Line data Source code
1 : //===--- LockFileManager.cpp - File-level Locking Utility------------------===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 :
10 : #include "llvm/Support/LockFileManager.h"
11 : #include "llvm/ADT/None.h"
12 : #include "llvm/ADT/SmallVector.h"
13 : #include "llvm/ADT/StringExtras.h"
14 : #include "llvm/Support/Errc.h"
15 : #include "llvm/Support/ErrorOr.h"
16 : #include "llvm/Support/FileSystem.h"
17 : #include "llvm/Support/MemoryBuffer.h"
18 : #include "llvm/Support/Signals.h"
19 : #include "llvm/Support/raw_ostream.h"
20 : #include <cerrno>
21 : #include <ctime>
22 : #include <memory>
23 : #include <sys/stat.h>
24 : #include <sys/types.h>
25 : #include <system_error>
26 : #include <tuple>
27 : #ifdef _WIN32
28 : #include <windows.h>
29 : #endif
30 : #if LLVM_ON_UNIX
31 : #include <unistd.h>
32 : #endif
33 :
34 : #if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050)
35 : #define USE_OSX_GETHOSTUUID 1
36 : #else
37 : #define USE_OSX_GETHOSTUUID 0
38 : #endif
39 :
40 : #if USE_OSX_GETHOSTUUID
41 : #include <uuid/uuid.h>
42 : #endif
43 :
44 : using namespace llvm;
45 :
46 : /// Attempt to read the lock file with the given name, if it exists.
47 : ///
48 : /// \param LockFileName The name of the lock file to read.
49 : ///
50 : /// \returns The process ID of the process that owns this lock file
51 : Optional<std::pair<std::string, int> >
52 1765 : LockFileManager::readLockFile(StringRef LockFileName) {
53 : // Read the owning host and PID out of the lock file. If it appears that the
54 : // owning process is dead, the lock file is invalid.
55 : ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
56 1765 : MemoryBuffer::getFile(LockFileName);
57 1765 : if (!MBOrErr) {
58 1760 : sys::fs::remove(LockFileName);
59 : return None;
60 : }
61 : MemoryBuffer &MB = *MBOrErr.get();
62 :
63 : StringRef Hostname;
64 5 : StringRef PIDStr;
65 5 : std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " ");
66 10 : PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" "));
67 : int PID;
68 5 : if (!PIDStr.getAsInteger(10, PID)) {
69 5 : auto Owner = std::make_pair(std::string(Hostname), PID);
70 5 : if (processStillExecuting(Owner.first, Owner.second))
71 : return Owner;
72 : }
73 :
74 : // Delete the lock file. It's invalid anyway.
75 0 : sys::fs::remove(LockFileName);
76 : return None;
77 : }
78 :
79 1805 : static std::error_code getHostID(SmallVectorImpl<char> &HostID) {
80 : HostID.clear();
81 :
82 : #if USE_OSX_GETHOSTUUID
83 : // On OS X, use the more stable hardware UUID instead of hostname.
84 : struct timespec wait = {1, 0}; // 1 second.
85 : uuid_t uuid;
86 : if (gethostuuid(uuid, &wait) != 0)
87 : return std::error_code(errno, std::system_category());
88 :
89 : uuid_string_t UUIDStr;
90 : uuid_unparse(uuid, UUIDStr);
91 : StringRef UUIDRef(UUIDStr);
92 : HostID.append(UUIDRef.begin(), UUIDRef.end());
93 :
94 : #elif LLVM_ON_UNIX
95 : char HostName[256];
96 1805 : HostName[255] = 0;
97 1805 : HostName[0] = 0;
98 1805 : gethostname(HostName, 255);
99 : StringRef HostNameRef(HostName);
100 1805 : HostID.append(HostNameRef.begin(), HostNameRef.end());
101 :
102 : #else
103 : StringRef Dummy("localhost");
104 : HostID.append(Dummy.begin(), Dummy.end());
105 : #endif
106 :
107 1805 : return std::error_code();
108 : }
109 :
110 53 : bool LockFileManager::processStillExecuting(StringRef HostID, int PID) {
111 : #if LLVM_ON_UNIX && !defined(__ANDROID__)
112 : SmallString<256> StoredHostID;
113 53 : if (getHostID(StoredHostID))
114 : return true; // Conservatively assume it's executing on error.
115 :
116 : // Check whether the process is dead. If so, we're done.
