1 //===--- LockFileManager.cpp - File-level Locking Utility------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "llvm/Support/LockFileManager.h" 10 #include "llvm/ADT/None.h" 11 #include "llvm/ADT/SmallVector.h" 12 #include "llvm/ADT/StringExtras.h" 13 #include "llvm/Support/Errc.h" 14 #include "llvm/Support/ErrorOr.h" 15 #include "llvm/Support/FileSystem.h" 16 #include "llvm/Support/MemoryBuffer.h" 17 #include "llvm/Support/Signals.h" 18 #include "llvm/Support/raw_ostream.h" 19 #include <cerrno> 20 #include <ctime> 21 #include <memory> 22 #include <sys/stat.h> 23 #include <sys/types.h> 24 #include <system_error> 25 #include <tuple> 26 #ifdef _WIN32 27 #include <windows.h> 28 #endif 29 #if LLVM_ON_UNIX 30 #include <unistd.h> 31 #endif 32 33 #if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050) 34 #define USE_OSX_GETHOSTUUID 1 35 #else 36 #define USE_OSX_GETHOSTUUID 0 37 #endif 38 39 #if USE_OSX_GETHOSTUUID 40 #include <uuid/uuid.h> 41 #endif 42 43 using namespace llvm; 44 45 /// Attempt to read the lock file with the given name, if it exists. 46 /// 47 /// \param LockFileName The name of the lock file to read. 48 /// 49 /// \returns The process ID of the process that owns this lock file 50 Optional<std::pair<std::string, int> > 51 LockFileManager::readLockFile(StringRef LockFileName) { 52 // Read the owning host and PID out of the lock file. If it appears that the 53 // owning process is dead, the lock file is invalid. 54 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 55 MemoryBuffer::getFile(LockFileName); 56 if (!MBOrErr) { 57 sys::fs::remove(LockFileName); 58 return None; 59 } 60 MemoryBuffer &MB = *MBOrErr.get(); 61 62 StringRef Hostname; 63 StringRef PIDStr; 64 std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " "); 65 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" ")); 66 int PID; 67 if (!PIDStr.getAsInteger(10, PID)) { 68 auto Owner = std::make_pair(std::string(Hostname), PID); 69 if (processStillExecuting(Owner.first, Owner.second)) 70 return Owner; 71 } 72 73 // Delete the lock file. It's invalid anyway. 74 sys::fs::remove(LockFileName); 75 return None; 76 } 77 78 static std::error_code getHostID(SmallVectorImpl<char> &HostID) { 79 HostID.clear(); 80 81 #if USE_OSX_GETHOSTUUID 82 // On OS X, use the more stable hardware UUID instead of hostname. 83 struct timespec wait = {1, 0}; // 1 second. 84 uuid_t uuid; 85 if (gethostuuid(uuid, &wait) != 0) 86 return std::error_code(errno, std::system_category()); 87 88 uuid_string_t UUIDStr; 89 uuid_unparse(uuid, UUIDStr); 90 StringRef UUIDRef(UUIDStr); 91 HostID.append(UUIDRef.begin(), UUIDRef.end()); 92 93 #elif LLVM_ON_UNIX 94 char HostName[256]; 95 HostName[255] = 0; 96 HostName[0] = 0; 97 gethostname(HostName, 255); 98 StringRef HostNameRef(HostName); 99 HostID.append(HostNameRef.begin(), HostNameRef.end()); 100 101 #else 102 StringRef Dummy("localhost"); 103 HostID.append(Dummy.begin(), Dummy.end()); 104 #endif 105 106 return std::error_code(); 107 } 108 109 bool LockFileManager::processStillExecuting(StringRef HostID, int PID) { 110 #if LLVM_ON_UNIX && !defined(__ANDROID__) 111 SmallString<256> StoredHostID; 112 if (getHostID(StoredHostID)) 113 return true; // Conservatively assume it's executing on error. 114 115 // Check whether the process is dead. If so, we're done. 116 if (StoredHostID == HostID && getsid(PID) == -1 && errno == ESRCH) 117 return false; 118 #endif 119 120 return true; 121 } 122 123 namespace { 124 125 /// An RAII helper object ensure that the unique lock file is removed. 