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
|
// workqueue-threads.cc -- the threaded workqueue for gold
// Copyright (C) 2007-2020 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// 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 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 Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
// This file holds the workqueue implementation which may be used when
// using threads.
#include "gold.h"
#ifdef ENABLE_THREADS
#include <cstring>
#include <pthread.h>
#include "debug.h"
#include "gold-threads.h"
#include "workqueue.h"
#include "workqueue-internal.h"
namespace gold
{
// Class Workqueue_thread represents a single thread. Creating an
// instance of this spawns a new thread.
class Workqueue_thread
{
public:
Workqueue_thread(Workqueue_threader_threadpool*, int thread_number);
~Workqueue_thread();
private:
// This class can not be copied.
Workqueue_thread(const Workqueue_thread&);
Workqueue_thread& operator=(const Workqueue_thread&);
// Check for error from a pthread function.
void
check(const char* function, int err) const;
// A function to pass to pthread_create. This is called with a
// pointer to an instance of this object.
static void*
thread_body(void*);
// A pointer to the threadpool that this thread is part of.
Workqueue_threader_threadpool* threadpool_;
// The thread number.
int thread_number_;
// The thread ID.
pthread_t tid_;
};
// Create the thread in the constructor.
Workqueue_thread::Workqueue_thread(Workqueue_threader_threadpool* threadpool,
int thread_number)
: threadpool_(threadpool), thread_number_(thread_number)
{
pthread_attr_t attr;
int err = pthread_attr_init(&attr);
this->check("pthread_attr_init", err);
err = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
this->check("pthread_attr_setdetachstate", err);
err = pthread_create(&this->tid_, &attr, &Workqueue_thread::thread_body,
reinterpret_cast<void*>(this));
this->check("pthread_create", err);
err = pthread_attr_destroy(&attr);
this->check("pthread_attr_destroy", err);
}
// The destructor will be called when the thread is exiting.
Workqueue_thread::~Workqueue_thread()
{
}
// Check for an error.
void
Workqueue_thread::check(const char* function, int err) const
{
if (err != 0)
gold_fatal(_("%s failed: %s"), function, strerror(err));
}
// Passed to pthread_create.
extern "C"
void*
Workqueue_thread::thread_body(void* arg)
{
Workqueue_thread* pwt = reinterpret_cast<Workqueue_thread*>(arg);
pwt->threadpool_->process(pwt->thread_number_);
// Delete the thread object as we exit.
delete pwt;
return NULL;
}
// Class Workqueue_threader_threadpool.
// Constructor.
Workqueue_threader_threadpool::Workqueue_threader_threadpool(
Workqueue* workqueue)
: Workqueue_threader(workqueue),
check_thread_count_(0),
lock_(),
desired_thread_count_(1),
threads_(1)
{
}
// Destructor.
Workqueue_threader_threadpool::~Workqueue_threader_threadpool()
{
// Tell the threads to exit.
this->get_workqueue()->set_thread_count(0);
}
// Set the thread count.
void
Workqueue_threader_threadpool::set_thread_count(int thread_count)
{
int create;
{
Hold_lock hl(this->lock_);
this->desired_thread_count_ = thread_count;
create = this->desired_thread_count_ - this->threads_;
if (create < 0)
this->check_thread_count_ = 1;
}
if (create > 0)
{
for (int i = 0; i < create; ++i)
{
// Note that threads delete themselves when they exit, so we
// don't keep pointers to them.
new Workqueue_thread(this, this->threads_);
++this->threads_;
}
}
}
// Return whether the current thread should be cancelled.
bool
Workqueue_threader_threadpool::should_cancel_thread(int thread_number)
{
// Fast exit without taking a lock.
if (!this->check_thread_count_)
return false;
{
Hold_lock hl(this->lock_);
if (thread_number > this->desired_thread_count_)
{
--this->threads_;
if (this->threads_ <= this->desired_thread_count_)
this->check_thread_count_ = 0;
return true;
}
}
return false;
}
} // End namespace gold.
#endif // defined(ENABLE_THREADS)
|
