1 //===--- LockFileManager.cpp - File-level Locking Utility------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
9 #include "llvm/Support/LockFileManager.h"
10 #include "llvm/ADT/StringExtras.h"
11 #include "llvm/Support/Errc.h"
12 #include "llvm/Support/FileSystem.h"
13 #include "llvm/Support/MemoryBuffer.h"
14 #include "llvm/Support/raw_ostream.h"
15 #include "llvm/Support/Signals.h"
17 #include <sys/types.h>
25 #if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050)
26 #define USE_OSX_GETHOSTUUID 1
28 #define USE_OSX_GETHOSTUUID 0
31 #if USE_OSX_GETHOSTUUID
32 #include <uuid/uuid.h>
36 /// \brief Attempt to read the lock file with the given name, if it exists.
38 /// \param LockFileName The name of the lock file to read.
40 /// \returns The process ID of the process that owns this lock file
41 Optional<std::pair<std::string, int> >
42 LockFileManager::readLockFile(StringRef LockFileName) {
43 // Read the owning host and PID out of the lock file. If it appears that the
44 // owning process is dead, the lock file is invalid.
45 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
46 MemoryBuffer::getFile(LockFileName);
48 sys::fs::remove(LockFileName);
51 MemoryBuffer &MB = *MBOrErr.get();
55 std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " ");
56 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" "));
58 if (!PIDStr.getAsInteger(10, PID)) {
59 auto Owner = std::make_pair(std::string(Hostname), PID);
60 if (processStillExecuting(Owner.first, Owner.second))
64 // Delete the lock file. It's invalid anyway.
65 sys::fs::remove(LockFileName);
69 static std::error_code getHostID(SmallVectorImpl<char> &HostID) {
72 #if USE_OSX_GETHOSTUUID
73 // On OS X, use the more stable hardware UUID instead of hostname.
74 struct timespec wait = {1, 0}; // 1 second.
76 if (gethostuuid(uuid, &wait) != 0)
77 return std::error_code(errno, std::system_category());
79 uuid_string_t UUIDStr;
80 uuid_unparse(uuid, UUIDStr);
81 assert(strlen(UUIDStr) == 36);
82 HostID.append(&UUIDStr[0], &UUIDStr[36]);
88 gethostname(hostname, 255);
95 return std::error_code();
98 bool LockFileManager::processStillExecuting(StringRef HostID, int PID) {
99 #if LLVM_ON_UNIX && !defined(__ANDROID__)
100 SmallString<256> StoredHostID;
101 if (getHostID(StoredHostID))
102 return true; // Conservatively assume it's executing on error.
104 // Check whether the process is dead. If so, we're done.
105 if (StoredHostID == HostID && getsid(PID) == -1 && errno == ESRCH)
113 /// An RAII helper object ensure that the unique lock file is removed.
115 /// Ensures that if there is an error or a signal before we finish acquiring the
116 /// lock, the unique file will be removed. And if we successfully take the lock,
117 /// the signal handler is left in place so that signals while the lock is held
118 /// will remove the unique lock file. The caller should ensure there is a
119 /// matching call to sys::DontRemoveFileOnSignal when the lock is released.
120 class RemoveUniqueLockFileOnSignal {
122 bool RemoveImmediately;
124 RemoveUniqueLockFileOnSignal(StringRef Name)
125 : Filename(Name), RemoveImmediately(true) {
126 sys::RemoveFileOnSignal(Filename, nullptr);
128 ~RemoveUniqueLockFileOnSignal() {
129 if (!RemoveImmediately) {
130 // Leave the signal handler enabled. It will be removed when the lock is
134 sys::fs::remove(Filename);
135 sys::DontRemoveFileOnSignal(Filename);
137 void lockAcquired() { RemoveImmediately = false; }
139 } // end anonymous namespace
141 LockFileManager::LockFileManager(StringRef FileName)
143 this->FileName = FileName;
144 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
148 LockFileName = this->FileName;
149 LockFileName += ".lock";
151 // If the lock file already exists, don't bother to try to create our own
152 // lock file; it won't work anyway. Just figure out who owns this lock file.