126 /// 127 /// Ensures that if there is an error or a signal before we finish acquiring the 128 /// lock, the unique file will be removed. And if we successfully take the lock, 129 /// the signal handler is left in place so that signals while the lock is held 130 /// will remove the unique lock file. The caller should ensure there is a 131 /// matching call to sys::DontRemoveFileOnSignal when the lock is released. 132 class RemoveUniqueLockFileOnSignal { 133 StringRef Filename; 134 bool RemoveImmediately; 135 public: 136 RemoveUniqueLockFileOnSignal(StringRef Name) 137 : Filename(Name), RemoveImmediately(true) { 138 sys::RemoveFileOnSignal(Filename, nullptr); 139 } 140 141 ~RemoveUniqueLockFileOnSignal() { 142 if (!RemoveImmediately) { 143 // Leave the signal handler enabled. It will be removed when the lock is 144 // released. 145 return; 146 } 147 sys::fs::remove(Filename); 148 sys::DontRemoveFileOnSignal(Filename); 149 } 150 151 void lockAcquired() { RemoveImmediately = false; } 152 }; 153 154 } // end anonymous namespace 155 156 LockFileManager::LockFileManager(StringRef FileName) 157 { 158 this->FileName = FileName; 159 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) { 160 std::string S("failed to obtain absolute path for "); 161 S.append(this->FileName.str()); 162 setError(EC, S); 163 return; 164 } 165 LockFileName = this->FileName; 166 LockFileName += ".lock"; 167 168 // If the lock file already exists, don't bother to try to create our own 169 // lock file; it won't work anyway. Just figure out who owns this lock file. 170 if ((Owner = readLockFile(LockFileName))) 171 return; 172 173 // Create a lock file that is unique to this instance. 174 UniqueLockFileName = LockFileName; 175 UniqueLockFileName += "-%%%%%%%%"; 176 int UniqueLockFileID; 177 if (std::error_code EC = sys::fs::createUniqueFile( 178 UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) { 179 std::string S("failed to create unique file "); 180 S.append(UniqueLockFileName.str()); 181 setError(EC, S); 182 return; 183 } 184 185 // Write our process ID to our unique lock file. 186 { 187 SmallString<256> HostID; 188 if (auto EC = getHostID(HostID)) { 189 setError(EC, "failed to get host id"); 190 return; 191 } 192 193 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true); 194 Out << HostID << ' '; 195 #if LLVM_ON_UNIX 196 Out << getpid(); 197 #else 198 Out << "1"; 199 #endif 200 Out.close(); 201 202 if (Out.has_error()) { 203 // We failed to write out PID, so report the error, remove the 204 // unique lock file, and fail. 205 std::string S("failed to write to "); 206 S.append(UniqueLockFileName.str()); 207 setError(Out.error(), S); 208 sys::fs::remove(UniqueLockFileName); 209 return; 210 } 211 } 212 213 // Clean up the unique file on signal, which also releases the lock if it is 214 // held since the .lock symlink will point to a nonexistent file. 215 RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName); 216 217 while (true) { 218 // Create a link from the lock file name. If this succeeds, we're done. 219 std::error_code EC = 220 sys::fs::create_link(UniqueLockFileName, LockFileName); 221 if (!EC) { 222 RemoveUniqueFile.lockAcquired(); 223 return; 224 } 225 226 if (EC != errc::file_exists) { 227 std::string S("failed to create link "); 228 raw_string_ostream OSS(S); 229 OSS << LockFileName.str() << " to " << UniqueLockFileName.str(); 230 setError(EC, OSS.str()); 231 return; 232 } 233 234 // Someone else managed to create the lock file first. Read the process ID 235 // from the lock file. 236 if ((Owner = readLockFile(LockFileName))) { 237 // Wipe out our unique lock file (it's useless now) 238 sys::fs::remove(UniqueLockFileName); 239 return; 240 } 241 242 if (!sys::fs::exists(LockFileName)) { 243 // The previous owner released the lock file before we could read it. 244 // Try to get ownership again. 