117 53 : if (StoredHostID == HostID && getsid(PID) == -1 && errno == ESRCH)
118 0 : return false;
119 : #endif
120 :
121 : return true;
122 : }
123 :
124 : namespace {
125 :
126 : /// An RAII helper object ensure that the unique lock file is removed.
127 : ///
128 : /// Ensures that if there is an error or a signal before we finish acquiring the
129 : /// lock, the unique file will be removed. And if we successfully take the lock,
130 : /// the signal handler is left in place so that signals while the lock is held
131 : /// will remove the unique lock file. The caller should ensure there is a
132 : /// matching call to sys::DontRemoveFileOnSignal when the lock is released.
133 : class RemoveUniqueLockFileOnSignal {
134 : StringRef Filename;
135 : bool RemoveImmediately;
136 : public:
137 : RemoveUniqueLockFileOnSignal(StringRef Name)
138 1752 : : Filename(Name), RemoveImmediately(true) {
139 1752 : sys::RemoveFileOnSignal(Filename, nullptr);
140 : }
141 :
142 0 : ~RemoveUniqueLockFileOnSignal() {
143 1752 : if (!RemoveImmediately) {
144 : // Leave the signal handler enabled. It will be removed when the lock is
145 : // released.
146 1752 : return;
147 : }
148 0 : sys::fs::remove(Filename);
149 0 : sys::DontRemoveFileOnSignal(Filename);
150 1752 : }
151 :
152 1752 : void lockAcquired() { RemoveImmediately = false; }
153 : };
154 :
155 : } // end anonymous namespace
156 :
157 1765 : LockFileManager::LockFileManager(StringRef FileName)
158 : {
159 : this->FileName = FileName;
160 1765 : if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
161 0 : std::string S("failed to obtain absolute path for ");
162 0 : S.append(this->FileName.str());
163 0 : setError(EC, S);
164 : return;
165 : }
166 : LockFileName = this->FileName;
167 : LockFileName += ".lock";
168 :
169 : // If the lock file already exists, don't bother to try to create our own
170 : // lock file; it won't work anyway. Just figure out who owns this lock file.
171 3535 : if ((Owner = readLockFile(LockFileName)))
172 : return;
173 :
174 : // Create a lock file that is unique to this instance.
175 : UniqueLockFileName = LockFileName;
176 : UniqueLockFileName += "-%%%%%%%%";
177 : int UniqueLockFileID;
178 1760 : if (std::error_code EC = sys::fs::createUniqueFile(
179 1760 : UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) {
180 8 : std::string S("failed to create unique file ");
181 8 : S.append(UniqueLockFileName.str());
182 8 : setError(EC, S);
183 : return;
184 : }
185 :
186 : // Write our process ID to our unique lock file.
187 : {
188 : SmallString<256> HostID;
189 1752 : if (auto EC = getHostID(HostID)) {
190 0 : setError(EC, "failed to get host id");
191 0 : return;
192 : }
193 :
194 3504 : raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
195 : Out << HostID << ' ';
196 : #if LLVM_ON_UNIX
197 1752 : Out << getpid();
198 : #else
199 : Out << "1";
200 : #endif
201 1752 : Out.close();
202 :
203 1752 : if (Out.has_error()) {
204 : // We failed to write out PID, so report the error, remove the
205 : // unique lock file, and fail.
206 0 : std::string S("failed to write to ");
207 0 : S.append(UniqueLockFileName.str());
208 0 : setError(Out.error(), S);
209 0 : sys::fs::remove(UniqueLockFileName);
210 : return;
211 : }
212 : }
213 :
214 : // Clean up the unique file on signal, which also releases the lock if it is
215 : // held since the .lock symlink will point to a nonexistent file.
216 1752 : RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);
217 :
218 : while (true) {
219 : // Create a link from the lock file name. If this succeeds, we're done.
220 : std::error_code EC =
221 1752 : sys::fs::create_link(UniqueLockFileName, LockFileName);
222 1752 : if (!EC) {
223 : RemoveUniqueFile.lockAcquired();
224 1752 : return;
225 : }
226 :
227 : if (EC != errc::file_exists) {
228 0 : std::string S("failed to create link ");
229 0 : raw_string_ostream OSS(S);
230 0 : OSS << LockFileName.str() << " to " << UniqueLockFileName.str();
231 0 : setError(EC, OSS.str());
232 : return;
233 : }
234 :
235 : // Someone else managed to create the lock file first. Read the process ID
236 : // from the lock file.
