1/*****************************************************************************
2
3Copyright (c) 2006, 2015, Oracle and/or its affiliates. All Rights Reserved.
4Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
5
6This program is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free Software
8Foundation; version 2 of the License.
9
10This program is distributed in the hope that it will be useful, but WITHOUT
11ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
12FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
13
14You should have received a copy of the GNU General Public License along with
15this program; if not, write to the Free Software Foundation, Inc.,
1651 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
17
18*****************************************************************************/
19
20#include "ut0list.h"
21#include "mem0mem.h"
22#include "ut0wqueue.h"
23
24/*******************************************************************//**
25@file ut/ut0wqueue.cc
26A work queue
27
28Created 4/26/2006 Osku Salerma
29************************************************************************/
30
31/* Work queue. */
32struct ib_wqueue_t {
33 ib_mutex_t mutex; /*!< mutex protecting everything */
34 ib_list_t* items; /*!< work item list */
35 os_event_t event; /*!< event we use to signal additions to list;
36 os_event_set() and os_event_reset() are
37 protected by ib_wqueue_t::mutex */
38};
39
40/****************************************************************//**
41Create a new work queue.
42@return work queue */
43ib_wqueue_t*
44ib_wqueue_create(void)
45/*===================*/
46{
47 ib_wqueue_t* wq = static_cast<ib_wqueue_t*>(
48 ut_malloc_nokey(sizeof(*wq)));
49
50 /* Function ib_wqueue_create() has not been used anywhere,
51 not necessary to instrument this mutex */
52
53 mutex_create(LATCH_ID_WORK_QUEUE, &wq->mutex);
54
55 wq->items = ib_list_create();
56 wq->event = os_event_create(0);
57
58 return(wq);
59}
60
61/****************************************************************//**
62Free a work queue. */
63void
64ib_wqueue_free(
65/*===========*/
66 ib_wqueue_t* wq) /*!< in: work queue */
67{
68 mutex_free(&wq->mutex);
69 ib_list_free(wq->items);
70 os_event_destroy(wq->event);
71
72 ut_free(wq);
73}
74
75/****************************************************************//**
76Add a work item to the queue. */
77void
78ib_wqueue_add(
79/*==========*/
80 ib_wqueue_t* wq, /*!< in: work queue */
81 void* item, /*!< in: work item */
82 mem_heap_t* heap) /*!< in: memory heap to use for allocating the
83 list node */
84{
85 mutex_enter(&wq->mutex);
86
87 ib_list_add_last(wq->items, item, heap);
88 os_event_set(wq->event);
89
90 mutex_exit(&wq->mutex);
91}
92
93/****************************************************************//**
94Wait for a work item to appear in the queue.
95@return work item */
96void*
97ib_wqueue_wait(
98/*===========*/
99 ib_wqueue_t* wq) /*!< in: work queue */
100{
101 ib_list_node_t* node;
102
103 for (;;) {
104 os_event_wait(wq->event);
105
106 mutex_enter(&wq->mutex);
107
108 node = ib_list_get_first(wq->items);
109
110 if (node) {
111 ib_list_remove(wq->items, node);
112
113 if (!ib_list_get_first(wq->items)) {
114 /* We must reset the event when the list
115 gets emptied. */
116 os_event_reset(wq->event);
117 }
118
119 break;
120 }
121
122 mutex_exit(&wq->mutex);
123 }
124
125 mutex_exit(&wq->mutex);
126
127 return(node->data);
128}
129
130
131/********************************************************************
132Wait for a work item to appear in the queue for specified time. */
133void*
134ib_wqueue_timedwait(
135/*================*/
136 /* out: work item or NULL on timeout*/
137 ib_wqueue_t* wq, /* in: work queue */
138 ib_time_t wait_in_usecs) /* in: wait time in micro seconds */
139{
140 ib_list_node_t* node = NULL;
141
142 for (;;) {
143 ulint error;
144 int64_t sig_count;
145
146 mutex_enter(&wq->mutex);
147
148 node = ib_list_get_first(wq->items);
149
150 if (node) {
151 ib_list_remove(wq->items, node);
152
153 mutex_exit(&wq->mutex);
154 break;
155 }
156
157 sig_count = os_event_reset(wq->event);
158
159 mutex_exit(&wq->mutex);
160
161 error = os_event_wait_time_low(wq->event,
162 (ulint) wait_in_usecs,
163 sig_count);
164
165 if (error == OS_SYNC_TIME_EXCEEDED) {
166 break;
167 }
168 }
169
170 return(node ? node->data : NULL);
171}
172
173/********************************************************************
174Return first item on work queue or NULL if queue is empty
175@return work item or NULL */
176void*
177ib_wqueue_nowait(
178/*=============*/
179 ib_wqueue_t* wq) /*<! in: work queue */
180{
181 ib_list_node_t* node = NULL;
182
183 mutex_enter(&wq->mutex);
184
185 if(!ib_list_is_empty(wq->items)) {
186 node = ib_list_get_first(wq->items);
187
188 if (node) {
189 ib_list_remove(wq->items, node);
190
191 }
192 }
193
194 /* We must reset the event when the list
195 gets emptied. */
196 if(ib_list_is_empty(wq->items)) {
197 os_event_reset(wq->event);
198 }
199
200 mutex_exit(&wq->mutex);
201
202 return (node ? node->data : NULL);
203}
204/********************************************************************
205Check if queue is empty. */
206ibool
207ib_wqueue_is_empty(
208/*===============*/
209 /* out: TRUE if queue empty
210 else FALSE */
211 const ib_wqueue_t* wq) /* in: work queue */
212{
213 return(ib_list_is_empty(wq->items));
214}
215
216/********************************************************************
217Get number of items on queue.
218@return number of items on queue */
219ulint
220ib_wqueue_len(
221/*==========*/
222 ib_wqueue_t* wq) /*<! in: work queue */
223{
224 ulint len = 0;
225
226 mutex_enter(&wq->mutex);
227 len = ib_list_len(wq->items);
228 mutex_exit(&wq->mutex);
229
230 return(len);
231}
232