| 1 | // gold-threads.h -- thread support for gold -*- C++ -*- |
| 2 | |
| 3 | // Copyright (C) 2006-2020 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 | // gold can be configured to support threads. If threads are |
| 24 | // supported, the user can specify at runtime whether or not to |
| 25 | // support them. This provides an interface to manage locking |
| 26 | // accordingly. |
| 27 | |
| 28 | // Lock |
| 29 | // A simple lock class. |
| 30 | |
| 31 | #ifndef GOLD_THREADS_H |
| 32 | #define GOLD_THREADS_H |
| 33 | |
| 34 | namespace gold |
| 35 | { |
| 36 | |
| 37 | class Condvar; |
| 38 | class Once_initialize; |
| 39 | class Initialize_lock_once; |
| 40 | |
| 41 | // The interface for the implementation of a Lock. |
| 42 | |
| 43 | class Lock_impl |
| 44 | { |
| 45 | public: |
| 46 | Lock_impl() |
| 47 | { } |
| 48 | |
| 49 | virtual |
| 50 | ~Lock_impl() |
| 51 | { } |
| 52 | |
| 53 | virtual void |
| 54 | acquire() = 0; |
| 55 | |
| 56 | virtual void |
| 57 | release() = 0; |
| 58 | }; |
| 59 | |
| 60 | // A simple lock class. |
| 61 | |
| 62 | class Lock |
| 63 | { |
| 64 | public: |
| 65 | Lock(); |
| 66 | |
| 67 | ~Lock(); |
| 68 | |
| 69 | // Acquire the lock. |
| 70 | void |
| 71 | acquire() |
| 72 | { this->lock_->acquire(); } |
| 73 | |
| 74 | // Release the lock. |
| 75 | void |
| 76 | release() |
| 77 | { this->lock_->release(); } |
| 78 | |
| 79 | private: |
| 80 | // This class can not be copied. |
| 81 | Lock(const Lock&); |
| 82 | Lock& operator=(const Lock&); |
| 83 | |
| 84 | friend class Condvar; |
| 85 | Lock_impl* |
| 86 | get_impl() const |
| 87 | { return this->lock_; } |
| 88 | |
| 89 | Lock_impl* lock_; |
| 90 | }; |
| 91 | |
| 92 | // RAII for Lock. |
| 93 | |
| 94 | class Hold_lock |
| 95 | { |
| 96 | public: |
| 97 | Hold_lock(Lock& lock) |
| 98 | : lock_(lock) |
| 99 | { this->lock_.acquire(); } |
| 100 | |
| 101 | ~Hold_lock() |
| 102 | { this->lock_.release(); } |
| 103 | |
| 104 | private: |
| 105 | // This class can not be copied. |
| 106 | Hold_lock(const Hold_lock&); |
| 107 | Hold_lock& operator=(const Hold_lock&); |
| 108 | |
| 109 | Lock& lock_; |
| 110 | }; |
| 111 | |
| 112 | class Hold_optional_lock |
| 113 | { |
| 114 | public: |
| 115 | Hold_optional_lock(Lock* lock) |
| 116 | : lock_(lock) |
| 117 | { |
| 118 | if (this->lock_ != NULL) |
| 119 | this->lock_->acquire(); |
| 120 | } |
| 121 | |
| 122 | ~Hold_optional_lock() |
| 123 | { |
| 124 | if (this->lock_ != NULL) |
| 125 | this->lock_->release(); |
| 126 | } |
| 127 | |
| 128 | private: |
| 129 | Hold_optional_lock(const Hold_optional_lock&); |
| 130 | Hold_optional_lock& operator=(const Hold_optional_lock&); |
| 131 | |
| 132 | Lock* lock_; |
| 133 | }; |
| 134 | |
| 135 | // The interface for the implementation of a condition variable. |
| 136 | |
| 137 | class Condvar_impl |
| 138 | { |
| 139 | public: |
| 140 | Condvar_impl() |
| 141 | { } |
| 142 | |
| 143 | virtual |
| 144 | ~Condvar_impl() |
| 145 | { } |
| 146 | |
| 147 | virtual void |
| 148 | wait(Lock_impl*) = 0; |
| 149 | |
| 150 | virtual void |
| 151 | signal() = 0; |
| 152 | |
| 153 | virtual void |
| 154 | broadcast() = 0; |
| 155 | }; |
| 156 | |
| 157 | // A simple condition variable class. It is always associated with a |
| 158 | // specific lock. |
| 159 | |
| 160 | class Condvar |
| 161 | { |
| 162 | public: |
| 163 | Condvar(Lock& lock); |
| 164 | ~Condvar(); |
| 165 | |
| 166 | // Wait for the condition variable to be signalled. This should |
| 167 | // only be called when the lock is held. |
