101 lines
3.1 KiB
C
101 lines
3.1 KiB
C
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//===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H
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#define LLVM_SUPPORT_LOCKFILEMANAGER_H
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/SmallString.h"
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#include <system_error>
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#include <utility> // for std::pair
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namespace llvm {
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class StringRef;
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/// Class that manages the creation of a lock file to aid
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/// implicit coordination between different processes.
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///
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/// The implicit coordination works by creating a ".lock" file alongside
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/// the file that we're coordinating for, using the atomicity of the file
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/// system to ensure that only a single process can create that ".lock" file.
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/// When the lock file is removed, the owning process has finished the
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/// operation.
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class LockFileManager {
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public:
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/// Describes the state of a lock file.
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enum LockFileState {
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/// The lock file has been created and is owned by this instance
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/// of the object.
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LFS_Owned,
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/// The lock file already exists and is owned by some other
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/// instance.
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LFS_Shared,
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/// An error occurred while trying to create or find the lock
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/// file.
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LFS_Error
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};
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/// Describes the result of waiting for the owner to release the lock.
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enum WaitForUnlockResult {
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/// The lock was released successfully.
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Res_Success,
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/// Owner died while holding the lock.
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Res_OwnerDied,
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/// Reached timeout while waiting for the owner to release the lock.
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Res_Timeout
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};
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private:
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SmallString<128> FileName;
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SmallString<128> LockFileName;
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SmallString<128> UniqueLockFileName;
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Optional<std::pair<std::string, int> > Owner;
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std::error_code ErrorCode;
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std::string ErrorDiagMsg;
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LockFileManager(const LockFileManager &) = delete;
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LockFileManager &operator=(const LockFileManager &) = delete;
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static Optional<std::pair<std::string, int> >
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readLockFile(StringRef LockFileName);
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static bool processStillExecuting(StringRef Hostname, int PID);
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public:
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LockFileManager(StringRef FileName);
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~LockFileManager();
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/// Determine the state of the lock file.
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LockFileState getState() const;
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operator LockFileState() const { return getState(); }
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/// For a shared lock, wait until the owner releases the lock.
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/// Total timeout for the file to appear is ~1.5 minutes.
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/// \param MaxSeconds the maximum total wait time in seconds.
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WaitForUnlockResult waitForUnlock(const unsigned MaxSeconds = 90);
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/// Remove the lock file. This may delete a different lock file than
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/// the one previously read if there is a race.
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std::error_code unsafeRemoveLockFile();
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/// Get error message, or "" if there is no error.
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std::string getErrorMessage() const;
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/// Set error and error message
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void setError(const std::error_code &EC, StringRef ErrorMsg = "") {
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ErrorCode = EC;
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ErrorDiagMsg = ErrorMsg.str();
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}
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};
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} // end namespace llvm
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#endif // LLVM_SUPPORT_LOCKFILEMANAGER_H
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