/* Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2.0, as published by the Free Software Foundation. This program is also distributed with certain software (including but not limited to OpenSSL) that is licensed under separate terms, as designated in a particular file or component or in included license documentation. The authors of MySQL hereby grant you an additional permission to link the program and your derivative works with the separately licensed software that they have included with MySQL. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0, for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ /** @file mysys/win_timers.cc */ #if defined(_WIN32) #include #include /* Timer Queue and IO completion port functions */ #include "my_dbug.h" #include "my_sys.h" /* my_message_local */ #include "my_thread.h" /* my_thread_init, my_thread_end */ #include "my_timer.h" /* my_timer_t */ #include "mysql/psi/mysql_thread.h" #include "mysys_err.h" #include "mysys_priv.h" /* key_thread_timer_notifier */ enum enum_timer_state { TIMER_SET = false, TIMER_EXPIRED = true }; // Timer notifier thread id. static my_thread_handle timer_notify_thread; // IO completion port handle HANDLE io_compl_port = 0; // Timer queue handle HANDLE timer_queue = 0; /** Callback function registered to execute on timer expiration. @param timer_data timer data passed to function. @param timer_or_wait_fired flag to represent timer fired or signalled. @remark this function is executed in timer owner thread when timer expires. */ static void CALLBACK timer_callback_function( PVOID timer_data, BOOLEAN timer_or_wait_fired MY_ATTRIBUTE((unused))) { my_timer_t *timer = (my_timer_t *)timer_data; DBUG_ASSERT(timer != NULL); timer->id.timer_state = TIMER_EXPIRED; PostQueuedCompletionStatus(io_compl_port, 0, (ULONG_PTR)timer, 0); } /** Timer expiration notification thread. @param arg Unused. */ static void *timer_notify_thread_func(void *arg MY_ATTRIBUTE((unused))) { DWORD bytes_transferred; ULONG_PTR compl_key; LPOVERLAPPED overlapped; my_timer_t *timer; my_thread_init(); while (1) { // Get IO Completion status. if (GetQueuedCompletionStatus(io_compl_port, &bytes_transferred, &compl_key, &overlapped, INFINITE) == 0) break; timer = (my_timer_t *)compl_key; timer->notify_function(timer); } my_thread_end(); return NULL; } /** Delete a timer. @param timer Timer Object. @param state The state of the timer at the time of deletion, either signaled (0) or nonsignaled (1). @return 0 On Success -1 On error. */ static int delete_timer(my_timer_t *timer, int *state) { int ret_val; int retry_count = 3; DBUG_ASSERT(timer != 0); DBUG_ASSERT(timer_queue != 0); if (state != NULL) *state = 0; if (timer->id.timer_handle) { do { ret_val = DeleteTimerQueueTimer(timer_queue, timer->id.timer_handle, NULL); if (ret_val != 0) { /** From MSDN documentation of DeleteTimerQueueTimer: ------------------------------------------------------------------ BOOL WINAPI DeleteTimerQueueTimer( _In_opt_ HANDLE TimerQueue, _In_ HANDLE Timer, _In_opt_ HANDLE CompletionEvent ); ... If there are outstanding callback functions and CompletionEvent is NULL, the function will fail and set the error code to ERROR_IO_PENDING. This indicates that there are outstanding callback functions. Those callbacks either will execute or are in the middle of executing. ... ------------------------------------------------------------------ So we are here only in 2 cases, 1 When timer is *not* expired yet. 2 When timer is expired and callback function execution is completed. So here in case 1 timer.id->timer_state is TIMER_SET and in case 2 timer.id->timer_state is TIMER_EXPIRED (From MSDN documentation(pasted above), if timer callback function is not yet executed or it is in the middle of execution then DeleteTimerQueueTimer() fails. Hence when we are here, we are sure that state is either TIMER_SET(case 1) or TIMER_EXPIRED(case 2)) Note: timer.id->timer_state is set to TIMER_EXPIRED in timer_callback_function(). This function is executed by the OS thread on timer expiration. On timer expiration, when callback function is in the middle of execution or it is yet to be executed by OS thread the call to DeleteTimerQueueTimer() fails with an error "ERROR_IO_PENDING". In this case, timer.id->timer_state is not accessed in the current code (please check else if block below). Since timer.id->timer_state is not accessed in the current code while it is getting modified in timer_callback_function, no synchronization mechanism used. Setting state to 1(non-signaled) if timer_state is not set to "TIMER_EXPIRED" */ if (timer->id.timer_state != TIMER_EXPIRED && state != NULL) *state = 1; timer->id.timer_handle = 0; } else if (GetLastError() == ERROR_IO_PENDING) { /** Timer is expired and timer callback function execution is not yet completed. Note: timer->id.timer_state is modified in callback function. Accessing timer->id.timer_state here might result in race conditions. Currently we are not accessing timer->id.timer_state here so not using any synchronization mechanism. */ timer->id.timer_handle = 0; ret_val = 1; } else { /** Timer deletion from queue failed and there are no outstanding callback functions for this timer. */ if (--retry_count == 0) { my_message_local(ERROR_LEVEL, EE_FAILED_TO_DELETE_TIMER, errno); return -1; } } } while (ret_val == 0); } return 0; } /** Initialize internal components. @return 0 On success -1 On error. */ int my_timer_initialize(void) { // Create timer queue. timer_queue = CreateTimerQueue(); if (!timer_queue) { my_message_local(ERROR_LEVEL, EE_FAILED_TO_CREATE_TIMER_QUEUE, errno); goto err; } // Create IO completion port. io_compl_port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 0); if (!io_compl_port) { my_message_local(ERROR_LEVEL, EE_FAILED_TO_CREATE_IO_COMPLETION_PORT, errno); goto err; } if (mysql_thread_create(key_thread_timer_notifier, &timer_notify_thread, 0, timer_notify_thread_func, 0)) { my_message_local(ERROR_LEVEL, EE_FAILED_TO_START_TIMER_NOTIFY_THREAD, errno); goto err; } return 0; err: if (timer_queue) { DeleteTimerQueueEx(timer_queue, NULL); timer_queue = 0; } if (io_compl_port) { CloseHandle(io_compl_port); io_compl_port = 0; } return -1; } /** Release any resources that were allocated as part of initialization. */ void my_timer_deinitialize() { if (timer_queue) { DeleteTimerQueueEx(timer_queue, NULL); timer_queue = 0; } if (io_compl_port) { CloseHandle(io_compl_port); io_compl_port = 0; } my_thread_join(&timer_notify_thread, NULL); } /** Create a timer object. @param timer Timer object. @return On success, 0. */ int my_timer_create(my_timer_t *timer) { DBUG_ASSERT(timer_queue != 0); timer->id.timer_handle = 0; return 0; } /** Set the time until the next expiration of the timer. @param timer Timer object. @param time Amount of time (in milliseconds) before the timer expires. @return On success, 0. On error, -1. */ int my_timer_set(my_timer_t *timer, unsigned long time) { DBUG_ASSERT(timer != NULL); DBUG_ASSERT(timer_queue != 0); /** If timer set previously is expired then it will not be removed from the timer queue. Removing it before creating a new timer queue timer. */ if (timer->id.timer_handle != 0) my_timer_delete(timer); timer->id.timer_state = TIMER_SET; if (CreateTimerQueueTimer(&timer->id.timer_handle, timer_queue, timer_callback_function, timer, time, 0, WT_EXECUTEONLYONCE) == 0) return -1; return 0; } /** Cancel the timer. @param timer Timer object. @param state The state of the timer at the time of cancellation, either signaled (0) or nonsignaled (1). @return On success, 0. On error, -1. */ int my_timer_cancel(my_timer_t *timer, int *state) { DBUG_ASSERT(state != NULL); return delete_timer(timer, state); } /** Delete a timer object. @param timer Timer Object. */ void my_timer_delete(my_timer_t *timer) { delete_timer(timer, NULL); } #endif