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1//===--- Shutdown.h - Unclean exit scenarios --------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// LSP specifies a protocol for shutting down: a `shutdown` request followed10// by an `exit` notification. If this protocol is followed, clangd should11// finish outstanding work and exit with code 0.12//13// The way this works in the happy case:14// - when ClangdLSPServer gets `shutdown`, it sets a flag15// - when ClangdLSPServer gets `exit`, it returns false to indicate end-of-LSP16// - Transport::loop() returns with no error17// - ClangdServer::run() checks the shutdown flag and returns with no error.18// - we `return 0` from main()19// - destructor of ClangdServer and other main()-locals runs.20// This blocks until outstanding requests complete (results are ignored)21// - global destructors run, such as fallback deletion of temporary files22//23// There are a number of things that can go wrong. Some are handled here, and24// some elsewhere.25// - `exit` notification with no `shutdown`:26// ClangdServer::run() sees this and returns false, main() returns nonzero.27// - stdin/stdout are closed28// The Transport detects this while doing IO and returns an error from loop()29// ClangdServer::run() logs a message and then returns false, etc30// - a request thread gets stuck, so the ClangdServer destructor hangs.31// Before returning from main(), we start a watchdog thread to abort() the32// process if it takes too long to exit. See abortAfterTimeout().33// - clangd crashes (e.g. segfault or assertion)34// A fatal signal is sent (SEGV, ABRT, etc)35// The installed signal handler prints a stack trace and exits.36// - parent process goes away or tells us to shut down37// A "graceful shutdown" signal is sent (TERM, HUP, etc).38// The installed signal handler calls requestShutdown() which sets a flag.39// The Transport IO is interrupted, and Transport::loop() checks the flag and40// returns an error, etc.41//42//===----------------------------------------------------------------------===//43#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_SUPPORT_SHUTDOWN_H44#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_SUPPORT_SHUTDOWN_H45 46#include <cerrno>47#include <chrono>48#include <type_traits>49#include <utility>50 51namespace clang {52namespace clangd {53 54/// Causes this process to crash if still running after Timeout.55void abortAfterTimeout(std::chrono::seconds Timeout);56 57/// Sets a flag to indicate that clangd was sent a shutdown signal, and the58/// transport loop should exit at the next opportunity.59/// If shutdown was already requested, aborts the process.60/// This function is threadsafe and signal-safe.61void requestShutdown();62/// Checks whether requestShutdown() was called.63/// This function is threadsafe and signal-safe.64bool shutdownRequested();65 66/// Retry an operation if it gets interrupted by a signal.67/// This is like llvm::sys::RetryAfterSignal, except that if shutdown was68/// requested (which interrupts IO), we'll fail rather than retry.69template <typename Fun, typename Ret = decltype(std::declval<Fun>()())>70Ret retryAfterSignalUnlessShutdown(71 const std::enable_if_t<true, Ret> &Fail, // Suppress deduction.72 const Fun &F) {73 Ret Res;74 do {75 if (shutdownRequested())76 return Fail;77 errno = 0;78 Res = F();79 } while (Res == Fail && errno == EINTR);80 return Res;81}82 83} // namespace clangd84} // namespace clang85 86#endif87