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>
26 /// \brief Attempt to read the lock file with the given name, if it exists.
28 /// \param LockFileName The name of the lock file to read.
30 /// \returns The process ID of the process that owns this lock file
31 Optional<std::pair<std::string, int> >
32 LockFileManager::readLockFile(StringRef LockFileName) {
33 // Read the owning host and PID out of the lock file. If it appears that the
34 // owning process is dead, the lock file is invalid.
35 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
36 MemoryBuffer::getFile(LockFileName);
38 sys::fs::remove(LockFileName);
41 MemoryBuffer &MB = *MBOrErr.get();
45 std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " ");
46 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" "));
48 if (!PIDStr.getAsInteger(10, PID)) {
49 auto Owner = std::make_pair(std::string(Hostname), PID);
50 if (processStillExecuting(Owner.first, Owner.second))
54 // Delete the lock file. It's invalid anyway.
55 sys::fs::remove(LockFileName);
59 bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) {
60 #if LLVM_ON_UNIX && !defined(__ANDROID__)
64 gethostname(MyHostname, 255);
65 // Check whether the process is dead. If so, we're done.
66 if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH)
74 /// An RAII helper object ensure that the unique lock file is removed.
76 /// Ensures that if there is an error or a signal before we finish acquiring the
77 /// lock, the unique file will be removed. And if we successfully take the lock,
78 /// the signal handler is left in place so that signals while the lock is held
79 /// will remove the unique lock file. The caller should ensure there is a
80 /// matching call to sys::DontRemoveFileOnSignal when the lock is released.
81 class RemoveUniqueLockFileOnSignal {
83 bool RemoveImmediately;
85 RemoveUniqueLockFileOnSignal(StringRef Name)
86 : Filename(Name), RemoveImmediately(true) {
87 sys::RemoveFileOnSignal(Filename, nullptr);
89 ~RemoveUniqueLockFileOnSignal() {
90 if (!RemoveImmediately) {
91 // Leave the signal handler enabled. It will be removed when the lock is
95 sys::fs::remove(Filename);
96 sys::DontRemoveFileOnSignal(Filename);
98 void lockAcquired() { RemoveImmediately = false; }
100 } // end anonymous namespace
102 LockFileManager::LockFileManager(StringRef FileName)
104 this->FileName = FileName;
105 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
109 LockFileName = this->FileName;
110 LockFileName += ".lock";
112 // If the lock file already exists, don't bother to try to create our own
113 // lock file; it won't work anyway. Just figure out who owns this lock file.
114 if ((Owner = readLockFile(LockFileName)))
117 // Create a lock file that is unique to this instance.
118 UniqueLockFileName = LockFileName;
119 UniqueLockFileName += "-%%%%%%%%";
120 int UniqueLockFileID;
121 if (std::error_code EC = sys::fs::createUniqueFile(
122 UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) {
127 // Write our process ID to our unique lock file.
129 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
132 // FIXME: move getpid() call into LLVM
136 gethostname(hostname, 255);
137 Out << hostname << ' ' << getpid();
139 Out << "localhost 1";
143 if (Out.has_error()) {
144 // We failed to write out PID, so make up an excuse, remove the
145 // unique lock file, and fail.
146 Error = make_error_code(errc::no_space_on_device);
147 sys::fs::remove(UniqueLockFileName);
152 // Clean up the unique file on signal, which also releases the lock if it is
153 // held since the .lock symlink will point to a nonexistent file.
154 RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);
157 // Create a link from the lock file name. If this succeeds, we're done.
159 sys::fs::create_link(UniqueLockFileName, LockFileName);
161 RemoveUniqueFile.lockAcquired();
165 if (EC != errc::file_exists) {
170 // Someone else managed to create the lock file first. Read the process ID
171 // from the lock file.
172 if ((Owner = readLockFile(LockFileName))) {
173 // Wipe out our unique lock file (it's useless now)
174 sys::fs::remove(UniqueLockFileName);
178 if (!sys::fs::exists(LockFileName)) {
179 // The previous owner released the lock file before we could read it.
180 // Try to get ownership again.
184 // There is a lock file that nobody owns; try to clean it up and get
186 if ((EC = sys::fs::remove(LockFileName))) {
193 LockFileManager::LockFileState LockFileManager::getState() const {
203 LockFileManager::~LockFileManager() {
204 if (getState() != LFS_Owned)
207 // Since we own the lock, remove the lock file and our own unique lock file.
208 sys::fs::remove(LockFileName);
209 sys::fs::remove(UniqueLockFileName);
210 // The unique file is now gone, so remove it from the signal handler. This
211 // matches a sys::RemoveFileOnSignal() in LockFileManager().
212 sys::DontRemoveFileOnSignal(UniqueLockFileName);
215 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
216 if (getState() != LFS_Shared)
220 unsigned long Interval = 1;
222 struct timespec Interval;
224 Interval.tv_nsec = 1000000;
226 // Don't wait more than five minutes per iteration. Total timeout for the file
227 // to appear is ~8.5 mins.
228 const unsigned MaxSeconds = 5*60;
230 // Sleep for the designated interval, to allow the owning process time to
231 // finish up and remove the lock file.
232 // FIXME: Should we hook in to system APIs to get a notification when the
233 // lock file is deleted?
237 nanosleep(&Interval, nullptr);
240 if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
241 errc::no_such_file_or_directory) {
242 // If the original file wasn't created, somone thought the lock was dead.
243 if (!sys::fs::exists(FileName))
244 return Res_OwnerDied;
248 // If the process owning the lock died without cleaning up, just bail out.
249 if (!processStillExecuting((*Owner).first, (*Owner).second))
250 return Res_OwnerDied;
252 // Exponentially increase the time we wait for the lock to be removed.
256 Interval.tv_sec *= 2;
257 Interval.tv_nsec *= 2;
258 if (Interval.tv_nsec >= 1000000000) {
260 Interval.tv_nsec -= 1000000000;
265 Interval < MaxSeconds * 1000
267 Interval.tv_sec < (time_t)MaxSeconds
275 std::error_code LockFileManager::unsafeRemoveLockFile() {
276 return sys::fs::remove(LockFileName);