1 files changed, 328 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Support/LockFileManager.cpp b/contrib/llvm-project/llvm/lib/Support/LockFileManager.cpp
new file mode 100644
index 000000000000..ea040ccf22b9
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/Support/LockFileManager.cpp
@@ -0,0 +1,328 @@
+//===--- 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/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/ExponentialBackoff.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 <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(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && (__ENVIRONMENT_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
+std::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 std::nullopt;
+  }
+  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 std::nullopt;
+}
+
+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 errnoAsErrorCode();
+
+  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));
+    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));
+    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));
+      setError(Out.error(), S);
+      sys::fs::remove(UniqueLockFileName);
+      // Don't call report_fatal_error.
+      Out.clear_error();
+      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, S);
+      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));
+      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 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,
+  // use 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
+  using namespace std::chrono_literals;
+  ExponentialBackoff Backoff(std::chrono::seconds(MaxSeconds), 10ms, 500ms);
+
+  // Wait first as this is only called when the lock is known to be held.
+  while (Backoff.waitForNextAttempt()) {
+    // FIXME: implement event-based waiting
+    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;
+  }
+
+  // Give up.
+  return Res_Timeout;
+}
+
+std::error_code LockFileManager::unsafeRemoveLockFile() {
+  return sys::fs::remove(LockFileName);
+}