Commit | Line | Data |
---|---|---|
bae7f79e ILT |
1 | // workqueue.cc -- the workqueue for gold |
2 | ||
6cb15b7f ILT |
3 | // Copyright 2006, 2007 Free Software Foundation, Inc. |
4 | // Written by Ian Lance Taylor <iant@google.com>. | |
5 | ||
6 | // This file is part of gold. | |
7 | ||
8 | // This program is free software; you can redistribute it and/or modify | |
9 | // it under the terms of the GNU General Public License as published by | |
10 | // the Free Software Foundation; either version 3 of the License, or | |
11 | // (at your option) any later version. | |
12 | ||
13 | // This program is distributed in the hope that it will be useful, | |
14 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | // GNU General Public License for more details. | |
17 | ||
18 | // You should have received a copy of the GNU General Public License | |
19 | // along with this program; if not, write to the Free Software | |
20 | // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, | |
21 | // MA 02110-1301, USA. | |
22 | ||
bae7f79e | 23 | #include "gold.h" |
c33feb2b | 24 | |
bae7f79e ILT |
25 | #include "workqueue.h" |
26 | ||
27 | namespace gold | |
28 | { | |
29 | ||
30 | // Task_token methods. | |
31 | ||
32 | Task_token::Task_token() | |
33 | : is_blocker_(false), readers_(0), writer_(NULL) | |
34 | { | |
35 | } | |
36 | ||
37 | Task_token::~Task_token() | |
38 | { | |
a3ad94ed | 39 | gold_assert(this->readers_ == 0 && this->writer_ == NULL); |
bae7f79e ILT |
40 | } |
41 | ||
42 | bool | |
43 | Task_token::is_readable() const | |
44 | { | |
a3ad94ed | 45 | gold_assert(!this->is_blocker_); |
bae7f79e ILT |
46 | return this->writer_ == NULL; |
47 | } | |
48 | ||
49 | void | |
50 | Task_token::add_reader() | |
51 | { | |
a3ad94ed ILT |
52 | gold_assert(!this->is_blocker_); |
53 | gold_assert(this->is_readable()); | |
bae7f79e ILT |
54 | ++this->readers_; |
55 | } | |
56 | ||
57 | void | |
58 | Task_token::remove_reader() | |
59 | { | |
a3ad94ed ILT |
60 | gold_assert(!this->is_blocker_); |
61 | gold_assert(this->readers_ > 0); | |
bae7f79e ILT |
62 | --this->readers_; |
63 | } | |
64 | ||
65 | bool | |
66 | Task_token::is_writable() const | |
67 | { | |
a3ad94ed | 68 | gold_assert(!this->is_blocker_); |
bae7f79e ILT |
69 | return this->writer_ == NULL && this->readers_ == 0; |
70 | } | |
71 | ||
72 | void | |
73 | Task_token::add_writer(const Task* t) | |
74 | { | |
a3ad94ed ILT |
75 | gold_assert(!this->is_blocker_); |
76 | gold_assert(this->is_writable()); | |
bae7f79e ILT |
77 | this->writer_ = t; |
78 | } | |
79 | ||
80 | void | |
81 | Task_token::remove_writer(const Task* t) | |
82 | { | |
a3ad94ed ILT |
83 | gold_assert(!this->is_blocker_); |
84 | gold_assert(this->writer_ == t); | |
bae7f79e ILT |
85 | this->writer_ = NULL; |
86 | } | |
87 | ||
88 | bool | |
89 | Task_token::has_write_lock(const Task* t) | |
90 | { | |
a3ad94ed | 91 | gold_assert(!this->is_blocker_); |
bae7f79e ILT |
92 | return this->writer_ == t; |
93 | } | |
94 | ||
95 | // For blockers, we just use the readers_ field. | |
96 | ||
97 | void | |
98 | Task_token::add_blocker() | |
99 | { | |
100 | if (this->readers_ == 0 && this->writer_ == NULL) | |
101 | this->is_blocker_ = true; | |
102 | else | |
a3ad94ed | 103 | gold_assert(this->is_blocker_); |