| 168 | void |
| 169 | wait() |
| 170 | { this->condvar_->wait(this->lock_.get_impl()); } |
| 171 | |
| 172 | // Signal the condition variable--wake up at least one thread |
| 173 | // waiting on the condition variable. This should only be called |
| 174 | // when the lock is held. |
| 175 | void |
| 176 | signal() |
| 177 | { this->condvar_->signal(); } |
| 178 | |
| 179 | // Broadcast the condition variable--wake up all threads waiting on |
| 180 | // the condition variable. This should only be called when the lock |
| 181 | // is held. |
| 182 | void |
| 183 | broadcast() |
| 184 | { this->condvar_->broadcast(); } |
| 185 | |
| 186 | private: |
| 187 | // This class can not be copied. |
| 188 | Condvar(const Condvar&); |
| 189 | Condvar& operator=(const Condvar&); |
| 190 | |
| 191 | Lock& lock_; |
| 192 | Condvar_impl* condvar_; |
| 193 | }; |
| 194 | |
| 195 | // A class used to do something once. This is an abstract parent |
| 196 | // class; any actual use will involve a child of this. |
| 197 | |
| 198 | class Once |
| 199 | { |
| 200 | public: |
| 201 | Once(); |
| 202 | |
| 203 | virtual |
| 204 | ~Once() |
| 205 | { } |
| 206 | |
| 207 | // Call this function to do whatever it is. We pass an argument |
| 208 | // even though you have to use a child class because in some uses |
| 209 | // setting the argument would itself require a Once class. |
| 210 | void |
| 211 | run_once(void* arg); |
| 212 | |
| 213 | // This is an internal function, which must be public because it is |
| 214 | // run by an extern "C" function called via pthread_once. |
| 215 | void |
| 216 | internal_run(void* arg); |
| 217 | |
| 218 | protected: |
| 219 | // This must be implemented by the child class. |
| 220 | virtual void |
| 221 | do_run_once(void* arg) = 0; |
| 222 | |
| 223 | private: |
| 224 | // True if we have already run the function. |
| 225 | bool was_run_; |
| 226 | #if defined(ENABLE_THREADS) && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4) |
| 227 | // Internal compare-and-swap lock on was_run_; |
| 228 | uint32_t was_run_lock_; |
| 229 | #endif |
| 230 | // The lock to run the function only once. |
| 231 | Once_initialize* once_; |
| 232 | }; |
| 233 | |
| 234 | // A class used to initialize a lock exactly once, after the options |
| 235 | // have been read. This is needed because the implementation of locks |
| 236 | // depends on whether we've seen the --threads option. Before the |
| 237 | // options have been read, we know we are single-threaded, so we can |
| 238 | // get by without using a lock. This class should be an instance |
| 239 | // variable of the class which has a lock which needs to be |
| 240 | // initialized. |
| 241 | |
| 242 | class Initialize_lock : public Once |
| 243 | { |
| 244 | public: |
| 245 | // The class which uses this will have a pointer to a lock. This |
| 246 | // must be constructed with a pointer to that pointer. |
| 247 | Initialize_lock(Lock** pplock) |
| 248 | : pplock_(pplock) |
| 249 | { } |
| 250 | |
| 251 | // Initialize the lock. Return true if the lock is now initialized, |
| 252 | // false if it is not (because the options have not yet been read). |
| 253 | bool |
| 254 | initialize(); |
| 255 | |
| 256 | protected: |
| 257 | void |
| 258 | do_run_once(void*); |
| 259 | |
| 260 | private: |
| 261 | // A pointer to the lock pointer which must be initialized. |
| 262 | Lock** const pplock_; |
| 263 | }; |
| 264 | |
| 265 | } // End namespace gold. |
| 266 | |
| 267 | #endif // !defined(GOLD_THREADS_H) |