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+//===--- 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 "llvm/Support/Signals.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
+
+#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;
+
+/// \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;
+}
+
+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)) {
+ 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.
+ {
+ SmallString<256> HostID;
+ if (auto EC = getHostID(HostID)) {
+ Error = EC;
+ return;
+ }
+
+ raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
+ Out << HostID << ' ';
+#if LLVM_ON_UNIX
+ Out << getpid();
+#else
+ Out << "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;
+ }
+ }
+
+ // 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 (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) {
+ RemoveUniqueFile.lockAcquired();
+ 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);
+ // 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() {
+ 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);
+}
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