237 0 : if ((Owner = readLockFile(LockFileName))) {
238 : // Wipe out our unique lock file (it's useless now)
239 0 : sys::fs::remove(UniqueLockFileName);
240 0 : return;
241 : }
242 :
243 0 : if (!sys::fs::exists(LockFileName)) {
244 : // The previous owner released the lock file before we could read it.
245 : // Try to get ownership again.
246 0 : continue;
247 : }
248 :
249 : // There is a lock file that nobody owns; try to clean it up and get
250 : // ownership.
251 0 : if ((EC = sys::fs::remove(LockFileName))) {
252 0 : std::string S("failed to remove lockfile ");
253 0 : S.append(UniqueLockFileName.str());
254 0 : setError(EC, S);
255 : return;
256 : }
257 : }
258 : }
259 :
260 3535 : LockFileManager::LockFileState LockFileManager::getState() const {
261 3535 : if (Owner)
262 : return LFS_Shared;
263 :
264 3521 : if (ErrorCode)
265 16 : return LFS_Error;
266 :
267 : return LFS_Owned;
268 : }
269 :
270 0 : std::string LockFileManager::getErrorMessage() const {
271 0 : if (ErrorCode) {
272 : std::string Str(ErrorDiagMsg);
273 : std::string ErrCodeMsg = ErrorCode.message();
274 0 : raw_string_ostream OSS(Str);
275 0 : if (!ErrCodeMsg.empty())
276 0 : OSS << ": " << ErrCodeMsg;
277 : return OSS.str();
278 : }
279 0 : return "";
280 : }
281 :
282 1752 : LockFileManager::~LockFileManager() {
283 1765 : if (getState() != LFS_Owned)
284 : return;
285 :
286 : // Since we own the lock, remove the lock file and our own unique lock file.
287 3504 : sys::fs::remove(LockFileName);
288 3504 : sys::fs::remove(UniqueLockFileName);
289 : // The unique file is now gone, so remove it from the signal handler. This
290 : // matches a sys::RemoveFileOnSignal() in LockFileManager().
291 1752 : sys::DontRemoveFileOnSignal(UniqueLockFileName);
292 1765 : }
293 :
294 4 : LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
295 4 : if (getState() != LFS_Shared)
296 : return Res_Success;
297 :
298 : #ifdef _WIN32
299 : unsigned long Interval = 1;
300 : #else
301 : struct timespec Interval;
302 4 : Interval.tv_sec = 0;
303 4 : Interval.tv_nsec = 1000000;
304 : #endif
305 : // Don't wait more than 40s per iteration. Total timeout for the file
306 : // to appear is ~1.5 minutes.
307 : const unsigned MaxSeconds = 40;
308 : do {
309 : // Sleep for the designated interval, to allow the owning process time to
310 : // finish up and remove the lock file.
311 : // FIXME: Should we hook in to system APIs to get a notification when the
312 : // lock file is deleted?
313 : #ifdef _WIN32
314 : Sleep(Interval);
315 : #else
316 52 : nanosleep(&Interval, nullptr);
317 : #endif
318 :
319 100 : if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
320 : errc::no_such_file_or_directory) {
321 : // If the original file wasn't created, somone thought the lock was dead.
322 4 : if (!sys::fs::exists(FileName))
323 : return Res_OwnerDied;
324 4 : return Res_Success;
325 : }
326 :
327 : // If the process owning the lock died without cleaning up, just bail out.
328 96 : if (!processStillExecuting((*Owner).first, (*Owner).second))
329 : return Res_OwnerDied;
330 :
331 : // Exponentially increase the time we wait for the lock to be removed.
332 : #ifdef _WIN32
333 : Interval *= 2;
334 : #else
335 48 : Interval.tv_sec *= 2;
336 48 : Interval.tv_nsec *= 2;
337 48 : if (Interval.tv_nsec >= 1000000000) {
338 4 : ++Interval.tv_sec;
339 4 : Interval.tv_nsec -= 1000000000;
340 : }
341 : #endif
342 : } while (
343 : #ifdef _WIN32
344 : Interval < MaxSeconds * 1000
345 : #else
346 48 : Interval.tv_sec < (time_t)MaxSeconds
347 : #endif
348 : );
349 :
350 : // Give up.
351 : return Res_Timeout;
352 : }
353 :
354 0 : std::error_code LockFileManager::unsafeRemoveLockFile() {
355 0 : return sys::fs::remove(LockFileName);
356 : }
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