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📄 AArch64TargetParser.cpp(8 KB)
📄 ABIBreak.cpp(811 B)
📄 AMDGPUMetadata.cpp(9.37 KB)
📄 APFloat.cpp(155.26 KB)
📄 APInt.cpp(98.08 KB)
📄 APSInt.cpp(1.44 KB)
📄 ARMAttributeParser.cpp(13.94 KB)
📄 ARMBuildAttrs.cpp(3.45 KB)
📄 ARMTargetParser.cpp(18.09 KB)
📄 ARMWinEH.cpp(1.08 KB)
📄 Allocator.cpp(1.35 KB)
📄 Atomic.cpp(1.6 KB)
📄 BinaryStreamError.cpp(1.76 KB)
📄 BinaryStreamReader.cpp(5.24 KB)
📄 BinaryStreamRef.cpp(4.76 KB)
📄 BinaryStreamWriter.cpp(3.36 KB)
📄 BlockFrequency.cpp(2.12 KB)
📄 BranchProbability.cpp(3.44 KB)
📄 BuryPointer.cpp(1.11 KB)
📄 COM.cpp(737 B)
📄 COPYRIGHT.regex(2.65 KB)
📄 CRC.cpp(5.23 KB)
📄 CachePruning.cpp(10.33 KB)
📄 Chrono.cpp(3.17 KB)
📄 CodeGenCoverage.cpp(3.61 KB)
📄 CommandLine.cpp(89.06 KB)
📄 Compression.cpp(3.84 KB)
📄 ConvertUTF.cpp(27.27 KB)
📄 ConvertUTFWrapper.cpp(8.66 KB)
📄 CrashRecoveryContext.cpp(15.45 KB)
📄 DAGDeltaAlgorithm.cpp(12.47 KB)
📄 DJB.cpp(2.71 KB)
📄 DataExtractor.cpp(7.25 KB)
📄 Debug.cpp(5.64 KB)
📄 DebugCounter.cpp(4.95 KB)
📄 DeltaAlgorithm.cpp(3.41 KB)
📄 DynamicLibrary.cpp(6.25 KB)
📄 ELFAttributeParser.cpp(7.27 KB)
📄 ELFAttributes.cpp(1.27 KB)
📄 Errno.cpp(2.18 KB)
📄 Error.cpp(4.72 KB)
📄 ErrorHandling.cpp(11.08 KB)
📄 ExtensibleRTTI.cpp(446 B)
📄 FileCheck.cpp(95.77 KB)
📄 FileCheckImpl.h(34.14 KB)
📄 FileCollector.cpp(9.01 KB)
📄 FileOutputBuffer.cpp(6.62 KB)
📄 FileUtilities.cpp(10.81 KB)
📄 FoldingSet.cpp(15.89 KB)
📄 FormatVariadic.cpp(5.17 KB)
📄 FormattedStream.cpp(5.29 KB)
📄 GlobPattern.cpp(5 KB)
📄 GraphWriter.cpp(9.21 KB)
📄 Hashing.cpp(1.16 KB)
📄 Host.cpp(51.63 KB)
📄 InitLLVM.cpp(1.92 KB)
📄 IntEqClasses.cpp(2.18 KB)
📄 IntervalMap.cpp(4.4 KB)
📄 ItaniumManglingCanonicalizer.cpp(10.77 KB)
📄 JSON.cpp(19.1 KB)
📄 KnownBits.cpp(3.78 KB)
📄 LEB128.cpp(1.19 KB)
📄 LineIterator.cpp(2.61 KB)
📄 Locale.cpp(377 B)
📄 LockFileManager.cpp(10.64 KB)
📄 LowLevelType.cpp(2.09 KB)
📄 MD5.cpp(8.99 KB)
📄 ManagedStatic.cpp(2.37 KB)
📄 MathExtras.cpp(913 B)
📄 MemAlloc.cpp(1.01 KB)
📄 Memory.cpp(1.57 KB)
📄 MemoryBuffer.cpp(18.99 KB)
📄 NativeFormatting.cpp(7.54 KB)
📄 OptimizedStructLayout.cpp(16.7 KB)
📄 Optional.cpp(530 B)
📄 Parallel.cpp(5.08 KB)
📄 Path.cpp(36.52 KB)
📄 PluginLoader.cpp(1.63 KB)
📄 PrettyStackTrace.cpp(10.33 KB)
📄 Process.cpp(3.27 KB)
📄 Program.cpp(3.54 KB)
📄 RISCVAttributeParser.cpp(2.06 KB)
📄 RISCVAttributes.cpp(970 B)
📄 RWMutex.cpp(3.23 KB)
📄 RandomNumberGenerator.cpp(2.86 KB)
📄 Regex.cpp(6.38 KB)
📄 SHA1.cpp(10.43 KB)
📄 ScaledNumber.cpp(9.09 KB)
📄 ScopedPrinter.cpp(1.19 KB)
📄 Signals.cpp(8.35 KB)
📄 Signposts.cpp(3.24 KB)
📄 SmallPtrSet.cpp(9.21 KB)
📄 SmallVector.cpp(3.99 KB)
📄 SourceMgr.cpp(20.08 KB)
📄 SpecialCaseList.cpp(7.48 KB)
📄 Statistic.cpp(8.85 KB)
📄 StringExtras.cpp(4.34 KB)
📄 StringMap.cpp(9.31 KB)
📄 StringRef.cpp(17.41 KB)
📄 StringSaver.cpp(882 B)
📄 SuffixTree.cpp(7.23 KB)
📄 SymbolRemappingReader.cpp(2.94 KB)
📄 SystemUtils.cpp(1.06 KB)
📄 TarWriter.cpp(7.23 KB)
📄 TargetParser.cpp(9.86 KB)
📄 TargetRegistry.cpp(4.6 KB)
📄 ThreadLocal.cpp(1.68 KB)
📄 ThreadPool.cpp(4.4 KB)
📄 Threading.cpp(4.55 KB)
📄 TimeProfiler.cpp(11.63 KB)
📄 Timer.cpp(14.14 KB)
📄 ToolOutputFile.cpp(1.83 KB)
📄 TrigramIndex.cpp(3.24 KB)
📄 Triple.cpp(53.17 KB)
📄 Twine.cpp(4.6 KB)
📄 Unicode.cpp(20.14 KB)
📄 UnicodeCaseFold.cpp(15.32 KB)
📁 Unix
📄 Valgrind.cpp(1.6 KB)
📄 VersionTuple.cpp(2.74 KB)
📄 VirtualFileSystem.cpp(74.17 KB)
📄 Watchdog.cpp(738 B)
📁 Windows
📄 WithColor.cpp(4.35 KB)
📄 X86TargetParser.cpp(27.21 KB)
📄 YAMLParser.cpp(68.53 KB)
📄 YAMLTraits.cpp(28.37 KB)
📄 Z3Solver.cpp(31.44 KB)
📄 circular_raw_ostream.cpp(1.3 KB)
📄 raw_os_ostream.cpp(995 B)
📄 raw_ostream.cpp(28.97 KB)
📄 regcomp.c(39.42 KB)
📄 regengine.inc(26.49 KB)
📄 regerror.c(4.42 KB)
📄 regex2.h(6.82 KB)
📄 regex_impl.h(3.63 KB)
📄 regexec.c(5.71 KB)
📄 regfree.c(2.49 KB)
📄 regstrlcpy.c(1.56 KB)
📄 regutils.h(2.25 KB)
📄 xxhash.cpp(4.07 KB)

