv(vio->sd , &buf, 1, &num_bytes, &flags,
+          overlapped,  NULL) == 0)
+    {
+        retval= last_error= 0;
+    }
+    else
+    {
+      retval= -1;
+      last_error=  WSAGetLastError();
+    }
+  }
+  else
+  {
+    /* Start async io (named pipe) */
+    if (ReadFile(vio->hPipe, &c, 0, &num_bytes ,overlapped))
+    {
+      retval= last_error= 0;
+    }
+    else
+    {
+      retval= -1;
+      last_error= GetLastError();
+    }
+  }
+
+  if (retval == 0 || last_error == ERROR_MORE_DATA)
+  {
+    /*
+      IO successfully finished (synchronously). 
+      If skip_completion_port_on_success is set, we need to handle it right 
+      here, because completion callback would not be executed by the pool.
+    */
+    if(skip_completion_port_on_success)
+    {
+      CancelThreadpoolIo(io);
+      io_completion_callback(instance, connection, overlapped, last_error, 
+        num_bytes, io);
+    }
+    return 0;
+  }
+
+  if(last_error == ERROR_IO_PENDING)
+  {
+    return 0;
+  }
+
+  /* Some error occured */
+  CancelThreadpoolIo(io);
+  return -1;
+}
+
+int login(connection_t *connection, PTP_CALLBACK_INSTANCE instance)
+{
+  if (threadpool_add_connection(connection->thd) == 0
+      && init_io(connection, connection->thd) == 0 
+      && start_io(connection, instance) == 0)
+  {
+    return 0;
+  }
+  return -1;
+}
+
+/*
+  Recalculate wait timeout, maybe reset timer. 
+*/
+void set_wait_timeout(connection_t *connection, ulonglong old_timeout)
+{
+  ulonglong new_timeout = now() + 
+    10000000LL*connection->thd->variables.net_wait_timeout;
+
+  if (new_timeout < old_timeout)
+  {
+    SetThreadpoolTimer(connection->timer, (PFILETIME) &new_timeout, 0, 1000);
+  }
+  connection->timeout = new_timeout;
+}
+
+/*
+  Terminates (idle) connection by closing the socket.
+  This  will activate io_completion_callback() in a different thread
+*/
+void post_kill_notification(connection_t *connection)
+{
+  check_thread_init();
+  THD *thd=connection->thd;
+  mysql_mutex_lock(&thd->LOCK_thd_data);
+  thd->killed = KILL_CONNECTION;
+  vio_shutdown(thd->net.vio, SHUT_RDWR);
+  thd->mysys_var= NULL;
+  mysql_mutex_unlock(&thd->LOCK_thd_data);
+}
+
+
+/* Connection destructor */
+void destroy_connection(connection_t *connection)
+{
+  if (connection->thd)
+  {
+    threadpool_remove_connection(connection->thd);
+  }
+
+  if (connection->io)
+  {
+     WaitForThreadpoolIoCallbacks(connection->io, TRUE); 
+     CloseThreadpoolIo(connection->io);
+  }
+
+  if(connection->shm_read)
+  {
+    WaitForThreadpoolWaitCallbacks(connection->shm_read, TRUE);
+    CloseThreadpoolWait(connection->shm_read);
+  }
+
+  if(connection->timer)
+  {
+    SetThreadpoolTimer(connection->timer, 0, 0, 0);
+    WaitForThreadpoolTimerCallbacks(connection->timer, TRUE);
+    CloseThreadpoolTimer(connection->timer);
+  }
+
+  DestroyThreadpoolEnvironment(&connection->callback_environ);
+}
+
+
+
+/* 
+  This function should be called first whenever a callback is invoked in the 
+  threadpool, does my_thread_init() if not yet done
+*/
+extern ulong thread_created;
+static void check_thread_init()
+{
+  if (FlsGetValue(fls) == NULL)
+  {
+    FlsSetValue(fls, (void *)1);
+    my_thread_init();
+    thread_created++;
+    InterlockedIncrement((volatile long *)&tp_stats.num_worker_threads);
+  }
+}
+
+
+/*
+  Take care of proper cleanup when threadpool threads exit.
+  We do not control how threads are created, thus it is our responsibility to 
+  check that my_thread_init() is called on thread initialization and
+  my_thread_end() on thread destruction. On Windows, FlsAlloc() provides the 
+  thread destruction callbacks.
