1 files changed, 238 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Support/LockFileManager.cpp b/contrib/llvm/lib/Support/LockFileManager.cpp
new file mode 100644
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+++ b/contrib/llvm/lib/Support/LockFileManager.cpp
@@ -0,0 +1,238 @@
+//===--- LockFileManager.cpp - File-level Locking Utility------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/Support/LockFileManager.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+#include <sys/stat.h>
+#include <sys/types.h>
+#if LLVM_ON_WIN32
+#include <windows.h>
+#endif
+#if LLVM_ON_UNIX
+#include <unistd.h>
+#endif
+using namespace llvm;
+
+/// \brief 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;
+}
+
+bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) {
+#if LLVM_ON_UNIX && !defined(__ANDROID__)
+  char MyHostname[256];
+  MyHostname[255] = 0;
+  MyHostname[0] = 0;
+  gethostname(MyHostname, 255);
+  // Check whether the process is dead. If so, we're done.
+  if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH)
+    return false;
+#endif
+
+  return true;
+}
+
+LockFileManager::LockFileManager(StringRef FileName)
+{
+  this->FileName = FileName;
+  if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
+    Error = EC;
+    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)) {
+    Error = EC;
+    return;
+  }
+
+  // Write our process ID to our unique lock file.
+  {
+    raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
+
+#if LLVM_ON_UNIX
+    // FIXME: move getpid() call into LLVM
+    char hostname[256];
+    hostname[255] = 0;
+    hostname[0] = 0;
+    gethostname(hostname, 255);
+    Out << hostname << ' ' << getpid();
+#else
+    Out << "localhost 1";
+#endif
+    Out.close();
+
+    if (Out.has_error()) {
+      // We failed to write out PID, so make up an excuse, remove the
+      // unique lock file, and fail.
+      Error = make_error_code(errc::no_space_on_device);
+      sys::fs::remove(UniqueLockFileName);
+      return;
+    }
+  }
+
+  while (1) {
+    // 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)
+      return;
+
+    if (EC != errc::file_exists) {
+      Error = EC;
+      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))) {
+      Error = EC;
+      return;
+    }
+  }
+}
+
+LockFileManager::LockFileState LockFileManager::getState() const {
+  if (Owner)
+    return LFS_Shared;
+
+  if (Error)
+    return LFS_Error;
+
+  return LFS_Owned;
+}
+
+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);
+}
+
+LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
+  if (getState() != LFS_Shared)
+    return Res_Success;
+
+#if LLVM_ON_WIN32
+  unsigned long Interval = 1;
+#else
+  struct timespec Interval;
+  Interval.tv_sec = 0;
+  Interval.tv_nsec = 1000000;
+#endif
+  // Don't wait more than five minutes per iteration. Total timeout for the file
+  // to appear is ~8.5 mins.
+  const unsigned MaxSeconds = 5*60;
+  do {
+    // Sleep for the designated interval, to allow the owning process time to
+    // finish up and remove the lock file.
+    // FIXME: Should we hook in to system APIs to get a notification when the
+    // lock file is deleted?
+#if LLVM_ON_WIN32
+    Sleep(Interval);
+#else
+    nanosleep(&Interval, nullptr);
+#endif
+
+    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;
+
+    // Exponentially increase the time we wait for the lock to be removed.
+#if LLVM_ON_WIN32
+    Interval *= 2;
+#else
+    Interval.tv_sec *= 2;
+    Interval.tv_nsec *= 2;
+    if (Interval.tv_nsec >= 1000000000) {
+      ++Interval.tv_sec;
+      Interval.tv_nsec -= 1000000000;
+    }
+#endif
+  } while (
+#if LLVM_ON_WIN32
+           Interval < MaxSeconds * 1000
+#else
+           Interval.tv_sec < (time_t)MaxSeconds
+#endif
+           );
+
+  // Give up.
+  return Res_Timeout;
+}
+
+std::error_code LockFileManager::unsafeRemoveLockFile() {
+  return sys::fs::remove(LockFileName);
+}