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/Support/FileSystem.h" 11#include "llvm/Support/raw_ostream.h" 12#include <fstream> 13#include <sys/types.h> 14#include <sys/stat.h> 15#if LLVM_ON_WIN32 16#include <windows.h> 17#endif 18#if LLVM_ON_UNIX 19#include <unistd.h> 20#endif 21using namespace llvm; 22 23/// \brief Attempt to read the lock file with the given name, if it exists. 24/// 25/// \param LockFileName The name of the lock file to read. 26/// 27/// \returns The process ID of the process that owns this lock file 28Optional<std::pair<std::string, int> > 29LockFileManager::readLockFile(StringRef LockFileName) { 30 // Check whether the lock file exists. If not, clearly there's nothing 31 // to read, so we just return. 32 bool Exists = false; 33 if (sys::fs::exists(LockFileName, Exists) || !Exists) 34 return Optional<std::pair<std::string, int> >(); 35 36 // Read the owning host and PID out of the lock file. If it appears that the 37 // owning process is dead, the lock file is invalid. 38 int PID = 0; 39 std::string Hostname; 40 std::ifstream Input(LockFileName.str().c_str()); 41 if (Input >> Hostname >> PID && PID > 0 && 42 processStillExecuting(Hostname, PID)) 43 return std::make_pair(Hostname, PID); 44 45 // Delete the lock file. It's invalid anyway. 46 bool Existed; 47 sys::fs::remove(LockFileName, Existed); 48 return Optional<std::pair<std::string, int> >(); 49} 50 51bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) { 52#if LLVM_ON_UNIX && !defined(__ANDROID__) 53 char MyHostname[256]; 54 MyHostname[255] = 0; 55 MyHostname[0] = 0; 56 gethostname(MyHostname, 255); 57 // Check whether the process is dead. If so, we're done. 58 if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH) 59 return false; 60#endif 61 62 return true; 63} 64 65LockFileManager::LockFileManager(StringRef FileName) 66{ 67 LockFileName = FileName; 68 LockFileName += ".lock"; 69 70 // If the lock file already exists, don't bother to try to create our own 71 // lock file; it won't work anyway. Just figure out who owns this lock file. 72 if ((Owner = readLockFile(LockFileName))) 73 return; 74 75 // Create a lock file that is unique to this instance. 76 UniqueLockFileName = LockFileName; 77 UniqueLockFileName += "-%%%%%%%%"; 78 int UniqueLockFileID; 79 if (error_code EC 80 = sys::fs::unique_file(UniqueLockFileName.str(), 81 UniqueLockFileID, 82 UniqueLockFileName, 83 /*makeAbsolute=*/false)) { 84 Error = EC; 85 return; 86 } 87 88 // Write our process ID to our unique lock file. 89 { 90 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true); 91 92#if LLVM_ON_UNIX 93 // FIXME: move getpid() call into LLVM 94 char hostname[256]; 95 hostname[255] = 0; 96 hostname[0] = 0; 97 gethostname(hostname, 255); 98 Out << hostname << ' ' << getpid(); 99#else 100 Out << "localhost 1"; 101#endif 102 Out.close(); 103 104 if (Out.has_error()) { 105 // We failed to write out PID, so make up an excuse, remove the 106 // unique lock file, and fail. 107 Error = make_error_code(errc::no_space_on_device); 108 bool Existed; 109 sys::fs::remove(UniqueLockFileName.c_str(), Existed); 110 return; 111 } 112 } 113 114 // Create a hard link from the lock file name. If this succeeds, we're done. 115 error_code EC 116 = sys::fs::create_hard_link(UniqueLockFileName.str(), 117 LockFileName.str()); 118 if (EC == errc::success) 119 return; 120 121 // Creating the hard link failed. 122 123#ifdef LLVM_ON_UNIX 124 // The creation of the hard link may appear to fail, but if stat'ing the 125 // unique file returns a link count of 2, then we can still declare success. 126 struct stat StatBuf; 127 if (stat(UniqueLockFileName.c_str(), &StatBuf) == 0 && 128 StatBuf.st_nlink == 2) 129 return; 130#endif 131 132 // Someone else managed to create the lock file first. Wipe out our unique 133 // lock file (it's useless now) and read the process ID from the lock file. 134 bool Existed; 135 sys::fs::remove(UniqueLockFileName.str(), Existed); 136 if ((Owner = readLockFile(LockFileName))) 137 return; 138 139 // There is a lock file that nobody owns; try to clean it up and report 140 // an error. 141 sys::fs::remove(LockFileName.str(), Existed); 142 Error = EC; 143} 144 145LockFileManager::LockFileState LockFileManager::getState() const { 146 if (Owner) 147 return LFS_Shared; 148 149 if (Error) 150 return LFS_Error; 151 152 return LFS_Owned; 153} 154 155LockFileManager::~LockFileManager() { 156 if (getState() != LFS_Owned) 157 return; 158 159 // Since we own the lock, remove the lock file and our own unique lock file. 160 bool Existed; 161 sys::fs::remove(LockFileName.str(), Existed); 162 sys::fs::remove(UniqueLockFileName.str(), Existed); 163} 164 165void LockFileManager::waitForUnlock() { 166 if (getState() != LFS_Shared) 167 return; 168 169#if LLVM_ON_WIN32 170 unsigned long Interval = 1; 171#else 172 struct timespec Interval; 173 Interval.tv_sec = 0; 174 Interval.tv_nsec = 1000000; 175#endif 176 // Don't wait more than an hour for the file to appear. 177 const unsigned MaxSeconds = 3600; 178 do { 179 // Sleep for the designated interval, to allow the owning process time to 180 // finish up and remove the lock file. 181 // FIXME: Should we hook in to system APIs to get a notification when the 182 // lock file is deleted? 183#if LLVM_ON_WIN32 184 Sleep(Interval); 185#else 186 nanosleep(&Interval, NULL); 187#endif 188 // If the file no longer exists, we're done. 189 bool Exists = false; 190 if (!sys::fs::exists(LockFileName.str(), Exists) && !Exists) 191 return; 192 193 if (!processStillExecuting((*Owner).first, (*Owner).second)) 194 return; 195 196 // Exponentially increase the time we wait for the lock to be removed. 197#if LLVM_ON_WIN32 198 Interval *= 2; 199#else 200 Interval.tv_sec *= 2; 201 Interval.tv_nsec *= 2; 202 if (Interval.tv_nsec >= 1000000000) { 203 ++Interval.tv_sec; 204 Interval.tv_nsec -= 1000000000; 205 } 206#endif 207 } while ( 208#if LLVM_ON_WIN32 209 Interval < MaxSeconds * 1000 210#else 211 Interval.tv_sec < (time_t)MaxSeconds 212#endif 213 ); 214 215 // Give up. 216} 217