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| 14 | pmbaty | 1 | //===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | #ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H |
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| 9 | #define LLVM_SUPPORT_LOCKFILEMANAGER_H |
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| 10 | |||
| 11 | #include "llvm/ADT/SmallString.h" |
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| 12 | #include <optional> |
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| 13 | #include <system_error> |
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| 14 | #include <utility> // for std::pair |
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| 15 | |||
| 16 | namespace llvm { |
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| 17 | class StringRef; |
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| 18 | |||
| 19 | /// Class that manages the creation of a lock file to aid |
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| 20 | /// implicit coordination between different processes. |
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| 21 | /// |
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| 22 | /// The implicit coordination works by creating a ".lock" file alongside |
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| 23 | /// the file that we're coordinating for, using the atomicity of the file |
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| 24 | /// system to ensure that only a single process can create that ".lock" file. |
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| 25 | /// When the lock file is removed, the owning process has finished the |
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| 26 | /// operation. |
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| 27 | class LockFileManager { |
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| 28 | public: |
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| 29 | /// Describes the state of a lock file. |
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| 30 | enum LockFileState { |
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| 31 | /// The lock file has been created and is owned by this instance |
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| 32 | /// of the object. |
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| 33 | LFS_Owned, |
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| 34 | /// The lock file already exists and is owned by some other |
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| 35 | /// instance. |
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| 36 | LFS_Shared, |
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| 37 | /// An error occurred while trying to create or find the lock |
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| 38 | /// file. |
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| 39 | LFS_Error |
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| 40 | }; |
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| 41 | |||
| 42 | /// Describes the result of waiting for the owner to release the lock. |
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| 43 | enum WaitForUnlockResult { |
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| 44 | /// The lock was released successfully. |
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| 45 | Res_Success, |
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| 46 | /// Owner died while holding the lock. |
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| 47 | Res_OwnerDied, |
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| 48 | /// Reached timeout while waiting for the owner to release the lock. |
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| 49 | Res_Timeout |
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| 50 | }; |
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| 51 | |||
| 52 | private: |
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| 53 | SmallString<128> FileName; |
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| 54 | SmallString<128> LockFileName; |
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| 55 | SmallString<128> UniqueLockFileName; |
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| 56 | |||
| 57 | std::optional<std::pair<std::string, int>> Owner; |
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| 58 | std::error_code ErrorCode; |
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| 59 | std::string ErrorDiagMsg; |
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| 60 | |||
| 61 | LockFileManager(const LockFileManager &) = delete; |
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| 62 | LockFileManager &operator=(const LockFileManager &) = delete; |
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| 63 | |||
| 64 | static std::optional<std::pair<std::string, int>> |
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| 65 | readLockFile(StringRef LockFileName); |
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| 66 | |||
| 67 | static bool processStillExecuting(StringRef Hostname, int PID); |
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| 68 | |||
| 69 | public: |
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| 70 | |||
| 71 | LockFileManager(StringRef FileName); |
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| 72 | ~LockFileManager(); |
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| 73 | |||
| 74 | /// Determine the state of the lock file. |
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| 75 | LockFileState getState() const; |
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| 76 | |||
| 77 | operator LockFileState() const { return getState(); } |
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| 78 | |||
| 79 | /// For a shared lock, wait until the owner releases the lock. |
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| 80 | /// Total timeout for the file to appear is ~1.5 minutes. |
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| 81 | /// \param MaxSeconds the maximum total wait time in seconds. |
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| 82 | WaitForUnlockResult waitForUnlock(const unsigned MaxSeconds = 90); |
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| 83 | |||
| 84 | /// Remove the lock file. This may delete a different lock file than |
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| 85 | /// the one previously read if there is a race. |
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| 86 | std::error_code unsafeRemoveLockFile(); |
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| 87 | |||
| 88 | /// Get error message, or "" if there is no error. |
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| 89 | std::string getErrorMessage() const; |
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| 90 | |||
| 91 | /// Set error and error message |
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| 92 | void setError(const std::error_code &EC, StringRef ErrorMsg = "") { |
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| 93 | ErrorCode = EC; |
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| 94 | ErrorDiagMsg = ErrorMsg.str(); |
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| 95 | } |
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| 96 | }; |
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| 97 | |||
| 98 | } // end namespace llvm |
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| 99 | |||
| 100 | #endif // LLVM_SUPPORT_LOCKFILEMANAGER_H |