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/STLExtras.h" 11 #include "llvm/ADT/StringExtras.h" 12 #include "llvm/Support/Errc.h" 13 #include "llvm/Support/FileSystem.h" 14 #include "llvm/Support/MemoryBuffer.h" 15 #include "llvm/Support/Path.h" 16 #include "llvm/Support/raw_ostream.h" 17 #include <sys/stat.h> 18 #include <sys/types.h> 19 #if LLVM_ON_WIN32 20 #include <windows.h> 21 #endif 22 #if LLVM_ON_UNIX 23 #include <unistd.h> 24 #endif 25 using namespace llvm; 26 27 /// \brief Attempt to read the lock file with the given name, if it exists. 28 /// 29 /// \param LockFileName The name of the lock file to read. 30 /// 31 /// \returns The process ID of the process that owns this lock file 32 Optional<std::pair<std::string, int> > 33 LockFileManager::readLockFile(StringRef LockFileName) { 34 // Read the owning host and PID out of the lock file. If it appears that the 35 // owning process is dead, the lock file is invalid. 36 std::unique_ptr<MemoryBuffer> MB; 37 if (MemoryBuffer::getFile(LockFileName, MB)) { 38 sys::fs::remove(LockFileName); 39 return None; 40 } 41 42 StringRef Hostname; 43 StringRef PIDStr; 44 std::tie(Hostname, PIDStr) = getToken(MB->getBuffer(), " "); 45 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" ")); 46 int PID; 47 if (!PIDStr.getAsInteger(10, PID)) { 48 auto Owner = std::make_pair(std::string(Hostname), PID); 49 if (processStillExecuting(Owner.first, Owner.second)) 50 return Owner; 51 } 52 53 // Delete the lock file. It's invalid anyway. 54 sys::fs::remove(LockFileName); 55 return None; 56 } 57 58 bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) { 59 #if LLVM_ON_UNIX && !defined(__ANDROID__) 60 char MyHostname[256]; 61 MyHostname[255] = 0; 62 MyHostname[0] = 0; 63 gethostname(MyHostname, 255); 64 // Check whether the process is dead. If so, we're done. 65 if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH) 66 return false; 67 #endif 68 69 return true; 70 } 71 72 LockFileManager::LockFileManager(StringRef FileName) 73 { 74 this->FileName = FileName; 75 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) { 76 Error = EC; 77 return; 78 } 79 LockFileName = this->FileName; 80 LockFileName += ".lock"; 81 82 // If the lock file already exists, don't bother to try to create our own 83 // lock file; it won't work anyway. Just figure out who owns this lock file. 84 if ((Owner = readLockFile(LockFileName))) 85 return; 86 87 // Create a lock file that is unique to this instance. 88 UniqueLockFileName = LockFileName; 89 UniqueLockFileName += "-%%%%%%%%"; 90 int UniqueLockFileID; 91 if (std::error_code EC = sys::fs::createUniqueFile( 92 UniqueLockFileName.str(), UniqueLockFileID, UniqueLockFileName)) { 93 Error = EC; 94 return; 95 } 96 97 // Write our process ID to our unique lock file. 98 { 99 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true); 100 101 #if LLVM_ON_UNIX 102 // FIXME: move getpid() call into LLVM 103 char hostname[256]; 104 hostname[255] = 0; 105 hostname[0] = 0; 106 gethostname(hostname, 255); 107 Out << hostname << ' ' << getpid(); 108 #else 109 Out << "localhost 1"; 110 #endif 111 Out.close(); 112 113 if (Out.has_error()) { 114 // We failed to write out PID, so make up an excuse, remove the 115 // unique lock file, and fail. 116 Error = make_error_code(errc::no_space_on_device); 117 sys::fs::remove(UniqueLockFileName.c_str()); 118 return; 119 } 120 } 121 122 while (1) { 123 // Create a link from the lock file name. If this succeeds, we're done. 124 std::error_code EC = 125 sys::fs::create_link(UniqueLockFileName.str(), LockFileName.str()); 126 if (!EC) 127 return; 128 129 if (EC != errc::file_exists) { 130 Error = EC; 131 return; 132 } 133 134 // Someone else managed to create the lock file first. Read the process ID 135 // from the lock file. 136 if ((Owner = readLockFile(LockFileName))) { 137 // Wipe out our unique lock file (it's useless now) 138 sys::fs::remove(UniqueLockFileName.str()); 139 return; 140 } 141 142 if (!sys::fs::exists(LockFileName.str())) { 143 // The previous owner released the lock file before we could read it. 144 // Try to get ownership again. 