Editing: LockFileManager.cpp

//===--- LockFileManager.cpp - File-level Locking Utility------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/LockFileManager.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/raw_ostream.h"
#include <cerrno>
#include <chrono>
#include <ctime>
#include <memory>
#include <random>
#include <sys/stat.h>
#include <sys/types.h>
#include <system_error>
#include <thread>
#include <tuple>

#ifdef _WIN32
#include <windows.h>
#endif
#if LLVM_ON_UNIX
#include <unistd.h>
#endif

#if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050)
#define USE_OSX_GETHOSTUUID 1
#else
#define USE_OSX_GETHOSTUUID 0
#endif

#if USE_OSX_GETHOSTUUID
#include <uuid/uuid.h>
#endif

using namespace llvm;

/// Attempt to read the lock file with the given name, if it exists.
///
/// \param LockFileName The name of the lock file to read.
///
/// \returns The process ID of the process that owns this lock file
Optional<std::pair<std::string, int> >
LockFileManager::readLockFile(StringRef LockFileName) {
  // Read the owning host and PID out of the lock file. If it appears that the
  // owning process is dead, the lock file is invalid.
  ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
      MemoryBuffer::getFile(LockFileName);
  if (!MBOrErr) {
    sys::fs::remove(LockFileName);
    return None;
  }
  MemoryBuffer &MB = *MBOrErr.get();

