| 1 | // workqueue-threads.cc -- the threaded workqueue for gold |
| 2 | |
| 3 | // Copyright (C) 2007-2020 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 | |
| 23 | // This file holds the workqueue implementation which may be used when |
| 24 | // using threads. |
| 25 | |
| 26 | #include "gold.h" |
| 27 | |
| 28 | #ifdef ENABLE_THREADS |
| 29 | |
| 30 | #include <cstring> |
| 31 | #include <pthread.h> |
| 32 | |
| 33 | #include "debug.h" |
| 34 | #include "gold-threads.h" |
| 35 | #include "workqueue.h" |
| 36 | #include "workqueue-internal.h" |
| 37 | |
| 38 | namespace gold |
| 39 | { |
| 40 | |
| 41 | // Class Workqueue_thread represents a single thread. Creating an |
| 42 | // instance of this spawns a new thread. |
| 43 | |
| 44 | class Workqueue_thread |
| 45 | { |
| 46 | public: |
| 47 | Workqueue_thread(Workqueue_threader_threadpool*, int thread_number); |
| 48 | |
| 49 | ~Workqueue_thread(); |
| 50 | |
| 51 | private: |
| 52 | // This class can not be copied. |
| 53 | Workqueue_thread(const Workqueue_thread&); |
| 54 | Workqueue_thread& operator=(const Workqueue_thread&); |
| 55 | |
| 56 | // Check for error from a pthread function. |
| 57 | void |
| 58 | check(const char* function, int err) const; |
| 59 | |
| 60 | // A function to pass to pthread_create. This is called with a |
| 61 | // pointer to an instance of this object. |
| 62 | static void* |
| 63 | thread_body(void*); |
| 64 | |
| 65 | // A pointer to the threadpool that this thread is part of. |
| 66 | Workqueue_threader_threadpool* threadpool_; |
| 67 | // The thread number. |
| 68 | int thread_number_; |
| 69 | // The thread ID. |
| 70 | pthread_t tid_; |
| 71 | }; |
| 72 | |
| 73 | // Create the thread in the constructor. |
| 74 | |
| 75 | Workqueue_thread::Workqueue_thread(Workqueue_threader_threadpool* threadpool, |
| 76 | int thread_number) |
| 77 | : threadpool_(threadpool), thread_number_(thread_number) |
| 78 | { |
| 79 | pthread_attr_t attr; |
| 80 | int err = pthread_attr_init(&attr); |
| 81 | this->check("pthread_attr_init", err); |
| 82 | |
| 83 | err = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); |
| 84 | this->check("pthread_attr_setdetachstate", err); |
| 85 | |
| 86 | err = pthread_create(&this->tid_, &attr, &Workqueue_thread::thread_body, |
| 87 | reinterpret_cast<void*>(this)); |
| 88 | this->check("pthread_create", err); |
| 89 | |
| 90 | err = pthread_attr_destroy(&attr); |
| 91 | this->check("pthread_attr_destroy", err); |
| 92 | } |
| 93 | |
| 94 | // The destructor will be called when the thread is exiting. |
| 95 | |
| 96 | Workqueue_thread::~Workqueue_thread() |
| 97 | { |
| 98 | } |
| 99 | |
| 100 | // Check for an error. |
| 101 | |
| 102 | void |
| 103 | Workqueue_thread::check(const char* function, int err) const |
| 104 | { |
| 105 | if (err != 0) |
| 106 | gold_fatal(_("%s failed: %s"), function, strerror(err)); |
| 107 | } |
| 108 | |
| 109 | // Passed to pthread_create. |
| 110 | |
| 111 | extern "C" |
| 112 | void* |
| 113 | Workqueue_thread::thread_body(void* arg) |
| 114 | { |
| 115 | Workqueue_thread* pwt = reinterpret_cast<Workqueue_thread*>(arg); |
| 116 | |
| 117 | pwt->threadpool_->process(pwt->thread_number_); |
| 118 | |
| 119 | // Delete the thread object as we exit. |
| 120 | delete pwt; |
| 121 | |
| 122 | return NULL; |
| 123 | } |
| 124 | |
| 125 | // Class Workqueue_threader_threadpool. |
| 126 | |
| 127 | // Constructor. |
| 128 | |
| 129 | Workqueue_threader_threadpool::Workqueue_threader_threadpool( |
| 130 | Workqueue* workqueue) |
| 131 | : Workqueue_threader(workqueue), |
| 132 | check_thread_count_(0), |
| 133 | lock_(), |
| 134 | desired_thread_count_(1), |
| 135 | threads_(1) |
| 136 | { |
| 137 | } |
| 138 | |
| 139 | // Destructor. |
| 140 | |
| 141 | Workqueue_threader_threadpool::~Workqueue_threader_threadpool() |
| 142 | { |
| 143 | // Tell the threads to exit. |
| 144 | this->get_workqueue()->set_thread_count(0); |
| 145 | } |
| 146 | |
| 147 | // Set the thread count. |
| 148 | |
| 149 | void |
| 150 | Workqueue_threader_threadpool::set_thread_count(int thread_count) |
| 151 | { |
| 152 | int create; |
| 153 | { |
| 154 | Hold_lock hl(this->lock_); |
| 155 | |
| 156 | this->desired_thread_count_ = thread_count; |
| 157 | create = this->desired_thread_count_ - this->threads_; |
| 158 | if (create < 0) |
| 159 | this->check_thread_count_ = 1; |
| 160 | } |
| 161 | |
| 162 | if (create > 0) |
| 163 | { |
| 164 | for (int i = 0; i < create; ++i) |
| 165 | { |
| 166 | // Note that threads delete themselves when they exit, so we |
| 167 | // don't keep pointers to them. |
| 168 | new Workqueue_thread(this, this->threads_); |
| 169 | ++this->threads_; |
| 170 | } |
| 171 | } |
| 172 | } |
| 173 | |
| 174 | // Return whether the current thread should be cancelled. |
| 175 | |
| 176 | bool |
| 177 | Workqueue_threader_threadpool::should_cancel_thread(int thread_number) |
| 178 | { |
| 179 | // Fast exit without taking a lock. |
| 180 | if (!this->check_thread_count_) |
| 181 | return false; |
| 182 | |
| 183 | { |
| 184 | Hold_lock hl(this->lock_); |
| 185 | if (thread_number > this->desired_thread_count_) |
| 186 | { |
| 187 | --this->threads_; |
| 188 | if (this->threads_ <= this->desired_thread_count_) |
| 189 | this->check_thread_count_ = 0; |
| 190 | return true; |
| 191 | } |
| 192 | } |
| 193 | |
| 194 | return false; |
| 195 | } |
| 196 | |
| 197 | } // End namespace gold. |
| 198 | |
| 199 | #endif // defined(ENABLE_THREADS) |