245 continue; 246 } 247 248 // There is a lock file that nobody owns; try to clean it up and get 249 // ownership. 250 if ((EC = sys::fs::remove(LockFileName))) { 251 std::string S("failed to remove lockfile "); 252 S.append(UniqueLockFileName.str()); 253 setError(EC, S); 254 return; 255 } 256 } 257 } 258 259 LockFileManager::LockFileState LockFileManager::getState() const { 260 if (Owner) 261 return LFS_Shared; 262 263 if (ErrorCode) 264 return LFS_Error; 265 266 return LFS_Owned; 267 } 268 269 std::string LockFileManager::getErrorMessage() const { 270 if (ErrorCode) { 271 std::string Str(ErrorDiagMsg); 272 std::string ErrCodeMsg = ErrorCode.message(); 273 raw_string_ostream OSS(Str); 274 if (!ErrCodeMsg.empty()) 275 OSS << ": " << ErrCodeMsg; 276 return OSS.str(); 277 } 278 return ""; 279 } 280 281 LockFileManager::~LockFileManager() { 282 if (getState() != LFS_Owned) 283 return; 284 285 // Since we own the lock, remove the lock file and our own unique lock file. 286 sys::fs::remove(LockFileName); 287 sys::fs::remove(UniqueLockFileName); 288 // The unique file is now gone, so remove it from the signal handler. This 289 // matches a sys::RemoveFileOnSignal() in LockFileManager(). 290 sys::DontRemoveFileOnSignal(UniqueLockFileName); 291 } 292 293 LockFileManager::WaitForUnlockResult 294 LockFileManager::waitForUnlock(const unsigned MaxSeconds) { 295 if (getState() != LFS_Shared) 296 return Res_Success; 297 298 #ifdef _WIN32 299 unsigned long Interval = 1; 300 #else 301 struct timespec Interval; 302 Interval.tv_sec = 0; 303 Interval.tv_nsec = 1000000; 304 #endif 305 do { 306 // Sleep for the designated interval, to allow the owning process time to 307 // finish up and remove the lock file. 308 // FIXME: Should we hook in to system APIs to get a notification when the 309 // lock file is deleted? 310 #ifdef _WIN32 311 Sleep(Interval); 312 #else 313 nanosleep(&Interval, nullptr); 314 #endif 315 316 if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) == 317 errc::no_such_file_or_directory) { 318 // If the original file wasn't created, somone thought the lock was dead. 319 if (!sys::fs::exists(FileName)) 320 return Res_OwnerDied; 321 return Res_Success; 322 } 323 324 // If the process owning the lock died without cleaning up, just bail out. 325 if (!processStillExecuting((*Owner).first, (*Owner).second)) 326 return Res_OwnerDied; 327 328 // Exponentially increase the time we wait for the lock to be removed. 329 #ifdef _WIN32 330 Interval *= 2; 331 #else 332 Interval.tv_sec *= 2; 333 Interval.tv_nsec *= 2; 334 if (Interval.tv_nsec >= 1000000000) { 335 ++Interval.tv_sec; 336 Interval.tv_nsec -= 1000000000; 337 } 338 #endif 339 } while ( 340 #ifdef _WIN32 341 Interval < MaxSeconds * 1000 342 #else 343 Interval.tv_sec < (time_t)MaxSeconds 344 #endif 345 ); 346 347 // Give up. 348 return Res_Timeout; 349 } 350 351 std::error_code LockFileManager::unsafeRemoveLockFile() { 352 return sys::fs::remove(LockFileName); 353 } 354