bae7f79e ILT |
104 | ++this->readers_; |
105 | } | |
106 | ||
107 | bool | |
108 | Task_token::remove_blocker() | |
109 | { | |
a3ad94ed | 110 | gold_assert(this->is_blocker_ && this->readers_ > 0); |
bae7f79e ILT |
111 | --this->readers_; |
112 | return this->readers_ == 0; | |
113 | } | |
114 | ||
115 | bool | |
116 | Task_token::is_blocked() const | |
117 | { | |
a3ad94ed ILT |
118 | gold_assert(this->is_blocker_ |
119 | || (this->readers_ == 0 && this->writer_ == NULL)); | |
bae7f79e ILT |
120 | return this->readers_ > 0; |
121 | } | |
122 | ||
123 | // The Task_block_token class. | |
124 | ||
125 | Task_block_token::Task_block_token(Task_token& token, Workqueue* workqueue) | |
126 | : token_(token), workqueue_(workqueue) | |
127 | { | |
128 | // We must increment the block count when the task is created and | |
129 | // put on the queue. This object is created when the task is run, | |
130 | // so we don't increment the block count here. | |
a3ad94ed | 131 | gold_assert(this->token_.is_blocked()); |
bae7f79e ILT |
132 | } |
133 | ||
134 | Task_block_token::~Task_block_token() | |
135 | { | |
136 | if (this->token_.remove_blocker()) | |
137 | { | |
138 | // Tell the workqueue that a blocker was cleared. This is | |
139 | // always called in the main thread, so no locking is required. | |
140 | this->workqueue_->cleared_blocker(); | |
141 | } | |
142 | } | |
143 | ||
144 | // The Workqueue_runner abstract class. | |
145 | ||
146 | class Workqueue_runner | |
147 | { | |
148 | public: | |
149 | Workqueue_runner(Workqueue* workqueue) | |
150 | : workqueue_(workqueue) | |
151 | { } | |
152 | virtual ~Workqueue_runner() | |
153 | { } | |
154 | ||
155 | // Run a task. This is always called in the main thread. | |
156 | virtual void run(Task*, Task_locker*) = 0; | |
157 | ||
158 | protected: | |
159 | // This is called by an implementation when a task is completed. | |
160 | void completed(Task* t, Task_locker* tl) | |
161 | { this->workqueue_->completed(t, tl); } | |
162 | ||
163 | Workqueue* get_workqueue() const | |
164 | { return this->workqueue_; } | |
165 | ||
166 | private: | |
167 | Workqueue* workqueue_; | |
168 | }; | |
169 | ||
170 | // The simple single-threaded implementation of Workqueue_runner. | |
171 | ||
172 | class Workqueue_runner_single : public Workqueue_runner | |
173 | { | |
174 | public: | |
175 | Workqueue_runner_single(Workqueue* workqueue) | |
176 | : Workqueue_runner(workqueue) | |
177 | { } | |
178 | ~Workqueue_runner_single() | |
179 | { } | |
180 | ||
181 | void run(Task*, Task_locker*); | |
182 | }; | |
183 | ||
184 | void | |
185 | Workqueue_runner_single::run(Task* t, Task_locker* tl) | |
186 | { | |
187 | t->run(this->get_workqueue()); | |
188 | this->completed(t, tl); | |
189 | } | |
190 | ||
191 | // Workqueue methods. | |
192 | ||
193 | Workqueue::Workqueue(const General_options&) | |
194 | : tasks_lock_(), | |
195 | tasks_(), | |
196 | completed_lock_(), | |
197 | completed_(), | |
198 | running_(0), | |
199 | completed_condvar_(this->completed_lock_), | |
200 | cleared_blockers_(0) | |
201 | { | |
202 | // At some point we will select the specific implementation of | |
203 | // Workqueue_runner to use based on the command line options. | |