+*/
+static VOID WINAPI thread_destructor(void *data)
+{
+  if(data)
+  {
+    if (InterlockedDecrement((volatile long *)&tp_stats.num_worker_threads) >= 0)
+    {
+      /*
+        The above check for number of thread >= 0 is due to shutdown code (
+        see tp_end()) where we forcefully set num_worker_threads to 0, even 
+        if not all threads have shut down yet to the point they would ran Fls
+        destructors, even after CloseThreadpool(). See also comment in tp_end().
+      */
+      mysql_mutex_lock(&LOCK_thread_count); 
+      my_thread_end();
+      mysql_mutex_unlock(&LOCK_thread_count); 
+    }
+  }
+}
+
+
+/* Scheduler callback : init */
+bool tp_init(void)
+{
+  fls= FlsAlloc(thread_destructor);
+  pool= CreateThreadpool(NULL);
+  if(!pool)
+  {
+    sql_print_error("Can't create threadpool. "
+      "CreateThreadpool() failed with %d. Likely cause is memory pressure", 
+      GetLastError());
+    exit(1);
+  }
+
+  if (threadpool_max_threads)
+  {
+    SetThreadpoolThreadMaximum(pool,threadpool_max_threads);
+  }
+
+  if (threadpool_min_threads)
+  {
+    if (!SetThreadpoolThreadMinimum(pool, threadpool_min_threads))
+    {
+      tp_log_warning( "Can't set threadpool minimum threads", 
+        "SetThreadpoolThreadMinimum");
+    }
+  }
+
+  /*
+    Control stack size (OS must be Win7 or later, plus corresponding SDK)
+  */
+#if _MSC_VER >=1600
+  if (SetThreadpoolStackInformation)
+  {
+    TP_POOL_STACK_INFORMATION stackinfo;
+    stackinfo.StackCommit = 0;
+    stackinfo.StackReserve = my_thread_stack_size;
+    if (!SetThreadpoolStackInformation(pool, &stackinfo))
+    {
+      tp_log_warning("Can't set threadpool stack size", 
+        "SetThreadpoolStackInformation");
+    }
+  }
+#endif
+
+  skip_net_wait_timeout = 1;
+  return 0;
+}
+
+
+/*
+  Scheduler callback : Destroy the scheduler.
+*/
+
+extern "C" uint  THR_thread_count;
+extern "C" mysql_mutex_t THR_LOCK_threads;
+extern "C" mysql_cond_t THR_COND_threads;
+
+void tp_end(void)
+{
+  if(pool)
+  {
+    SetThreadpoolThreadMaximum(pool, 0);
+    CloseThreadpool(pool);
+
+    /*
+       Tell my_global_thread_end() we're complete.
+
+       This would not be necessary if CloseThreadpool() would synchronously
+       release all threads and wait until they disappear and call all their FLS
+       destrructors . However, threads in the pool are released asynchronously
+       and might spend some time in the CRT shutdown code. Thus zero 
+       num_worker_threads, to avoid thread destructor's my_thread_end()s after 
+       this point.
+    */
+    LONG remaining_threads= 
+      InterlockedExchange( (volatile long *)&tp_stats.num_worker_threads, 0);
+
+    if (remaining_threads)
+    {
+      mysql_mutex_lock(&THR_LOCK_threads);
+      THR_thread_count -= remaining_threads;
+      mysql_cond_signal(&THR_COND_threads);
+      mysql_mutex_unlock(&THR_LOCK_threads);
+    }
+  }
+  skip_net_wait_timeout= 0;
+}
+
+/*
+  Notify pool about connection being killed.
+*/
+void tp_post_kill_notification(THD *thd)
+{
+   if (current_thd == thd)
+    return; /* There is nothing to do.*/
+
+  if (thd->system_thread)
+   return; /* Will crash if we attempt to kill system thread. */
+
+  Vio *vio= thd->net.vio;
+
+  vio_shutdown(vio, SD_BOTH);
+
+}
+
+/*
+  Handle read completion/notification.
