1 //===--- LockFileManager.cpp - File-level Locking Utility------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 #include "llvm/Support/LockFileManager.h" 10 #include "llvm/ADT/StringExtras.h" 11 #include "llvm/Support/Errc.h" 12 #include "llvm/Support/FileSystem.h" 13 #include "llvm/Support/MemoryBuffer.h" 14 #include "llvm/Support/raw_ostream.h" 15 #include "llvm/Support/Signals.h" 16 #include <sys/stat.h> 17 #include <sys/types.h> 18 #if LLVM_ON_WIN32 19 #include <windows.h> 20 #endif 21 #if LLVM_ON_UNIX 22 #include <unistd.h> 23 #endif 24 25 #if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050) 26 #define USE_OSX_GETHOSTUUID 1 27 #else 28 #define USE_OSX_GETHOSTUUID 0 29 #endif 30 31 #if USE_OSX_GETHOSTUUID 32 #include <uuid/uuid.h> 33 #endif 34 using namespace llvm; 35 36 /// \brief Attempt to read the lock file with the given name, if it exists. 37 /// 38 /// \param LockFileName The name of the lock file to read. 39 /// 40 /// \returns The process ID of the process that owns this lock file 41 Optional<std::pair<std::string, int> > 42 LockFileManager::readLockFile(StringRef LockFileName) { 43 // Read the owning host and PID out of the lock file. If it appears that the 44 // owning process is dead, the lock file is invalid. 45 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 46 MemoryBuffer::getFile(LockFileName); 47 if (!MBOrErr) { 48 sys::fs::remove(LockFileName); 49 return None; 50 } 51 MemoryBuffer &MB = *MBOrErr.get(); 52 53 StringRef Hostname; 54 StringRef PIDStr; 55 std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " "); 56 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" ")); 57 int PID; 58 if (!PIDStr.getAsInteger(10, PID)) { 59 auto Owner = std::make_pair(std::string(Hostname), PID); 60 if (processStillExecuting(Owner.first, Owner.second)) 61 return Owner; 62 } 63 64 // Delete the lock file. It's invalid anyway. 65 sys::fs::remove(LockFileName); 66 return None; 67 } 68 69 static std::error_code getHostID(SmallVectorImpl<char> &HostID) { 70 HostID.clear(); 71 72 #if USE_OSX_GETHOSTUUID 73 // On OS X, use the more stable hardware UUID instead of hostname. 74 struct timespec wait = {1, 0}; // 1 second. 75 uuid_t uuid; 76 if (gethostuuid(uuid, &wait) != 0) 77 return std::error_code(errno, std::system_category()); 78 79 uuid_string_t UUIDStr; 80 uuid_unparse(uuid, UUIDStr); 81 StringRef UUIDRef(UUIDStr); 82 HostID.append(UUIDRef.begin(), UUIDRef.end()); 83 84 #elif LLVM_ON_UNIX 85 char HostName[256]; 86 HostName[255] = 0; 87 HostName[0] = 0; 88 gethostname(HostName, 255); 89 StringRef HostNameRef(HostName); 90 HostID.append(HostNameRef.begin(), HostNameRef.end()); 91 92 #else 93 StringRef Dummy("localhost"); 94 HostID.append(Dummy.begin(), Dummy.end()); 95 #endif 96 97 return std::error_code(); 98 } 99 100 bool LockFileManager::processStillExecuting(StringRef HostID, int PID) { 101 #if LLVM_ON_UNIX && !defined(__ANDROID__) 102 SmallString<256> StoredHostID; 103 if (getHostID(StoredHostID)) 104 return true; // Conservatively assume it's executing on error. 105 106 // Check whether the process is dead. If so, we're done. 107 if (StoredHostID == HostID && getsid(PID) == -1 && errno == ESRCH) 108 return false; 109 #endif 110 111 return true; 112 } 113 114 namespace { 115 /// An RAII helper object ensure that the unique lock file is removed. 116 /// 117 /// Ensures that if there is an error or a signal before we finish acquiring the 118 /// lock, the unique file will be removed. And if we successfully take the lock, 119 /// the signal handler is left in place so that signals while the lock is held 120 /// will remove the unique lock file. The caller should ensure there is a 121 /// matching call to sys::DontRemoveFileOnSignal when the lock is released. 122 class RemoveUniqueLockFileOnSignal { 123 StringRef Filename; 124 bool RemoveImmediately; 125 public: 126 RemoveUniqueLockFileOnSignal(StringRef Name) 127 : Filename(Name), RemoveImmediately(true) { 128 sys::RemoveFileOnSignal(Filename, nullptr); 129 } 130 ~RemoveUniqueLockFileOnSignal() { 131 if (!RemoveImmediately) { 132 // Leave the signal handler enabled. It will be removed when the lock is 133 // released. 134 return; 135 } 136 sys::fs::remove(Filename); 137 sys::DontRemoveFileOnSignal(Filename); 138 } 139 void lockAcquired() { RemoveImmediately = false; } 140 }; 141 } // end anonymous namespace 142 143 LockFileManager::LockFileManager(StringRef FileName) 144 { 145 this->FileName = FileName; 146 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) { 147 Error = EC; 148 return; 149 } 150 LockFileName = this->FileName; 151 LockFileName += ".lock"; 152 153 // If the lock file already exists, don't bother to try to create our own 154 // lock file; it won't work anyway. Just figure out who owns this lock file. 155 if ((Owner = readLockFile(LockFileName))) 156 return; 157 158 // Create a lock file that is unique to this instance. 