| //===--- 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(__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 |
| 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); |
| } |