StringRef Hostname;
  StringRef PIDStr;
  std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " ");
  PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" "));
  int PID;
  if (!PIDStr.getAsInteger(10, PID)) {
    auto Owner = std::make_pair(std::string(Hostname), PID);
    if (processStillExecuting(Owner.first, Owner.second))
      return Owner;
  }

// Delete the lock file. It's invalid anyway.
  sys::fs::remove(LockFileName);
  return None;
}

static std::error_code getHostID(SmallVectorImpl<char> &HostID) {
  HostID.clear();

#if USE_OSX_GETHOSTUUID
  // On OS X, use the more stable hardware UUID instead of hostname.
  struct timespec wait = {1, 0}; // 1 second.
  uuid_t uuid;
  if (gethostuuid(uuid, &wait) != 0)
    return std::error_code(errno, std::system_category());

uuid_string_t UUIDStr;
  uuid_unparse(uuid, UUIDStr);
  StringRef UUIDRef(UUIDStr);
  HostID.append(UUIDRef.begin(), UUIDRef.end());

#elif LLVM_ON_UNIX
  char HostName[256];
  HostName[255] = 0;
  HostName[0] = 0;
  gethostname(HostName, 255);
  StringRef HostNameRef(HostName);
  HostID.append(HostNameRef.begin(), HostNameRef.end());

#else
  StringRef Dummy("localhost");
  HostID.append(Dummy.begin(), Dummy.end());
#endif

return std::error_code();
}

bool LockFileManager::processStillExecuting(StringRef HostID, int PID) {
#if LLVM_ON_UNIX && !defined(__ANDROID__)
  SmallString<256> StoredHostID;
  if (getHostID(StoredHostID))
    return true; // Conservatively assume it's executing on error.

// Check whether the process is dead. If so, we're done.
  if (StoredHostID == HostID && getsid(PID) == -1 && errno == ESRCH)
    return false;
#endif

return true;
}

namespace {

/// An RAII helper object ensure that the unique lock file is removed.
///
/// Ensures that if there is an error or a signal before we finish acquiring the
/// lock, the unique file will be removed. And if we successfully take the lock,
/// the signal handler is left in place so that signals while the lock is held
/// will remove the unique lock file. The caller should ensure there is a
/// matching call to sys::DontRemoveFileOnSignal when the lock is released.
class RemoveUniqueLockFileOnSignal {
  StringRef Filename;
  bool RemoveImmediately;
public:
  RemoveUniqueLockFileOnSignal(StringRef Name)
  : Filename(Name), RemoveImmediately(true) {
    sys::RemoveFileOnSignal(Filename, nullptr);
  }

~RemoveUniqueLockFileOnSignal() {
    if (!RemoveImmediately) {
      // Leave the signal handler enabled. It will be removed when the lock is
      // released.
      return;
    }
    sys::fs::remove(Filename);
    sys::DontRemoveFileOnSignal(Filename);
  }

void lockAcquired() { RemoveImmediately = false; }
};

} // end anonymous namespace

LockFileManager::LockFileManager(StringRef FileName)
{
  this->FileName = FileName;
  if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
    std::string S("failed to obtain absolute path for ");
    S.append(std::string(this->FileName.str()));
    setError(EC, S);
    return;
  }
  LockFileName = this->FileName;
  LockFileName += ".lock";

// If the lock file already exists, don't bother to try to create our own
  // lock file; it won't work anyway. Just figure out who owns this lock file.
  if ((Owner = readLockFile(LockFileName)))
    return;

// Create a lock file that is unique to this instance.
  UniqueLockFileName = LockFileName;
  UniqueLockFileName += "-%%%%%%%%";
  int UniqueLockFileID;
  if (std::error_code EC = sys::fs::createUniqueFile(
          UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) {
    std::string S("failed to create unique file ");
    S.append(std::string(UniqueLockFileName.str()));
    setError(EC, S);
    return;
  }

// Write our process ID to our unique lock file.
  {
    SmallString<256> HostID;
    if (auto EC = getHostID(HostID)) {
      setError(EC, "failed to get host id");
      return;
    }

raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
    Out << HostID << ' ' << sys::Process::getProcessId();
    Out.close();

if (Out.has_error()) {
      // We failed to write out PID, so report the error, remove the
      // unique lock file, and fail.
      std::string S("failed to write to ");
      S.append(std::string(UniqueLockFileName.str()));
      setError(Out.error(), S);
      sys::fs::remove(UniqueLockFileName);
      return;
    }
  }

