mirror of
https://github.com/c64scene-ar/llvm-6502.git
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The main difference is the removal of std::error_code exists(const Twine &path, bool &result); It was an horribly redundant interface since a file not existing is also a valid error_code. Now we have an access function that returns just an error_code. This is the only function that has to be implemented for Unix and Windows. The functions can_write, exists and can_execute an now just wrappers. One still has to be very careful using these function to avoid introducing race conditions (Time of check to time of use). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217625 91177308-0d34-0410-b5e6-96231b3b80d8
266 lines
7.3 KiB
C++
266 lines
7.3 KiB
C++
//===--- LockFileManager.cpp - File-level Locking Utility------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/LockFileManager.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Support/Errc.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/Path.h"
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#include "llvm/Support/raw_ostream.h"
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#include <sys/stat.h>
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#include <sys/types.h>
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#if LLVM_ON_WIN32
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#include <windows.h>
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#endif
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#if LLVM_ON_UNIX
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#include <unistd.h>
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#endif
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using namespace llvm;
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/// \brief Attempt to read the lock file with the given name, if it exists.
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///
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/// \param LockFileName The name of the lock file to read.
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///
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/// \returns The process ID of the process that owns this lock file
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Optional<std::pair<std::string, int> >
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LockFileManager::readLockFile(StringRef LockFileName) {
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// Read the owning host and PID out of the lock file. If it appears that the
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// owning process is dead, the lock file is invalid.
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ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
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MemoryBuffer::getFile(LockFileName);
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if (!MBOrErr) {
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sys::fs::remove(LockFileName);
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return None;
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}
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MemoryBuffer &MB = *MBOrErr.get();
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StringRef Hostname;
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StringRef PIDStr;
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std::tie(Hostname, PIDStr) = getToken(MB.getBuffer(), " ");
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PIDStr = PIDStr.substr(PIDStr.find_first_not_of(" "));
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int PID;
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if (!PIDStr.getAsInteger(10, PID)) {
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auto Owner = std::make_pair(std::string(Hostname), PID);
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if (processStillExecuting(Owner.first, Owner.second))
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return Owner;
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}
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// Delete the lock file. It's invalid anyway.
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sys::fs::remove(LockFileName);
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return None;
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}
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bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) {
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#if LLVM_ON_UNIX && !defined(__ANDROID__)
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char MyHostname[256];
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MyHostname[255] = 0;
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MyHostname[0] = 0;
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gethostname(MyHostname, 255);
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// Check whether the process is dead. If so, we're done.
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if (MyHostname == Hostname && getsid(PID) == -1 && errno == ESRCH)
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return false;
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#endif
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return true;
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}
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LockFileManager::LockFileManager(StringRef FileName)
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{
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this->FileName = FileName;
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if (std::error_code EC = sys::fs::make_absolute(this->FileName)) {
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Error = EC;
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return;
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}
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LockFileName = this->FileName;
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LockFileName += ".lock";
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// If the lock file already exists, don't bother to try to create our own
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// lock file; it won't work anyway. Just figure out who owns this lock file.
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if ((Owner = readLockFile(LockFileName)))
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return;
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// Create a lock file that is unique to this instance.
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UniqueLockFileName = LockFileName;
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UniqueLockFileName += "-%%%%%%%%";
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int UniqueLockFileID;
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if (std::error_code EC = sys::fs::createUniqueFile(
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UniqueLockFileName.str(), UniqueLockFileID, UniqueLockFileName)) {
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Error = EC;
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return;
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}
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// Write our process ID to our unique lock file.
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{
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raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
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#if LLVM_ON_UNIX
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// FIXME: move getpid() call into LLVM
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char hostname[256];
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hostname[255] = 0;
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hostname[0] = 0;
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gethostname(hostname, 255);
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Out << hostname << ' ' << getpid();
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#else
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Out << "localhost 1";
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#endif
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Out.close();
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if (Out.has_error()) {
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// We failed to write out PID, so make up an excuse, remove the
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// unique lock file, and fail.
