Line data    Source code

       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 <system_error>
      15             : #include <utility> // for std::pair
      16             : 
      17             : namespace llvm {
      18             : class StringRef;
      19             : 
      20             : /// Class that manages the creation of a lock file to aid
      21             : /// implicit coordination between different processes.
      22             : ///
      23             : /// The implicit coordination works by creating a ".lock" file alongside
      24             : /// the file that we're coordinating for, using the atomicity of the file
      25             : /// system to ensure that only a single process can create that ".lock" file.
      26             : /// When the lock file is removed, the owning process has finished the
      27             : /// operation.
      28             : class LockFileManager {
      29             : public:
      30             :   /// Describes the state of a lock file.
      31             :   enum LockFileState {
      32             :     /// The lock file has been created and is owned by this instance
      33             :     /// of the object.
      34             :     LFS_Owned,
      35             :     /// The lock file already exists and is owned by some other
      36             :     /// instance.
      37             :     LFS_Shared,
      38             :     /// An error occurred while trying to create or find the lock
      39             :     /// file.
      40             :     LFS_Error
      41             :   };
      42             : 
      43             :   /// Describes the result of waiting for the owner to release the lock.
      44             :   enum WaitForUnlockResult {
      45             :     /// The lock was released successfully.
      46             :     Res_Success,
      47             :     /// Owner died while holding the lock.
      48             :     Res_OwnerDied,
      49             :     /// Reached timeout while waiting for the owner to release the lock.
      50             :     Res_Timeout
      51             :   };
      52             : 
      53             : private:
      54             :   SmallString<128> FileName;
      55             :   SmallString<128> LockFileName;
      56             :   SmallString<128> UniqueLockFileName;
      57             : 
      58             :   Optional<std::pair<std::string, int> > Owner;
      59             :   std::error_code ErrorCode;
      60             :   std::string ErrorDiagMsg;
      61             : 
      62             :   LockFileManager(const LockFileManager &) = delete;
      63             :   LockFileManager &operator=(const LockFileManager &) = delete;
      64             : 
      65             :   static Optional<std::pair<std::string, int> >
      66             :   readLockFile(StringRef LockFileName);
      67             : 
      68             :   static bool processStillExecuting(StringRef Hostname, int PID);
      69             : 
      70             : public:
      71             : 
      72             :   LockFileManager(StringRef FileName);
      73             :   ~LockFileManager();
      74             : 
      75             :   /// Determine the state of the lock file.
      76             :   LockFileState getState() const;
      77             : 
      78        1762 :   operator LockFileState() const { return getState(); }
      79             : 
      80             :   /// For a shared lock, wait until the owner releases the lock.
      81             :   WaitForUnlockResult waitForUnlock();
      82             : 
      83             :   /// Remove the lock file.  This may delete a different lock file than
      84             :   /// the one previously read if there is a race.
      85             :   std::error_code unsafeRemoveLockFile();
      86             : 
      87             :   /// Get error message, or "" if there is no error.
      88             :   std::string getErrorMessage() const;
      89             : 
      90             :   /// Set error and error message
      91           0 :   void setError(const std::error_code &EC, StringRef ErrorMsg = "") {
      92           0 :     ErrorCode = EC;
      93           0 :     ErrorDiagMsg = ErrorMsg.str();
      94           0 :   }
      95             : };
      96             : 
      97             : } // end namespace llvm
      98             : 
      99             : #endif // LLVM_SUPPORT_LOCKFILEMANAGER_H