145 continue; 146 } 147 148 // There is a lock file that nobody owns; try to clean it up and get 149 // ownership. 150 if ((EC = sys::fs::remove(LockFileName.str()))) { 151 Error = EC; 152 return; 153 } 154 } 155 } 156 157 LockFileManager::LockFileState LockFileManager::getState() const { 158 if (Owner) 159 return LFS_Shared; 160 161 if (Error) 162 return LFS_Error; 163 164 return LFS_Owned; 165 } 166 167 LockFileManager::~LockFileManager() { 168 if (getState() != LFS_Owned) 169 return; 170 171 // Since we own the lock, remove the lock file and our own unique lock file. 172 sys::fs::remove(LockFileName.str()); 173 sys::fs::remove(UniqueLockFileName.str()); 174 } 175 176 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() { 177 if (getState() != LFS_Shared) 178 return Res_Success; 179 180 #if LLVM_ON_WIN32 181 unsigned long Interval = 1; 182 #else 183 struct timespec Interval; 184 Interval.tv_sec = 0; 185 Interval.tv_nsec = 1000000; 186 #endif 187 // Don't wait more than five minutes for the file to appear. 188 unsigned MaxSeconds = 300; 189 bool LockFileGone = false; 190 do { 191 // Sleep for the designated interval, to allow the owning process time to 192 // finish up and remove the lock file. 193 // FIXME: Should we hook in to system APIs to get a notification when the 194 // lock file is deleted? 195 #if LLVM_ON_WIN32 196 Sleep(Interval); 197 #else 198 nanosleep(&Interval, nullptr); 199 #endif 200 bool LockFileJustDisappeared = false; 201 202 // If the lock file is still expected to be there, check whether it still 203 // is. 204 if (!LockFileGone) { 205 bool Exists; 206 if (!sys::fs::exists(LockFileName.str(), Exists) && !Exists) { 207 LockFileGone = true; 208 LockFileJustDisappeared = true; 209 } 210 } 211 212 // If the lock file is no longer there, check if the original file is 213 // available now. 214 if (LockFileGone) { 215 if (sys::fs::exists(FileName.str())) { 216 return Res_Success; 217 } 218 219 // The lock file is gone, so now we're waiting for the original file to 220 // show up. If this just happened, reset our waiting intervals and keep 221 // waiting. 222 if (LockFileJustDisappeared) { 223 MaxSeconds = 5; 224 225 #if LLVM_ON_WIN32 226 Interval = 1; 227 #else 228 Interval.tv_sec = 0; 229 Interval.tv_nsec = 1000000; 230 #endif 231 continue; 232 } 233 } 234 235 // If we're looking for the lock file to disappear, but the process 236 // owning the lock died without cleaning up, just bail out. 237 if (!LockFileGone && 238 !processStillExecuting((*Owner).first, (*Owner).second)) { 239 return Res_OwnerDied; 240 } 241 242 // Exponentially increase the time we wait for the lock to be removed. 243 #if LLVM_ON_WIN32 244 Interval *= 2; 245 #else 246 Interval.tv_sec *= 2; 247 Interval.tv_nsec *= 2; 248 if (Interval.tv_nsec >= 1000000000) { 249 ++Interval.tv_sec; 250 Interval.tv_nsec -= 1000000000; 251 } 252 #endif 253 } while ( 254 #if LLVM_ON_WIN32 255 Interval < MaxSeconds * 1000 256 #else 257 Interval.tv_sec < (time_t)MaxSeconds 258 #endif 259 ); 260 261 // Give up. 262 return Res_Timeout; 263 } 264