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Error = make_error_code(errc::no_space_on_device);
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sys::fs::remove(UniqueLockFileName.c_str());
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return;
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}
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}
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while (1) {
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// Create a link from the lock file name. If this succeeds, we're done.
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std::error_code EC =
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sys::fs::create_link(UniqueLockFileName.str(), LockFileName.str());
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if (!EC)
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return;
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if (EC != errc::file_exists) {
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Error = EC;
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return;
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}
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// Someone else managed to create the lock file first. Read the process ID
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// from the lock file.
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if ((Owner = readLockFile(LockFileName))) {
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// Wipe out our unique lock file (it's useless now)
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sys::fs::remove(UniqueLockFileName.str());
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return;
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}
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if (!sys::fs::exists(LockFileName.str())) {
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// The previous owner released the lock file before we could read it.
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// Try to get ownership again.
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continue;
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}
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// There is a lock file that nobody owns; try to clean it up and get
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// ownership.
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if ((EC = sys::fs::remove(LockFileName.str()))) {
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Error = EC;
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return;
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}
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}
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}
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LockFileManager::LockFileState LockFileManager::getState() const {
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if (Owner)
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return LFS_Shared;
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if (Error)
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return LFS_Error;
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return LFS_Owned;
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}
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LockFileManager::~LockFileManager() {
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if (getState() != LFS_Owned)
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return;
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// Since we own the lock, remove the lock file and our own unique lock file.
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sys::fs::remove(LockFileName.str());
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sys::fs::remove(UniqueLockFileName.str());
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}
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LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
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if (getState() != LFS_Shared)
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return Res_Success;
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#if LLVM_ON_WIN32
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unsigned long Interval = 1;
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#else
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struct timespec Interval;
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Interval.tv_sec = 0;
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Interval.tv_nsec = 1000000;
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#endif
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// Don't wait more than five minutes for the file to appear.
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unsigned MaxSeconds = 300;
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bool LockFileGone = false;
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do {
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// Sleep for the designated interval, to allow the owning process time to
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// finish up and remove the lock file.
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// FIXME: Should we hook in to system APIs to get a notification when the
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// lock file is deleted?
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#if LLVM_ON_WIN32
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Sleep(Interval);
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#else
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nanosleep(&Interval, nullptr);
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#endif
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bool LockFileJustDisappeared = false;
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// If the lock file is still expected to be there, check whether it still
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// is.
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if (!LockFileGone) {
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if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
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errc::no_such_file_or_directory) {
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LockFileGone = true;
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LockFileJustDisappeared = true;
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}
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}
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// If the lock file is no longer there, check if the original file is
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// available now.
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if (LockFileGone) {
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if (sys::fs::exists(FileName.str())) {
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return Res_Success;
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}
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// The lock file is gone, so now we're waiting for the original file to
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// show up. If this just happened, reset our waiting intervals and keep
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// waiting.
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if (LockFileJustDisappeared) {
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MaxSeconds = 5;
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#if LLVM_ON_WIN32
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Interval = 1;
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#else
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Interval.tv_sec = 0;
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Interval.tv_nsec = 1000000;
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#endif
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continue;
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}
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}
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// If we're looking for the lock file to disappear, but the process
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// owning the lock died without cleaning up, just bail out.
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if (!LockFileGone &&
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!processStillExecuting((*Owner).first, (*Owner).second)) {
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return Res_OwnerDied;
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}
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// Exponentially increase the time we wait for the lock to be removed.
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#if LLVM_ON_WIN32
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Interval *= 2;
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#else
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Interval.tv_sec *= 2;
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Interval.tv_nsec *= 2;
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if (Interval.tv_nsec >= 1000000000) {
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++Interval.tv_sec;
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Interval.tv_nsec -= 1000000000;
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}
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#endif
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} while (
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#if LLVM_ON_WIN32
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Interval < MaxSeconds * 1000
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#else
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Interval.tv_sec < (time_t)MaxSeconds
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#endif
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);
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// Give up.
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return Res_Timeout;
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}
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