228f66807d
These are identified by misc-include-cleaner. I've filtered out those that break builds. Also, I'm staying away from llvm-config.h, config.h, and Compiler.h, which likely cause platform- or compiler-specific build failures.
293 lines
9.5 KiB
C++
293 lines
9.5 KiB
C++
//===--- LockFileManager.cpp - File-level Locking Utility------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/LockFileManager.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
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#include "llvm/Support/Errc.h"
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#include "llvm/Support/ErrorOr.h"
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#include "llvm/Support/ExponentialBackoff.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/Process.h"
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#include "llvm/Support/Signals.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cerrno>
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#include <chrono>
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#include <ctime>
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#include <memory>
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#include <system_error>
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#include <tuple>
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#ifdef _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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#if defined(__APPLE__) && defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ > 1050)
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#define USE_OSX_GETHOSTUUID 1
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#else
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#define USE_OSX_GETHOSTUUID 0
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#endif
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#if USE_OSX_GETHOSTUUID
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#include <uuid/uuid.h>
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#endif
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using namespace llvm;
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/// 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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std::optional<LockFileManager::OwnedByAnother>
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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 std::nullopt;
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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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OwnedByAnother Owner;
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Owner.OwnerHostName = Hostname;
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Owner.OwnerPID = PID;
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if (processStillExecuting(Owner.OwnerHostName, Owner.OwnerPID))
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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 std::nullopt;
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}
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static std::error_code getHostID(SmallVectorImpl<char> &HostID) {
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HostID.clear();
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#if USE_OSX_GETHOSTUUID
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// On OS X, use the more stable hardware UUID instead of hostname.
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struct timespec wait = {1, 0}; // 1 second.
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uuid_t uuid;
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if (gethostuuid(uuid, &wait) != 0)
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return errnoAsErrorCode();
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uuid_string_t UUIDStr;
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uuid_unparse(uuid, UUIDStr);
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StringRef UUIDRef(UUIDStr);
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HostID.append(UUIDRef.begin(), UUIDRef.end());
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#elif LLVM_ON_UNIX
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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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StringRef HostNameRef(HostName);
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HostID.append(HostNameRef.begin(), HostNameRef.end());
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#else
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StringRef Dummy("localhost");
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HostID.append(Dummy.begin(), Dummy.end());
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#endif
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return std::error_code();
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}
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bool LockFileManager::processStillExecuting(StringRef HostID, int PID) {
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#if LLVM_ON_UNIX && !defined(__ANDROID__)
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SmallString<256> StoredHostID;
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if (getHostID(StoredHostID))
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return true; // Conservatively assume it's executing on error.
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// Check whether the process is dead. If so, we're done.
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if (StoredHostID == HostID && 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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namespace {
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/// An RAII helper object ensure that the unique lock file is removed.
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///
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/// Ensures that if there is an error or a signal before we finish acquiring the
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/// lock, the unique file will be removed. And if we successfully take the lock,
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/// the signal handler is left in place so that signals while the lock is held
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/// will remove the unique lock file. The caller should ensure there is a
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/// matching call to sys::DontRemoveFileOnSignal when the lock is released.
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class RemoveUniqueLockFileOnSignal {
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StringRef Filename;
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bool RemoveImmediately;
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public:
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RemoveUniqueLockFileOnSignal(StringRef Name)
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: Filename(Name), RemoveImmediately(true) {
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sys::RemoveFileOnSignal(Filename, nullptr);
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}
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~RemoveUniqueLockFileOnSignal() {
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if (!RemoveImmediately) {
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// Leave the signal handler enabled. It will be removed when the lock is
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// released.
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return;
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}
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sys::fs::remove(Filename);
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sys::DontRemoveFileOnSignal(Filename);
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}
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void lockAcquired() { RemoveImmediately = false; }
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};
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} // end anonymous namespace
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LockFileManager::LockFileManager(StringRef FileName)
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: FileName(FileName), Owner(OwnerUnknown{}) {}
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Expected<bool> LockFileManager::tryLock() {
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assert(std::holds_alternative<OwnerUnknown>(Owner) &&
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"lock has already been attempted");
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SmallString<128> AbsoluteFileName(FileName);
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if (std::error_code EC = sys::fs::make_absolute(AbsoluteFileName))
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return createStringError(EC, "failed to obtain absolute path for " +
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AbsoluteFileName);
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LockFileName = AbsoluteFileName;
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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 (auto LockFileOwner = readLockFile(LockFileName)) {
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Owner = std::move(*LockFileOwner);
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return false;
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}
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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, UniqueLockFileID, UniqueLockFileName))
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return createStringError(EC, "failed to create unique file " +
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UniqueLockFileName);
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// Clean up the unique file on signal or scope exit.
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RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);
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// Write our process ID to our unique lock file.
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{
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SmallString<256> HostID;
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if (auto EC = getHostID(HostID))
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return createStringError(EC, "failed to get host id");
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raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
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Out << HostID << ' ' << sys::Process::getProcessId();
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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 report the error and fail.
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Error Err = createStringError(Out.error(),
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"failed to write to " + UniqueLockFileName);
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// Don't call report_fatal_error.
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Out.clear_error();
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return std::move(Err);
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}
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}
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while (true) {
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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, LockFileName);
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if (!EC) {
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RemoveUniqueFile.lockAcquired();
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Owner = OwnedByUs{};
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return true;
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}
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if (EC != errc::file_exists)
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return createStringError(EC, "failed to create link " + LockFileName +
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" to " + UniqueLockFileName);
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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 (auto LockFileOwner = readLockFile(LockFileName)) {
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Owner = std::move(*LockFileOwner);
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return false;
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}
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if (!sys::fs::exists(LockFileName)) {
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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)))
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return createStringError(EC, "failed to remove lockfile " +
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UniqueLockFileName);
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}
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}
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LockFileManager::~LockFileManager() {
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if (!std::holds_alternative<OwnedByUs>(Owner))
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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);
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sys::fs::remove(UniqueLockFileName);
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// The unique file is now gone, so remove it from the signal handler. This
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// matches a sys::RemoveFileOnSignal() in LockFileManager().
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sys::DontRemoveFileOnSignal(UniqueLockFileName);
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}
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WaitForUnlockResult
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LockFileManager::waitForUnlockFor(std::chrono::seconds MaxSeconds) {
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auto *LockFileOwner = std::get_if<OwnedByAnother>(&Owner);
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assert(LockFileOwner &&
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"waiting for lock to be unlocked without knowing the owner");
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// Since we don't yet have an event-based method to wait for the lock file,
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// use randomized exponential backoff, similar to Ethernet collision
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// algorithm. This improves performance on machines with high core counts
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// when the file lock is heavily contended by multiple clang processes
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using namespace std::chrono_literals;
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ExponentialBackoff Backoff(MaxSeconds, 10ms, 500ms);
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// Wait first as this is only called when the lock is known to be held.
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while (Backoff.waitForNextAttempt()) {
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// FIXME: implement event-based waiting
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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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return WaitForUnlockResult::Success;
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// If the process owning the lock died without cleaning up, just bail out.
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if (!processStillExecuting(LockFileOwner->OwnerHostName,
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LockFileOwner->OwnerPID))
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return WaitForUnlockResult::OwnerDied;
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}
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// Give up.
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return WaitForUnlockResult::Timeout;
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}
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std::error_code LockFileManager::unsafeMaybeUnlock() {
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return sys::fs::remove(LockFileName);
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}
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