Andrew Scull | 5e1ddfa | 2018-08-14 10:06:54 +0100 | [diff] [blame^] | 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/Support/FileSystem.h" |
| 15 | #include <system_error> |
| 16 | #include <utility> // for std::pair |
| 17 | |
| 18 | namespace llvm { |
| 19 | class StringRef; |
| 20 | |
| 21 | /// \brief Class that manages the creation of a lock file to aid |
| 22 | /// implicit coordination between different processes. |
| 23 | /// |
| 24 | /// The implicit coordination works by creating a ".lock" file alongside |
| 25 | /// the file that we're coordinating for, using the atomicity of the file |
| 26 | /// system to ensure that only a single process can create that ".lock" file. |
| 27 | /// When the lock file is removed, the owning process has finished the |
| 28 | /// operation. |
| 29 | class LockFileManager { |
| 30 | public: |
| 31 | /// \brief Describes the state of a lock file. |
| 32 | enum LockFileState { |
| 33 | /// \brief The lock file has been created and is owned by this instance |
| 34 | /// of the object. |
| 35 | LFS_Owned, |
| 36 | /// \brief The lock file already exists and is owned by some other |
| 37 | /// instance. |
| 38 | LFS_Shared, |
| 39 | /// \brief An error occurred while trying to create or find the lock |
| 40 | /// file. |
| 41 | LFS_Error |
| 42 | }; |
| 43 | |
| 44 | /// \brief Describes the result of waiting for the owner to release the lock. |
| 45 | enum WaitForUnlockResult { |
| 46 | /// \brief The lock was released successfully. |
| 47 | Res_Success, |
| 48 | /// \brief Owner died while holding the lock. |
| 49 | Res_OwnerDied, |
| 50 | /// \brief Reached timeout while waiting for the owner to release the lock. |
| 51 | Res_Timeout |
| 52 | }; |
| 53 | |
| 54 | private: |
| 55 | SmallString<128> FileName; |
| 56 | SmallString<128> LockFileName; |
| 57 | Optional<sys::fs::TempFile> UniqueLockFile; |
| 58 | |
| 59 | Optional<std::pair<std::string, int> > Owner; |
| 60 | std::error_code ErrorCode; |
| 61 | std::string ErrorDiagMsg; |
| 62 | |
| 63 | LockFileManager(const LockFileManager &) = delete; |
| 64 | LockFileManager &operator=(const LockFileManager &) = delete; |
| 65 | |
| 66 | static Optional<std::pair<std::string, int> > |
| 67 | readLockFile(StringRef LockFileName); |
| 68 | |
| 69 | static bool processStillExecuting(StringRef Hostname, int PID); |
| 70 | |
| 71 | public: |
| 72 | |
| 73 | LockFileManager(StringRef FileName); |
| 74 | ~LockFileManager(); |
| 75 | |
| 76 | /// \brief Determine the state of the lock file. |
| 77 | LockFileState getState() const; |
| 78 | |
| 79 | operator LockFileState() const { return getState(); } |
| 80 | |
| 81 | /// \brief For a shared lock, wait until the owner releases the lock. |
| 82 | WaitForUnlockResult waitForUnlock(); |
| 83 | |
| 84 | /// \brief Remove the lock file. This may delete a different lock file than |
| 85 | /// the one previously read if there is a race. |
| 86 | std::error_code unsafeRemoveLockFile(); |
| 87 | |
| 88 | /// \brief Get error message, or "" if there is no error. |
| 89 | std::string getErrorMessage() const; |
| 90 | |
| 91 | /// \brief Set error and error message |
| 92 | void setError(const std::error_code &EC, StringRef ErrorMsg = "") { |
| 93 | ErrorCode = EC; |
| 94 | ErrorDiagMsg = ErrorMsg.str(); |
| 95 | } |
| 96 | }; |
| 97 | |
| 98 | } // end namespace llvm |
| 99 | |
| 100 | #endif // LLVM_SUPPORT_LOCKFILEMANAGER_H |