1 //===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===// 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 #ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H 10 #define LLVM_SUPPORT_LOCKFILEMANAGER_H 11 12 #include "llvm/ADT/Optional.h" 13 #include "llvm/ADT/SmallString.h" 14 #include "llvm/ADT/StringRef.h" 15 #include "llvm/Support/system_error.h" 16 #include <utility> // for std::pair 17 18 namespace llvm { 19 20 /// \brief Class that manages the creation of a lock file to aid 21 /// implicit coordination between different processes. 22 /// 23 /// The implicit coordination works by creating a ".lock" file alongside 24 /// the file that we're coordinating for, using the atomicity of the file 25 /// system to ensure that only a single process can create that ".lock" file. 26 /// When the lock file is removed, the owning process has finished the 27 /// operation. 28 class LockFileManager { 29 public: 30 /// \brief Describes the state of a lock file. 31 enum LockFileState { 32 /// \brief The lock file has been created and is owned by this instance 33 /// of the object. 34 LFS_Owned, 35 /// \brief The lock file already exists and is owned by some other 36 /// instance. 37 LFS_Shared, 38 /// \brief An error occurred while trying to create or find the lock 39 /// file. 40 LFS_Error 41 }; 42 43 private: 44 SmallString<128> FileName; 45 SmallString<128> LockFileName; 46 SmallString<128> UniqueLockFileName; 47 48 Optional<std::pair<std::string, int> > Owner; 49 Optional<error_code> Error; 50 51 LockFileManager(const LockFileManager &) LLVM_DELETED_FUNCTION; 52 LockFileManager &operator=(const LockFileManager &) LLVM_DELETED_FUNCTION; 53 54 static Optional<std::pair<std::string, int> > 55 readLockFile(StringRef LockFileName); 56 57 static bool processStillExecuting(StringRef Hostname, int PID); 58 59 public: 60 61 LockFileManager(StringRef FileName); 62 ~LockFileManager(); 63 64 /// \brief Determine the state of the lock file. 65 LockFileState getState() const; 66 67 operator LockFileState() const { return getState(); } 68 69 /// \brief For a shared lock, wait until the owner releases the lock. 70 void waitForUnlock(); 71 }; 72 73 } // end namespace llvm 74 75 #endif // LLVM_SUPPORT_LOCKFILEMANAGER_H 76
