Parent: [bcf5b0] (diff)

Child: [1de00e] (diff)

Download this file

workqueue.h    358 lines (320 with data), 11.5 kB

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
/* Copyright (C) 2006-2016 J.F.Dockes
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA
*/
#ifndef _WORKQUEUE_H_INCLUDED_
#define _WORKQUEUE_H_INCLUDED_
#include <thread>
#if HAVE_STD_FUTURE
#include <future>
#endif
#include <string>
#include <queue>
#include <list>
#include <mutex>
#include <condition_variable>
#include "log.h"
/**
* A WorkQueue manages the synchronisation around a queue of work items,
* where a number of client threads queue tasks and a number of worker
* threads take and execute them. The goal is to introduce some level
* of parallelism between the successive steps of a previously single
* threaded pipeline. For example data extraction / data preparation / index
* update, but this could have other uses.
*
* There is no individual task status return. In case of fatal error,
* the client or worker sets an end condition on the queue. A second
* queue could conceivably be used for returning individual task
* status.
*
* The strange thread functions argument and return values
* comes from compatibility with an earlier pthread-based
* implementation.
*/
template <class T> class WorkQueue {
public:
/** Create a WorkQueue
* @param name for message printing
* @param hi number of tasks on queue before clients blocks. Default 0
* meaning no limit. hi == -1 means that the queue is disabled.
* @param lo minimum count of tasks before worker starts. Default 1.
*/
WorkQueue(const std::string& name, size_t hi = 0, size_t lo = 1)
: m_name(name), m_high(hi), m_low(lo), m_workers_exited(0),
m_ok(true), m_clients_waiting(0), m_workers_waiting(0),
m_tottasks(0), m_nowake(0), m_workersleeps(0), m_clientsleeps(0) {
}
~WorkQueue() {
if (!m_worker_threads.empty()) {
setTerminateAndWait();
}
}
/** Start the worker threads.
*
* @param nworkers number of threads copies to start.
* @param start_routine thread function. It should loop
* taking (QueueWorker::take()) and executing tasks.
* @param arg initial parameter to thread function.
* @return true if ok.
*/
bool start(int nworkers, void *(workproc)(void *), void *arg) {
std::unique_lock<std::mutex> lock(m_mutex);
for (int i = 0; i < nworkers; i++) {
Worker w;
#if HAVE_STD_FUTURE
std::packaged_task<void *(void *)> task(workproc);
w.res = task.get_future();
w.thr = std::thread(std::move(task), arg);
#else
w.thr = std::thread(workproc, arg);
#endif
m_worker_threads.push_back(std::move(w));
}
return true;
}
/** Add item to work queue, called from client.
*
* Sleeps if there are already too many.
*/
bool put(T t, bool flushprevious = false) {
std::unique_lock<std::mutex> lock(m_mutex);
if (!ok()) {
LOGERR("WorkQueue::put:" << m_name << ": !ok\n");
return false;
}
while (ok() && m_high > 0 && m_queue.size() >= m_high) {
m_clientsleeps++;
// Keep the order: we test ok() AFTER the sleep...
m_clients_waiting++;
m_ccond.wait(lock);
if (!ok()) {
m_clients_waiting--;
return false;
}
m_clients_waiting--;
}
if (flushprevious) {
while (!m_queue.empty()) {
m_queue.pop();
}
}
m_queue.push(t);
if (m_workers_waiting > 0) {
// Just wake one worker, there is only one new task.
m_wcond.notify_one();
} else {
m_nowake++;
}
return true;
}
/** Wait until the queue is inactive. Called from client.
*
* Waits until the task queue is empty and the workers are all
* back sleeping. Used by the client to wait for all current work
* to be completed, when it needs to perform work that couldn't be
* done in parallel with the worker's tasks, or before shutting
* down. Work can be resumed after calling this. Note that the
* only thread which can call it safely is the client just above
* (which can control the task flow), else there could be
* tasks in the intermediate queues.
* To rephrase: there is no warranty on return that the queue is actually
* idle EXCEPT if the caller knows that no jobs are still being created.
* It would be possible to transform this into a safe call if some kind
* of suspend condition was set on the queue by waitIdle(), to be reset by
* some kind of "resume" call. Not currently the case.
*/
bool waitIdle() {
std::unique_lock<std::mutex> lock(m_mutex);
if (!ok()) {
LOGERR("WorkQueue::waitIdle:" << m_name << ": not ok\n");
return false;
}
// We're done when the queue is empty AND all workers are back