// Clean up the unique file on signal, which also releases the lock if it is
  // held since the .lock symlink will point to a nonexistent file.
  RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);

while (true) {
    // Create a link from the lock file name. If this succeeds, we're done.
    std::error_code EC =
        sys::fs::create_link(UniqueLockFileName, LockFileName);
    if (!EC) {
      RemoveUniqueFile.lockAcquired();
      return;
    }

if (EC != errc::file_exists) {
      std::string S("failed to create link ");
      raw_string_ostream OSS(S);
      OSS << LockFileName.str() << " to " << UniqueLockFileName.str();
      setError(EC, OSS.str());
      return;
    }

// Someone else managed to create the lock file first. Read the process ID
    // from the lock file.
    if ((Owner = readLockFile(LockFileName))) {
      // Wipe out our unique lock file (it's useless now)
      sys::fs::remove(UniqueLockFileName);
      return;
    }

if (!sys::fs::exists(LockFileName)) {
      // The previous owner released the lock file before we could read it.
      // Try to get ownership again.
      continue;
    }

// There is a lock file that nobody owns; try to clean it up and get
    // ownership.
    if ((EC = sys::fs::remove(LockFileName))) {
      std::string S("failed to remove lockfile ");
      S.append(std::string(UniqueLockFileName.str()));
      setError(EC, S);
      return;
    }
  }
}

LockFileManager::LockFileState LockFileManager::getState() const {
  if (Owner)
    return LFS_Shared;

if (ErrorCode)
    return LFS_Error;

return LFS_Owned;
}

std::string LockFileManager::getErrorMessage() const {
  if (ErrorCode) {
    std::string Str(ErrorDiagMsg);
    std::string ErrCodeMsg = ErrorCode.message();
    raw_string_ostream OSS(Str);
    if (!ErrCodeMsg.empty())
      OSS << ": " << ErrCodeMsg;
    return OSS.str();
  }
  return "";
}

LockFileManager::~LockFileManager() {
  if (getState() != LFS_Owned)
    return;

// Since we own the lock, remove the lock file and our own unique lock file.
  sys::fs::remove(LockFileName);
  sys::fs::remove(UniqueLockFileName);
  // The unique file is now gone, so remove it from the signal handler. This
  // matches a sys::RemoveFileOnSignal() in LockFileManager().
  sys::DontRemoveFileOnSignal(UniqueLockFileName);
}

LockFileManager::WaitForUnlockResult
LockFileManager::waitForUnlock(const unsigned MaxSeconds) {
  if (getState() != LFS_Shared)
    return Res_Success;

// Since we don't yet have an event-based method to wait for the lock file,
  // implement randomized exponential backoff, similar to Ethernet collision
  // algorithm. This improves performance on machines with high core counts
  // when the file lock is heavily contended by multiple clang processes
  const unsigned long MinWaitDurationMS = 10;
  const unsigned long MaxWaitMultiplier = 50; // 500ms max wait
  unsigned long WaitMultiplier = 1;
  unsigned long ElapsedTimeSeconds = 0;

std::random_device Device;
  std::default_random_engine Engine(Device());

auto StartTime = std::chrono::steady_clock::now();

do {
    // FIXME: implement event-based waiting

// Sleep for the designated interval, to allow the owning process time to
    // finish up and remove the lock file.
    std::uniform_int_distribution<unsigned long> Distribution(1,
                                                              WaitMultiplier);
    unsigned long WaitDurationMS = MinWaitDurationMS * Distribution(Engine);
    std::this_thread::sleep_for(std::chrono::milliseconds(WaitDurationMS));

if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
        errc::no_such_file_or_directory) {
      // If the original file wasn't created, somone thought the lock was dead.
      if (!sys::fs::exists(FileName))
        return Res_OwnerDied;
      return Res_Success;
    }

// If the process owning the lock died without cleaning up, just bail out.
    if (!processStillExecuting((*Owner).first, (*Owner).second))
      return Res_OwnerDied;

WaitMultiplier *= 2;
    if (WaitMultiplier > MaxWaitMultiplier) {
      WaitMultiplier = MaxWaitMultiplier;
    }

ElapsedTimeSeconds = std::chrono::duration_cast<std::chrono::seconds>(
                             std::chrono::steady_clock::now() - StartTime)
                             .count();

} while (ElapsedTimeSeconds < MaxSeconds);

// Give up.
  return Res_Timeout;
}

std::error_code LockFileManager::unsafeRemoveLockFile() {
  return sys::fs::remove(LockFileName);
}

003 File Manager

Editing: LockFileManager.cpp

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