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 <system_error> 16 #include <utility> // for std::pair 17 18 namespace llvm { 19 /// \brief Class that manages the creation of a lock file to aid 20 /// implicit coordination between different processes. 21 /// 22 /// The implicit coordination works by creating a ".lock" file alongside 23 /// the file that we're coordinating for, using the atomicity of the file 24 /// system to ensure that only a single process can create that ".lock" file. 25 /// When the lock file is removed, the owning process has finished the 26 /// operation. 27 class LockFileManager { 28 public: 29 /// \brief Describes the state of a lock file. 30 enum LockFileState { 31 /// \brief The lock file has been created and is owned by this instance 32 /// of the object. 33 LFS_Owned, 34 /// \brief The lock file already exists and is owned by some other 35 /// instance. 36 LFS_Shared, 37 /// \brief An error occurred while trying to create or find the lock 38 /// file. 39 LFS_Error 40 }; 41 42 /// \brief Describes the result of waiting for the owner to release the lock. 43 enum WaitForUnlockResult { 44 /// \brief The lock was released successfully. 45 Res_Success, 46 /// \brief Owner died while holding the lock. 47 Res_OwnerDied, 48 /// \brief Reached timeout while waiting for the owner to release the lock. 49 Res_Timeout 50 }; 51 52 private: 53 SmallString<128> FileName; 54 SmallString<128> LockFileName; 55 SmallString<128> UniqueLockFileName; 56 57 Optional<std::pair<std::string, int> > Owner; 58 Optional<std::error_code> Error; 59 60 LockFileManager(const LockFileManager &) = delete; 61 LockFileManager &operator=(const LockFileManager &) = delete; 62 63 static Optional<std::pair<std::string, int> > 64 readLockFile(StringRef LockFileName); 65 66 static bool processStillExecuting(StringRef Hostname, int PID); 67 68 public: 69 70 LockFileManager(StringRef FileName); 71 ~LockFileManager(); 72 73 /// \brief Determine the state of the lock file. 74 LockFileState getState() const; 75 LockFileState()76 operator LockFileState() const { return getState(); } 77 78 /// \brief For a shared lock, wait until the owner releases the lock. 79 WaitForUnlockResult waitForUnlock(); 80 81 /// \brief Remove the lock file. This may delete a different lock file than 82 /// the one previously read if there is a race. 83 std::error_code unsafeRemoveLockFile(); 84 }; 85 86 } // end namespace llvm 87 88 #endif // LLVM_SUPPORT_LOCKFILEMANAGER_H 89