// waiting for a task.
while (ok() && (m_queue.size() > 0 ||
m_workers_waiting != m_worker_threads.size())) {
m_clients_waiting++;
m_ccond.wait(lock);
m_clients_waiting--;
}
return ok();
}
/** Tell the workers to exit, and wait for them.
*
* Does not bother about tasks possibly remaining on the queue, so
* should be called after waitIdle() for an orderly shutdown.
*/
void *setTerminateAndWait() {
std::unique_lock<std::mutex> lock(m_mutex);
LOGDEB("setTerminateAndWait:" << m_name << "\n");
if (m_worker_threads.empty()) {
// Already called ?
return (void*)0;
}
// Wait for all worker threads to have called workerExit()
m_ok = false;
while (m_workers_exited < m_worker_threads.size()) {
m_wcond.notify_all();
m_clients_waiting++;
m_ccond.wait(lock);
m_clients_waiting--;
}
LOGINFO("" << m_name << ": tasks " << m_tottasks << " nowakes " <<
m_nowake << " wsleeps " << m_workersleeps << " csleeps " <<
m_clientsleeps << "\n");
// Perform the thread joins and compute overall status
// Workers return (void*)1 if ok
void *statusall = (void*)1;
while (!m_worker_threads.empty()) {
#if HAVE_STD_FUTURE
void *status = m_worker_threads.front().res.get();
#else
void *status = (void*) 1;
#endif
m_worker_threads.front().thr.join();
if (status == (void *)0) {
statusall = status;
}
m_worker_threads.pop_front();
}
// Reset to start state.
m_workers_exited = m_clients_waiting = m_workers_waiting =
m_tottasks = m_nowake = m_workersleeps = m_clientsleeps = 0;
m_ok = true;
LOGDEB("setTerminateAndWait:" << m_name << " done\n");
return statusall;
}
/** Take task from queue. Called from worker.
*
* Sleeps if there are not enough. Signal if we go to sleep on empty
* queue: client may be waiting for our going idle.
*/
bool take(T* tp, size_t *szp = 0) {
std::unique_lock<std::mutex> lock(m_mutex);
if (!ok()) {
LOGDEB("WorkQueue::take:" << m_name << ": not ok\n");
return false;
}
while (ok() && m_queue.size() < m_low) {
m_workersleeps++;
m_workers_waiting++;
if (m_queue.empty()) {
m_ccond.notify_all();
}
m_wcond.wait(lock);
if (!ok()) {
// !ok is a normal condition when shutting down
m_workers_waiting--;
return false;
}
m_workers_waiting--;
}
m_tottasks++;
*tp = m_queue.front();
if (szp) {
*szp = m_queue.size();
}
m_queue.pop();
if (m_clients_waiting > 0) {
// No reason to wake up more than one client thread
m_ccond.notify_one();
} else {
m_nowake++;
}
return true;
}
bool waitminsz(size_t sz) {
std::unique_lock<std::mutex> lock(m_mutex);
if (!ok()) {
return false;
}
while (ok() && m_queue.size() < sz) {
m_workersleeps++;
m_workers_waiting++;
if (m_queue.empty()) {
m_ccond.notify_all();
}
m_wcond.wait(lock);
if (!ok()) {
m_workers_waiting--;
return false;
}
m_workers_waiting--;
}
return true;
}
/** Advertise exit and abort queue. Called from worker
*
* This would happen after an unrecoverable error, or when
* the queue is terminated by the client. Workers never exit normally,
* except when the queue is shut down (at which point m_ok is set to
* false by the shutdown code anyway). The thread must return/exit
* immediately after calling this.
*/
void workerExit() {
LOGDEB("workerExit:" << m_name << "\n");
std::unique_lock<std::mutex> lock(m_mutex);
m_workers_exited++;
m_ok = false;
m_ccond.notify_all();
}
size_t qsize() {
std::unique_lock<std::mutex> lock(m_mutex);
return m_queue.size();
}
private:
bool ok() {
bool isok = m_ok && m_workers_exited == 0 && !m_worker_threads.empty();
if (!isok) {
LOGDEB("WorkQueue:ok:" << m_name << ": not ok m_ok " << m_ok <<
" m_workers_exited " << m_workers_exited <<
" m_worker_threads size " << m_worker_threads.size() <<
"\n");
}
return isok;
}
struct Worker {
std::thread thr;
#if HAVE_STD_FUTURE
std::future<void *> res;
#endif
};
// Configuration
std::string m_name;
size_t m_high;
size_t m_low;
// Worker threads having called exit. Used to decide when we're done
unsigned int m_workers_exited;
// Status
bool m_ok;
// Our threads.
std::list<Worker> m_worker_threads;
// Jobs input queue
std::queue<T> m_queue;
// Synchronization
std::condition_variable m_ccond;
std::condition_variable m_wcond;
std::mutex m_mutex;
// Client/Worker threads currently waiting for a job
unsigned int m_clients_waiting;
unsigned int m_workers_waiting;
// Statistics
unsigned int m_tottasks;
unsigned int m_nowake;
unsigned int m_workersleeps;
unsigned int m_clientsleeps;
};
#endif /* _WORKQUEUE_H_INCLUDED_ */