153 if ((Owner = readLockFile(LockFileName)))
156 // Create a lock file that is unique to this instance.
157 UniqueLockFileName = LockFileName;
158 UniqueLockFileName += "-%%%%%%%%";
159 int UniqueLockFileID;
160 if (std::error_code EC = sys::fs::createUniqueFile(
161 UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) {
166 // Write our process ID to our unique lock file.
168 SmallString<256> HostID;
169 if (auto EC = getHostID(HostID)) {
174 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
175 Out << HostID << ' ';
183 if (Out.has_error()) {
184 // We failed to write out PID, so make up an excuse, remove the
185 // unique lock file, and fail.
186 Error = make_error_code(errc::no_space_on_device);
187 sys::fs::remove(UniqueLockFileName);
192 // Clean up the unique file on signal, which also releases the lock if it is
193 // held since the .lock symlink will point to a nonexistent file.
194 RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);
197 // Create a link from the lock file name. If this succeeds, we're done.
199 sys::fs::create_link(UniqueLockFileName, LockFileName);
201 RemoveUniqueFile.lockAcquired();
205 if (EC != errc::file_exists) {
210 // Someone else managed to create the lock file first. Read the process ID
211 // from the lock file.
212 if ((Owner = readLockFile(LockFileName))) {
213 // Wipe out our unique lock file (it's useless now)
214 sys::fs::remove(UniqueLockFileName);
218 if (!sys::fs::exists(LockFileName)) {
219 // The previous owner released the lock file before we could read it.
220 // Try to get ownership again.
224 // There is a lock file that nobody owns; try to clean it up and get
226 if ((EC = sys::fs::remove(LockFileName))) {
233 LockFileManager::LockFileState LockFileManager::getState() const {
243 LockFileManager::~LockFileManager() {
244 if (getState() != LFS_Owned)
247 // Since we own the lock, remove the lock file and our own unique lock file.
248 sys::fs::remove(LockFileName);
249 sys::fs::remove(UniqueLockFileName);
250 // The unique file is now gone, so remove it from the signal handler. This
251 // matches a sys::RemoveFileOnSignal() in LockFileManager().
252 sys::DontRemoveFileOnSignal(UniqueLockFileName);
255 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
256 if (getState() != LFS_Shared)
260 unsigned long Interval = 1;
262 struct timespec Interval;
264 Interval.tv_nsec = 1000000;
266 // Don't wait more than five minutes per iteration. Total timeout for the file
267 // to appear is ~8.5 mins.
268 const unsigned MaxSeconds = 5*60;
270 // Sleep for the designated interval, to allow the owning process time to
271 // finish up and remove the lock file.
272 // FIXME: Should we hook in to system APIs to get a notification when the
273 // lock file is deleted?
277 nanosleep(&Interval, nullptr);
280 if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
281 errc::no_such_file_or_directory) {
282 // If the original file wasn't created, somone thought the lock was dead.
283 if (!sys::fs::exists(FileName))
284 return Res_OwnerDied;
288 // If the process owning the lock died without cleaning up, just bail out.
289 if (!processStillExecuting((*Owner).first, (*Owner).second))
290 return Res_OwnerDied;
292 // Exponentially increase the time we wait for the lock to be removed.
296 Interval.tv_sec *= 2;
297 Interval.tv_nsec *= 2;
298 if (Interval.tv_nsec >= 1000000000) {
300 Interval.tv_nsec -= 1000000000;
305 Interval < MaxSeconds * 1000
307 Interval.tv_sec < (time_t)MaxSeconds
315 std::error_code LockFileManager::unsafeRemoveLockFile() {
316 return sys::fs::remove(LockFileName);