+*/
+static VOID CALLBACK io_completion_callback(PTP_CALLBACK_INSTANCE instance, 
+  PVOID context,  PVOID overlapped,  ULONG io_result, ULONG_PTR nbytes, PTP_IO io)
+{
+  if(instance)
+  {
+    check_thread_init();
+  }
+
+  connection_t *connection = (connection_t*)context;
+  THD *thd= connection->thd;
+  ulonglong old_timeout = connection->timeout;
+  connection->timeout = ULONGLONG_MAX;
+
+  if (threadpool_process_request(connection->thd))
+    goto error;
+
+  set_wait_timeout(connection, old_timeout);
+  if(start_io(connection, instance))
+    goto error;
+
+  return;
+
+error:
+  /* Some error has occured. */
+  if (instance)
+    DisassociateCurrentThreadFromCallback(instance);
+
+  destroy_connection(connection);
+  my_free(connection);
+}
+
+
+/* Simple callback for login */
+static void CALLBACK login_callback(PTP_CALLBACK_INSTANCE instance, 
+  PVOID context, PTP_WORK work)
+{
+  if(instance)
+  {
+    check_thread_init();
+  }
+
+  connection_t *connection =(connection_t *)context;
+  if (login(connection, instance) != 0)
+  {
+    destroy_connection(connection);
+    my_free(connection);
+  }
+}
+
+/*
+  Timer callback.
+  Invoked when connection times out (wait_timeout)
+*/
+static VOID CALLBACK timer_callback(PTP_CALLBACK_INSTANCE instance, 
+  PVOID parameter, PTP_TIMER timer)
+{
+  check_thread_init();
+
+  connection_t *con= (connection_t*)parameter;
+  ulonglong timeout= con->timeout;
+
+  if (timeout <= now())
+  {
+    con->thd->killed = KILL_CONNECTION;
+    if(con->thd->net.vio)
+      vio_shutdown(con->thd->net.vio, SD_BOTH);
+  }
+  else if(timeout != ULONGLONG_MAX)
+  {
+    /* 
+      Reset timer. 
+      There is a tiny possibility of a race condition, since the value of timeout 
+      could have changed to smaller value in the thread doing io callback. 
+
+      Given the relative unimportance of the wait timeout, we accept race 
+      condition.
+    */
+    SetThreadpoolTimer(timer, (PFILETIME)&timeout, 0, 1000);
+  }
+}
+
+
+/*
+  Shared memory read callback.
+  Invoked when read event is set on connection.
+*/
+static void CALLBACK shm_read_callback(PTP_CALLBACK_INSTANCE instance,
+  PVOID context, PTP_WAIT wait,TP_WAIT_RESULT wait_result)
+{
+  connection_t *con= (connection_t *)context;
+  /* Disarm wait. */
+  SetThreadpoolWait(wait, NULL, NULL);
+
+  /* 
+    This is an autoreset event, and one wakeup is eaten already by threadpool,
+    and the current state is "not set". Thus we need to reset the event again, 
+    or vio_read will hang.
+  */
+  HANDLE h = con->thd->net.vio->event_server_wrote;
+  SetEvent(h);
+  io_completion_callback(instance, context, NULL, 0, 0 , 0);
+}
+
+
+/*
+  Notify the thread pool about a new connection.
+  NOTE: LOCK_thread_count is locked on entry. This function must unlock it.
+*/
+void tp_add_connection(THD *thd)
+{
+  bool success = false;
+  connection_t *con = (connection_t *)my_malloc(sizeof(connection_t), 0);
+  
+  if (con)
+    threads.append(thd);
+  mysql_mutex_unlock(&LOCK_thread_count);
+
+  if(!con)
+  {
+    tp_log_warning("Allocation failed", "tp_add_connection");
+    return;
+  }
+
+  init_connection(con);
+  con->thd= thd;
+  /* Try to login asynchronously, using threads in the pool */
+  PTP_WORK wrk =  CreateThreadpoolWork(login_callback,con, &con->callback_environ);
+  if (wrk)
+  {
+    SubmitThreadpoolWork(wrk);
+    CloseThreadpoolWork(wrk);
+  }
+  else
+  {
+    /* Likely memory pressure */
+    login_callback(NULL, con, NULL); /* deletes connection if something goes wrong */
+  }
+}
+
+
+
+/*
+  Sets the number of idle threads the thread pool maintains in anticipation of new
+  requests.
+*/
+void tp_set_min_threads(uint val)
+{
+  if (pool)
+    SetThreadpoolThreadMinimum(pool, val);
+}
+
+void tp_set_max_threads(uint val)
+{
+  if (pool)
+    SetThreadpoolThreadMaximum(pool, val);
+}
+
+void tp_wait_begin(THD *thd, int type)
+{
+  if (thd && thd->event_scheduler.data)
+  {
+    /* TODO: call CallbackMayRunLong() */
+  }
+}
+
+void tp_wait_end(THD *thd) 
+{
+  /* Do we need to do anything ? */
+}
+