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/STLExtras.h"
11 #include "llvm/ADT/StringExtras.h"
12 #include "llvm/Support/Errc.h"
13 #include "llvm/Support/FileSystem.h"
14 #include "llvm/Support/MemoryBuffer.h"
15 #include "llvm/Support/Path.h"
16 #include "llvm/Support/raw_ostream.h"
18 #include <sys/types.h>
27 /// \brief Attempt to read the lock file with the given name, if it exists.
29 /// \param LockFileName The name of the lock file to read.
31 /// \returns The process ID of the process that owns this lock file
32 Optional<std::pair<std::string, int> >
33 LockFileManager::readLockFile(StringRef LockFileName) {
34 // Read the owning host and PID out of the lock file. If it appears that the
35 // owning process is dead, the lock file is invalid.
36 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
37 MemoryBuffer::getFile(LockFileName);
39 sys::fs::remove(LockFileName);
42 MemoryBuffer &MB = *MBOrErr.get();
46 std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " ");
47 PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" "));
49 if (!PIDStr.getAsInteger(10, PID)) {
50 auto Owner = std::make_pair(std::string(Hostname), PID);
51 if (processStillExecuting(Owner.first, Owner.second))
55 // Delete the lock file. It's invalid anyway.
56 sys::fs::remove(LockFileName);
60 bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) {
61 #if LLVM_ON_UNIX && !defined(__ANDROID__)
65 gethostname(MyHostname, 255);
66 // Check whether the process is dead. If so, we're done.
67 if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH)
74 LockFileManager::LockFileManager(StringRef FileName)
76 this->FileName = FileName;
77 if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
81 LockFileName = this->FileName;
82 LockFileName += ".lock";
84 // If the lock file already exists, don't bother to try to create our own
85 // lock file; it won't work anyway. Just figure out who owns this lock file.
86 if ((Owner = readLockFile(LockFileName)))
89 // Create a lock file that is unique to this instance.
90 UniqueLockFileName = LockFileName;
91 UniqueLockFileName += "-%%%%%%%%";
93 if (std::error_code EC = sys::fs::createUniqueFile(
94 UniqueLockFileName.str(), UniqueLockFileID, UniqueLockFileName)) {
99 // Write our process ID to our unique lock file.
101 raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
104 // FIXME: move getpid() call into LLVM
108 gethostname(hostname, 255);
109 Out << hostname << ' ' << getpid();
111 Out << "localhost 1";
115 if (Out.has_error()) {
116 // We failed to write out PID, so make up an excuse, remove the
117 // unique lock file, and fail.
118 Error = make_error_code(errc::no_space_on_device);
119 sys::fs::remove(UniqueLockFileName.c_str());
125 // Create a link from the lock file name. If this succeeds, we're done.
127 sys::fs::create_link(UniqueLockFileName.str(), LockFileName.str());
131 if (EC != errc::file_exists) {
136 // Someone else managed to create the lock file first. Read the process ID
137 // from the lock file.
138 if ((Owner = readLockFile(LockFileName))) {
139 // Wipe out our unique lock file (it's useless now)
140 sys::fs::remove(UniqueLockFileName.str());
144 if (!sys::fs::exists(LockFileName.str())) {
145 // The previous owner released the lock file before we could read it.
146 // Try to get ownership again.
150 // There is a lock file that nobody owns; try to clean it up and get
152 if ((EC = sys::fs::remove(LockFileName.str()))) {
159 LockFileManager::LockFileState LockFileManager::getState() const {
169 LockFileManager::~LockFileManager() {
170 if (getState() != LFS_Owned)
173 // Since we own the lock, remove the lock file and our own unique lock file.
174 sys::fs::remove(LockFileName.str());
175 sys::fs::remove(UniqueLockFileName.str());
178 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
179 if (getState() != LFS_Shared)
183 unsigned long Interval = 1;
185 struct timespec Interval;
187 Interval.tv_nsec = 1000000;
189 // Don't wait more than five minutes for the file to appear.
190 unsigned MaxSeconds = 300;
191 bool LockFileGone = false;
193 // Sleep for the designated interval, to allow the owning process time to
194 // finish up and remove the lock file.
195 // FIXME: Should we hook in to system APIs to get a notification when the
196 // lock file is deleted?
200 nanosleep(&Interval, nullptr);
202 bool LockFileJustDisappeared = false;
204 // If the lock file is still expected to be there, check whether it still
208 if (!sys::fs::exists(LockFileName.str(), Exists) && !Exists) {
210 LockFileJustDisappeared = true;
214 // If the lock file is no longer there, check if the original file is
217 if (sys::fs::exists(FileName.str())) {
221 // The lock file is gone, so now we're waiting for the original file to
222 // show up. If this just happened, reset our waiting intervals and keep
224 if (LockFileJustDisappeared) {
231 Interval.tv_nsec = 1000000;
237 // If we're looking for the lock file to disappear, but the process
238 // owning the lock died without cleaning up, just bail out.
240 !processStillExecuting((*Owner).first, (*Owner).second)) {
241 return Res_OwnerDied;
244 // Exponentially increase the time we wait for the lock to be removed.
248 Interval.tv_sec *= 2;
249 Interval.tv_nsec *= 2;
250 if (Interval.tv_nsec >= 1000000000) {
252 Interval.tv_nsec -= 1000000000;
257 Interval < MaxSeconds * 1000
259 Interval.tv_sec < (time_t)MaxSeconds