204 | this->runner_ = new Workqueue_runner_single(this); | |
205 | } | |
206 | ||
207 | Workqueue::~Workqueue() | |
208 | { | |
a3ad94ed ILT |
209 | gold_assert(this->tasks_.empty()); |
210 | gold_assert(this->completed_.empty()); | |
211 | gold_assert(this->running_ == 0); | |
bae7f79e ILT |
212 | } |
213 | ||
92e059d8 ILT |
214 | // Add a task to the queue. |
215 | ||
bae7f79e ILT |
216 | void |
217 | Workqueue::queue(Task* t) | |
218 | { | |
219 | Hold_lock hl(this->tasks_lock_); | |
220 | this->tasks_.push_back(t); | |
221 | } | |
222 | ||
92e059d8 ILT |
223 | // Add a task to the front of the queue. |
224 | ||
225 | void | |
226 | Workqueue::queue_front(Task* t) | |
227 | { | |
228 | Hold_lock hl(this->tasks_lock_); | |
229 | this->tasks_.push_front(t); | |
230 | } | |
231 | ||
bae7f79e ILT |
232 | // Clear the list of completed tasks. Return whether we cleared |
233 | // anything. The completed_lock_ must be held when this is called. | |
234 | ||
235 | bool | |
236 | Workqueue::clear_completed() | |
237 | { | |
238 | if (this->completed_.empty()) | |
239 | return false; | |
240 | do | |
241 | { | |
242 | delete this->completed_.front(); | |
243 | this->completed_.pop_front(); | |
244 | } | |
245 | while (!this->completed_.empty()); | |
246 | return true; | |
247 | } | |
248 | ||
249 | // Find a runnable task in TASKS, which is non-empty. Return NULL if | |
250 | // none could be found. The tasks_lock_ must be held when this is | |
251 | // called. Sets ALL_BLOCKED if all non-runnable tasks are waiting on | |
252 | // a blocker. | |
253 | ||
254 | Task* | |
255 | Workqueue::find_runnable(Task_list& tasks, bool* all_blocked) | |
256 | { | |
257 | Task* tlast = tasks.back(); | |
258 | *all_blocked = true; | |
259 | while (true) | |
260 | { | |
261 | Task* t = tasks.front(); | |
262 | tasks.pop_front(); | |
263 | ||
264 | Task::Is_runnable_type is_runnable = t->is_runnable(this); | |
265 | if (is_runnable == Task::IS_RUNNABLE) | |
266 | return t; | |
267 | ||
268 | if (is_runnable != Task::IS_BLOCKED) | |
269 | *all_blocked = false; | |
270 | ||
271 | tasks.push_back(t); | |
272 | ||
273 | if (t == tlast) | |
274 | { | |
275 | // We couldn't find any runnable task. If there are any | |
276 | // completed tasks, free their locks and try again. | |
277 | ||
278 | { | |
279 | Hold_lock hl2(this->completed_lock_); | |
280 | ||
281 | if (!this->clear_completed()) | |
282 | { | |
283 | // There had better be some tasks running, or we will | |
284 | // never find a runnable task. | |
a3ad94ed | 285 | gold_assert(this->running_ > 0); |
bae7f79e ILT |
286 | |
287 | // We couldn't find any runnable tasks, and we | |
288 | // couldn't release any locks. | |
289 | return NULL; | |
290 | } | |
291 | } | |
292 | ||
293 | // We're going around again, so recompute ALL_BLOCKED. | |
294 | *all_blocked = true; | |
295 | } | |
296 | } | |
297 | } | |
298 | ||
299 | // Process all the tasks on the workqueue. This is the main loop in | |
300 | // the linker. Note that as we process tasks, new tasks will be | |
301 | // added. | |
302 | ||
303 | void | |
304 | Workqueue::process() | |
305 | { | |
306 | while (true) | |
307 | { | |
308 | Task* t; | |
309 | bool empty; | |
310 | bool all_blocked; | |
311 | ||
312 | { | |
