1234285Sdim//===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===// 2234285Sdim// 3353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4353358Sdim// See https://llvm.org/LICENSE.txt for license information. 5353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6234285Sdim// 7234285Sdim//===----------------------------------------------------------------------===// 8234285Sdim#ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H 9234285Sdim#define LLVM_SUPPORT_LOCKFILEMANAGER_H 10234285Sdim 11234285Sdim#include "llvm/ADT/Optional.h" 12234285Sdim#include "llvm/ADT/SmallString.h" 13276479Sdim#include <system_error> 14234285Sdim#include <utility> // for std::pair 15234285Sdim 16234285Sdimnamespace llvm { 17309124Sdimclass StringRef; 18309124Sdim 19341825Sdim/// Class that manages the creation of a lock file to aid 20234285Sdim/// implicit coordination between different processes. 21234285Sdim/// 22234285Sdim/// The implicit coordination works by creating a ".lock" file alongside 23234285Sdim/// the file that we're coordinating for, using the atomicity of the file 24234285Sdim/// system to ensure that only a single process can create that ".lock" file. 25234285Sdim/// When the lock file is removed, the owning process has finished the 26234285Sdim/// operation. 27234285Sdimclass LockFileManager { 28234285Sdimpublic: 29341825Sdim /// Describes the state of a lock file. 30234285Sdim enum LockFileState { 31341825Sdim /// The lock file has been created and is owned by this instance 32234285Sdim /// of the object. 33234285Sdim LFS_Owned, 34341825Sdim /// The lock file already exists and is owned by some other 35234285Sdim /// instance. 36234285Sdim LFS_Shared, 37341825Sdim /// An error occurred while trying to create or find the lock 38234285Sdim /// file. 39234285Sdim LFS_Error 40234285Sdim }; 41234285Sdim 42341825Sdim /// Describes the result of waiting for the owner to release the lock. 43276479Sdim enum WaitForUnlockResult { 44341825Sdim /// The lock was released successfully. 45276479Sdim Res_Success, 46341825Sdim /// Owner died while holding the lock. 47276479Sdim Res_OwnerDied, 48341825Sdim /// Reached timeout while waiting for the owner to release the lock. 49276479Sdim Res_Timeout 50276479Sdim }; 51276479Sdim 52234285Sdimprivate: 53249423Sdim SmallString<128> FileName; 54234285Sdim SmallString<128> LockFileName; 55341825Sdim SmallString<128> UniqueLockFileName; 56234285Sdim 57234285Sdim Optional<std::pair<std::string, int> > Owner; 58327952Sdim std::error_code ErrorCode; 59309124Sdim std::string ErrorDiagMsg; 60234285Sdim 61288943Sdim LockFileManager(const LockFileManager &) = delete; 62288943Sdim LockFileManager &operator=(const LockFileManager &) = delete; 63234285Sdim 64234285Sdim static Optional<std::pair<std::string, int> > 65234285Sdim readLockFile(StringRef LockFileName); 66234285Sdim 67234285Sdim static bool processStillExecuting(StringRef Hostname, int PID); 68234285Sdim 69234285Sdimpublic: 70234285Sdim 71234285Sdim LockFileManager(StringRef FileName); 72234285Sdim ~LockFileManager(); 73234285Sdim 74341825Sdim /// Determine the state of the lock file. 75234285Sdim LockFileState getState() const; 76234285Sdim 77234285Sdim operator LockFileState() const { return getState(); } 78234285Sdim 79341825Sdim /// For a shared lock, wait until the owner releases the lock. 80360784Sdim /// Total timeout for the file to appear is ~1.5 minutes. 81360784Sdim /// \param MaxSeconds the maximum wait time per iteration in seconds. 82360784Sdim WaitForUnlockResult waitForUnlock(const unsigned MaxSeconds = 40); 83288943Sdim 84341825Sdim /// Remove the lock file. This may delete a different lock file than 85288943Sdim /// the one previously read if there is a race. 86288943Sdim std::error_code unsafeRemoveLockFile(); 87309124Sdim 88341825Sdim /// Get error message, or "" if there is no error. 89309124Sdim std::string getErrorMessage() const; 90309124Sdim 91341825Sdim /// Set error and error message 92327952Sdim void setError(const std::error_code &EC, StringRef ErrorMsg = "") { 93327952Sdim ErrorCode = EC; 94309124Sdim ErrorDiagMsg = ErrorMsg.str(); 95309124Sdim } 96234285Sdim}; 97234285Sdim 98234285Sdim} // end namespace llvm 99234285Sdim 100234285Sdim#endif // LLVM_SUPPORT_LOCKFILEMANAGER_H 101