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 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 37 MemoryBuffer::getFile(LockFileName); 38 if (!MBOrErr) { 39 sys::fs::remove(LockFileName); 40 return None; 41 } 42 MemoryBuffer &MB = *MBOrErr.get(); 43 44 StringRef Hostname; 45 StringRef PIDStr; 46 std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " "); 47 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" ")); 48 int PID; 49 if (!PIDStr.getAsInteger(10, PID)) { 50 auto Owner = std::make_pair(std::string(Hostname), PID); 51 if (processStillExecuting(Owner.first, Owner.second)) 52 return Owner; 53 } 54 55 // Delete the lock file. It's invalid anyway. 56 sys::fs::remove(LockFileName); 57 return None; 58 } 59 60 bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) { 61 #if LLVM_ON_UNIX && !defined(__ANDROID__) 62 char MyHostname[256]; 63 MyHostname[255] = 0; 64 MyHostname[0] = 0; 65 gethostname(MyHostname, 255); 66 // Check whether the process is dead. If so, we're done. 67 if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH) 68 return false; 69 #endif 70 71 return true; 72 } 73 74 LockFileManager::LockFileManager(StringRef FileName) 75 { 76 this->FileName = FileName; 77 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) { 78 Error = EC; 79 return; 80 } 81 LockFileName = this->FileName; 82 LockFileName += ".lock"; 83 84 // If the lock file already exists, don't bother to try to create our own 85 // lock file; it won't work anyway. Just figure out who owns this lock file. 86 if ((Owner = readLockFile(LockFileName))) 87 return; 88 89 // Create a lock file that is unique to this instance. 90 UniqueLockFileName = LockFileName; 91 UniqueLockFileName += "-%%%%%%%%"; 92 int UniqueLockFileID; 93 if (std::error_code EC = sys::fs::createUniqueFile( 94 UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) { 95 Error = EC; 96 return; 97 } 98 99 // Write our process ID to our unique lock file. 100 { 101 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true); 102 103 #if LLVM_ON_UNIX 104 // FIXME: move getpid() call into LLVM 105 char hostname[256]; 106 hostname[255] = 0; 107 hostname[0] = 0; 108 gethostname(hostname, 255); 109 Out << hostname << ' ' << getpid(); 110 #else 111 Out << "localhost 1"; 112 #endif 113 Out.close(); 114 115 if (Out.has_error()) { 116 // We failed to write out PID, so make up an excuse, remove the 117 // unique lock file, and fail. 118 Error = make_error_code(errc::no_space_on_device); 119 sys::fs::remove(UniqueLockFileName); 120 return; 121 } 122 } 123 124 while (1) { 125 // Create a link from the lock file name. If this succeeds, we're done. 126 std::error_code EC = 127 sys::fs::create_link(UniqueLockFileName, LockFileName); 128 if (!EC) 129 return; 130 131 if (EC != errc::file_exists) { 132 Error = EC; 133 return; 134 } 135 136 // Someone else managed to create the lock file first. Read the process ID 137 // from the lock file. 138 if ((Owner = readLockFile(LockFileName))) { 139 // Wipe out our unique lock file (it's useless now) 140 sys::fs::remove(UniqueLockFileName); 141 return; 142 } 143 144 if (!sys::fs::exists(LockFileName)) { 145 // The previous owner released the lock file before we could read it. 146 // Try to get ownership again. 147 continue; 148 } 149 150 // There is a lock file that nobody owns; try to clean it up and get 151 // ownership. 152 if ((EC = sys::fs::remove(LockFileName))) { 153 Error = EC; 154 return; 155 } 156 } 157 } 158 159 LockFileManager::LockFileState LockFileManager::getState() const { 160 if (Owner) 161 return LFS_Shared; 162 163 if (Error) 164 return LFS_Error; 165 166 return LFS_Owned; 167 } 168 169 LockFileManager::~LockFileManager() { 170 if (getState() != LFS_Owned) 171 return; 172 173 // Since we own the lock, remove the lock file and our own unique lock file. 174 sys::fs::remove(LockFileName); 175 sys::fs::remove(UniqueLockFileName); 176 } 177 178 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() { 179 if (getState() != LFS_Shared) 180 return Res_Success; 181 182 #if LLVM_ON_WIN32 183 unsigned long Interval = 1; 184 #else 185 struct timespec Interval; 186 Interval.tv_sec = 0; 187 Interval.tv_nsec = 1000000; 188 #endif 189 // Don't wait more than five minutes per iteration. Total timeout for the file 190 // to appear is ~8.5 mins. 191 const unsigned MaxSeconds = 5*60; 192 do { 193 // Sleep for the designated interval, to allow the owning process time to 194 // finish up and remove the lock file. 195 // FIXME: Should we hook in to system APIs to get a notification when the 196 // lock file is deleted? 197 #if LLVM_ON_WIN32 198 Sleep(Interval); 199 #else 200 nanosleep(&Interval, nullptr); 201 #endif 202 203 if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) == 204 errc::no_such_file_or_directory) { 205 // If the original file wasn't created, somone thought the lock was dead. 206 if (!sys::fs::exists(FileName)) 207 return Res_OwnerDied; 208 return Res_Success; 209 } 210 211 // If the process owning the lock died without cleaning up, just bail out. 212 if (!processStillExecuting((*Owner).first, (*Owner).second)) 213 return Res_OwnerDied; 214 215 // Exponentially increase the time we wait for the lock to be removed. 216 #if LLVM_ON_WIN32 217 Interval *= 2; 218 #else 219 Interval.tv_sec *= 2; 220 Interval.tv_nsec *= 2; 221 if (Interval.tv_nsec >= 1000000000) { 222 ++Interval.tv_sec; 223 Interval.tv_nsec -= 1000000000; 224 } 225 #endif 226 } while ( 227 #if LLVM_ON_WIN32 228 Interval < MaxSeconds * 1000 229 #else 230 Interval.tv_sec < (time_t)MaxSeconds 231 #endif 232 ); 233 234 // Give up. 235 return Res_Timeout; 236 } 237 238 std::error_code LockFileManager::unsafeRemoveLockFile() { 239 return sys::fs::remove(LockFileName); 240 } 241