1/*
2 Copyright (c) 2007, 2008, Sun Microsystems, Inc,
3 Copyright (c) 2011, 2012, Monty Program Ab
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; version 2 of the License.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
17
18#include <my_global.h>
19#include <wqueue.h>
20
21#define STRUCT_PTR(TYPE, MEMBER, a) \
22 (TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER))
23/*
24 Link a thread into double-linked queue of waiting threads.
25
26 SYNOPSIS
27 wqueue_link_into_queue()
28 wqueue pointer to the queue structure
29 thread pointer to the thread to be added to the queue
30
31 RETURN VALUE
32 none
33
34 NOTES.
35 Queue is represented by a circular list of the thread structures
36 The list is double-linked of the type (**prev,*next), accessed by
37 a pointer to the last element.
38*/
39
40void wqueue_link_into_queue(WQUEUE *wqueue, struct st_my_thread_var *thread)
41{
42 struct st_my_thread_var *last;
43 if (!(last= wqueue->last_thread))
44 {
45 /* Queue is empty */
46 thread->next= thread;
47 thread->prev= &thread->next;
48 }
49 else
50 {
51 thread->prev= last->next->prev;
52 last->next->prev= &thread->next;
53 thread->next= last->next;
54 last->next= thread;
55 }
56 wqueue->last_thread= thread;
57}
58
59
60/*
61 Add a thread to single-linked queue of waiting threads
62
63 SYNOPSIS
64 wqueue_add_to_queue()
65 wqueue pointer to the queue structure
66 thread pointer to the thread to be added to the queue
67
68 RETURN VALUE
69 none
70
71 NOTES.
72 Queue is represented by a circular list of the thread structures
73 The list is single-linked of the type (*next), accessed by a pointer
74 to the last element.
75*/
76
77void wqueue_add_to_queue(WQUEUE *wqueue, struct st_my_thread_var *thread)
78{
79 struct st_my_thread_var *last;
80 if (!(last= wqueue->last_thread))
81 thread->next= thread;
82 else
83 {
84 thread->next= last->next;
85 last->next= thread;
86 }
87#ifndef DBUG_OFF
88 thread->prev= NULL; /* force segfault if used */
89#endif
90 wqueue->last_thread= thread;
91}
92
93/*
94 Unlink a thread from double-linked queue of waiting threads
95
96 SYNOPSIS
97 wqueue_unlink_from_queue()
98 wqueue pointer to the queue structure
99 thread pointer to the thread to be removed from the queue
100
101 RETURN VALUE
102 none
103
104 NOTES.
105 See NOTES for link_into_queue
106*/
107
108void wqueue_unlink_from_queue(WQUEUE *wqueue, struct st_my_thread_var *thread)
109{
110 if (thread->next == thread)
111 /* The queue contains only one member */
112 wqueue->last_thread= NULL;
113 else
114 {
115 thread->next->prev= thread->prev;
116 *thread->prev= thread->next;
117 if (wqueue->last_thread == thread)
118 wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next,
119 thread->prev);
120 }
121 thread->next= NULL;
122}
123
124
125/*
126 Remove all threads from queue signaling them to proceed
127
128 SYNOPSIS
129 wqueue_realease_queue()
130 wqueue pointer to the queue structure
131 thread pointer to the thread to be added to the queue
132
133 RETURN VALUE
134 none
135
136 NOTES.
137 See notes for add_to_queue
138 When removed from the queue each thread is signaled via condition
139 variable thread->suspend.
140*/
141
142void wqueue_release_queue(WQUEUE *wqueue)
143{
144 struct st_my_thread_var *last= wqueue->last_thread;
145 struct st_my_thread_var *next= last->next;
146 struct st_my_thread_var *thread;
147 do
148 {
149 thread= next;
150 mysql_cond_signal(&thread->suspend);
151 next= thread->next;
152 thread->next= NULL;
153 }
154 while (thread != last);
155 wqueue->last_thread= NULL;
156}
157
158
159/**
160 @brief Removes all threads waiting for read or first one waiting for write.
161
162 @param wqueue pointer to the queue structure
163 @param thread pointer to the thread to be added to the queue
164
165 @note This function is applicable only to single linked lists.
166*/
167
168void wqueue_release_one_locktype_from_queue(WQUEUE *wqueue)
169{
170 struct st_my_thread_var *last= wqueue->last_thread;
171 struct st_my_thread_var *next= last->next;
172 struct st_my_thread_var *thread;
173 struct st_my_thread_var *new_list= NULL;
174 uint first_type= next->lock_type;
175 if (first_type == MY_PTHREAD_LOCK_WRITE)
176 {
177 /* release first waiting for write lock */
178 mysql_cond_signal(&next->suspend);
179 if (next == last)
180 wqueue->last_thread= NULL;
181 else
182 last->next= next->next;
183 next->next= NULL;
184 return;
185 }
186 do
187 {
188 thread= next;
189 next= thread->next;
190 if (thread->lock_type == MY_PTHREAD_LOCK_WRITE)
191 {
192 /* skip waiting for write lock */
193 if (new_list)
194 {
195 thread->next= new_list->next;
196 new_list= new_list->next= thread;
197 }
198 else
199 new_list= thread->next= thread;
200 }
201 else
202 {
203 /* release waiting for read lock */
204 mysql_cond_signal(&thread->suspend);
205 thread->next= NULL;
206 }
207 } while (thread != last);
208 wqueue->last_thread= new_list;
209}
210
211
212/*
213 Add thread and wait
214
215 SYNOPSIS
216 wqueue_add_and_wait()
217 wqueue queue to add to
218 thread thread which is waiting
219 lock mutex need for the operation
220*/
221
222void wqueue_add_and_wait(WQUEUE *wqueue,
223 struct st_my_thread_var *thread,
224 mysql_mutex_t *lock)
225{
226 DBUG_ENTER("wqueue_add_and_wait");
227 DBUG_PRINT("enter",
228 ("thread: %p cond: %p mutex: %p",
229 thread, &thread->suspend, lock));
230 wqueue_add_to_queue(wqueue, thread);
231 do
232 {
233 DBUG_PRINT("info", ("wait... cond: %p mutex: %p",
234 &thread->suspend, lock));
235 mysql_cond_wait(&thread->suspend, lock);
236 DBUG_PRINT("info", ("wait done cond: %p mutex: %p next: %p",
237 &thread->suspend, lock,
238 thread->next));
239 }
240 while (thread->next);
241 DBUG_VOID_RETURN;
242}
243