LLVM  12.0.0git
LockFileManager.h
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1 //===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 #ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H
9 #define LLVM_SUPPORT_LOCKFILEMANAGER_H
10 
11 #include "llvm/ADT/Optional.h"
12 #include "llvm/ADT/SmallString.h"
13 #include <system_error>
14 #include <utility> // for std::pair
15 
16 namespace llvm {
17 class StringRef;
18 
19 /// 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.
28 public:
29  /// Describes the state of a lock file.
31  /// The lock file has been created and is owned by this instance
32  /// of the object.
34  /// The lock file already exists and is owned by some other
35  /// instance.
37  /// An error occurred while trying to create or find the lock
38  /// file.
40  };
41 
42  /// Describes the result of waiting for the owner to release the lock.
44  /// The lock was released successfully.
46  /// Owner died while holding the lock.
48  /// Reached timeout while waiting for the owner to release the lock.
50  };
51 
52 private:
53  SmallString<128> FileName;
54  SmallString<128> LockFileName;
55  SmallString<128> UniqueLockFileName;
56 
58  std::error_code ErrorCode;
59  std::string ErrorDiagMsg;
60 
61  LockFileManager(const LockFileManager &) = delete;
62  LockFileManager &operator=(const LockFileManager &) = delete;
63 
65  readLockFile(StringRef LockFileName);
66 
67  static bool processStillExecuting(StringRef Hostname, int PID);
68 
69 public:
70 
71  LockFileManager(StringRef FileName);
73 
74  /// Determine the state of the lock file.
75  LockFileState getState() const;
76 
77  operator LockFileState() const { return getState(); }
78 
79  /// For a shared lock, wait until the owner releases the lock.
80  /// Total timeout for the file to appear is ~1.5 minutes.
81  /// \param MaxSeconds the maximum total wait time in seconds.
82  WaitForUnlockResult waitForUnlock(const unsigned MaxSeconds = 90);
83 
84  /// 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  /// Get error message, or "" if there is no error.
89  std::string getErrorMessage() const;
90 
91  /// 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
This class represents lattice values for constants.
Definition: AllocatorList.h:23
WaitForUnlockResult
Describes the result of waiting for the owner to release the lock.
std::string getErrorMessage() const
Get error message, or "" if there is no error.
The lock was released successfully.
void setError(const std::error_code &EC, StringRef ErrorMsg="")
Set error and error message.
An error occurred while trying to create or find the lock file.
std::error_code unsafeRemoveLockFile()
Remove the lock file.
LockFileState getState() const
Determine the state of the lock file.
LockFileState
Describes the state of a lock file.
Reached timeout while waiting for the owner to release the lock.
Owner died while holding the lock.
WaitForUnlockResult waitForUnlock(const unsigned MaxSeconds=90)
For a shared lock, wait until the owner releases the lock.
The lock file has been created and is owned by this instance of the object.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:57
Class that manages the creation of a lock file to aid implicit coordination between different process...
The lock file already exists and is owned by some other instance.