313 | Hold_lock hl(this->tasks_lock_); | |
314 | ||
315 | if (this->tasks_.empty()) | |
316 | { | |
317 | t = NULL; | |
318 | empty = true; | |
319 | all_blocked = false; | |
320 | } | |
321 | else | |
322 | { | |
323 | t = this->find_runnable(this->tasks_, &all_blocked); | |
324 | empty = false; | |
325 | } | |
326 | } | |
327 | ||
328 | // If T != NULL, it is a task we can run. | |
329 | // If T == NULL && empty, then there are no tasks waiting to | |
330 | // be run at this level. | |
331 | // If T == NULL && !empty, then there tasks waiting to be | |
332 | // run at this level, but they are waiting for something to | |
333 | // unlock. | |
334 | ||
335 | if (t != NULL) | |
336 | this->run(t); | |
337 | else if (!empty) | |
338 | { | |
339 | { | |
340 | Hold_lock hl(this->completed_lock_); | |
341 | ||
342 | // There must be something for us to wait for, or we won't | |
343 | // be able to make progress. | |
a3ad94ed | 344 | gold_assert(this->running_ > 0 || !this->completed_.empty()); |
bae7f79e ILT |
345 | |
346 | if (all_blocked) | |
347 | { | |
348 | this->cleared_blockers_ = 0; | |
349 | this->clear_completed(); | |
350 | while (this->cleared_blockers_ == 0) | |
351 | { | |
a3ad94ed | 352 | gold_assert(this->running_ > 0); |
bae7f79e ILT |
353 | this->completed_condvar_.wait(); |
354 | this->clear_completed(); | |
355 | } | |
356 | } | |
357 | else | |
358 | { | |
359 | if (this->running_ > 0) | |
360 | { | |
361 | // Wait for a task to finish. | |
362 | this->completed_condvar_.wait(); | |
363 | } | |
364 | this->clear_completed(); | |
365 | } | |
366 | } | |
367 | } | |
368 | else | |
369 | { | |
370 | { | |
371 | Hold_lock hl(this->completed_lock_); | |
372 | ||
373 | // If there are no running tasks, then we are done. | |
374 | if (this->running_ == 0) | |
375 | { | |
376 | this->clear_completed(); | |
377 | return; | |
378 | } | |
379 | ||
380 | // Wait for a task to finish. Then we have to loop around | |
381 | // again in case it added any new tasks before finishing. | |
382 | this->completed_condvar_.wait(); | |
383 | this->clear_completed(); | |
384 | } | |
385 | } | |
386 | } | |
387 | } | |
388 | ||
389 | // Run a task. This is always called in the main thread. | |
390 | ||
391 | void | |
392 | Workqueue::run(Task* t) | |
393 | { | |
394 | ++this->running_; | |
395 | this->runner_->run(t, t->locks(this)); | |
396 | } | |
397 | ||
398 | // This is called when a task is completed to put the locks on the | |
399 | // list to be released. We use a list because we only want the locks | |
400 | // to be released in the main thread. | |
401 | ||
402 | void | |
403 | Workqueue::completed(Task* t, Task_locker* tl) | |
404 | { | |
405 | { | |
406 | Hold_lock hl(this->completed_lock_); | |
a3ad94ed | 407 | gold_assert(this->running_ > 0); |
bae7f79e ILT |
408 | --this->running_; |
409 | this->completed_.push_back(tl); | |
410 | this->completed_condvar_.signal(); | |
411 | } | |
412 | delete t; | |
413 | } | |
414 | ||
415 | // This is called when the last task for a blocker has completed. | |
416 | // This is always called in the main thread. | |
417 | ||
418 | void | |
419 | Workqueue::cleared_blocker() | |
420 | { | |
421 | ++this->cleared_blockers_; | |
422 | } | |
423 | ||
424 | } // End namespace gold. |