159 UniqueLockFileName = LockFileName; 160 UniqueLockFileName += "-%%%%%%%%"; 161 int UniqueLockFileID; 162 if (std::error_code EC = sys::fs::createUniqueFile( 163 UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) { 164 Error = EC; 165 return; 166 } 167 168 // Write our process ID to our unique lock file. 169 { 170 SmallString<256> HostID; 171 if (auto EC = getHostID(HostID)) { 172 Error = EC; 173 return; 174 } 175 176 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true); 177 Out << HostID << ' '; 178 #if LLVM_ON_UNIX 179 Out << getpid(); 180 #else 181 Out << "1"; 182 #endif 183 Out.close(); 184 185 if (Out.has_error()) { 186 // We failed to write out PID, so make up an excuse, remove the 187 // unique lock file, and fail. 188 Error = make_error_code(errc::no_space_on_device); 189 sys::fs::remove(UniqueLockFileName); 190 return; 191 } 192 } 193 194 // Clean up the unique file on signal, which also releases the lock if it is 195 // held since the .lock symlink will point to a nonexistent file. 196 RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName); 197 198 while (1) { 199 // Create a link from the lock file name. If this succeeds, we're done. 200 std::error_code EC = 201 sys::fs::create_link(UniqueLockFileName, LockFileName); 202 if (!EC) { 203 RemoveUniqueFile.lockAcquired(); 204 return; 205 } 206 207 if (EC != errc::file_exists) { 208 Error = EC; 209 return; 210 } 211 212 // Someone else managed to create the lock file first. Read the process ID 213 // from the lock file. 214 if ((Owner = readLockFile(LockFileName))) { 215 // Wipe out our unique lock file (it's useless now) 216 sys::fs::remove(UniqueLockFileName); 217 return; 218 } 219 220 if (!sys::fs::exists(LockFileName)) { 221 // The previous owner released the lock file before we could read it. 222 // Try to get ownership again. 223 continue; 224 } 225 226 // There is a lock file that nobody owns; try to clean it up and get 227 // ownership. 228 if ((EC = sys::fs::remove(LockFileName))) { 229 Error = EC; 230 return; 231 } 232 } 233 } 234 235 LockFileManager::LockFileState LockFileManager::getState() const { 236 if (Owner) 237 return LFS_Shared; 238 239 if (Error) 240 return LFS_Error; 241 242 return LFS_Owned; 243 } 244 245 LockFileManager::~LockFileManager() { 246 if (getState() != LFS_Owned) 247 return; 248 249 // Since we own the lock, remove the lock file and our own unique lock file. 250 sys::fs::remove(LockFileName); 251 sys::fs::remove(UniqueLockFileName); 252 // The unique file is now gone, so remove it from the signal handler. This 253 // matches a sys::RemoveFileOnSignal() in LockFileManager(). 254 sys::DontRemoveFileOnSignal(UniqueLockFileName); 255 } 256 257 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() { 258 if (getState() != LFS_Shared) 259 return Res_Success; 260 261 #if LLVM_ON_WIN32 262 unsigned long Interval = 1; 263 #else 264 struct timespec Interval; 265 Interval.tv_sec = 0; 266 Interval.tv_nsec = 1000000; 267 #endif 268 // Don't wait more than five minutes per iteration. Total timeout for the file 269 // to appear is ~8.5 mins. 270 const unsigned MaxSeconds = 5*60; 271 do { 272 // Sleep for the designated interval, to allow the owning process time to 273 // finish up and remove the lock file. 274 // FIXME: Should we hook in to system APIs to get a notification when the 275 // lock file is deleted? 276 #if LLVM_ON_WIN32 277 Sleep(Interval); 278 #else 279 nanosleep(&Interval, nullptr); 280 #endif 281 282 if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) == 283 errc::no_such_file_or_directory) { 284 // If the original file wasn't created, somone thought the lock was dead. 285 if (!sys::fs::exists(FileName)) 286 return Res_OwnerDied; 287 return Res_Success; 288 } 289 290 // If the process owning the lock died without cleaning up, just bail out. 291 if (!processStillExecuting((*Owner).first, (*Owner).second)) 292 return Res_OwnerDied; 293 294 // Exponentially increase the time we wait for the lock to be removed. 295 #if LLVM_ON_WIN32 296 Interval *= 2; 297 #else 298 Interval.tv_sec *= 2; 299 Interval.tv_nsec *= 2; 300 if (Interval.tv_nsec >= 1000000000) { 301 ++Interval.tv_sec; 302 Interval.tv_nsec -= 1000000000; 303 } 304 #endif 305 } while ( 306 #if LLVM_ON_WIN32 307 Interval < MaxSeconds * 1000 308 #else 309 Interval.tv_sec < (time_t)MaxSeconds 310 #endif 311 ); 312 313 // Give up. 314 return Res_Timeout; 315 } 316 317 std::error_code LockFileManager::unsafeRemoveLockFile() { 318 return sys::fs::remove(LockFileName); 319 } 320
