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//===--- Shutdown.h - Unclean exit scenarios --------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// LSP specifies a protocol for shutting down: a `shutdown` request followed
// by an `exit` notification. If this protocol is followed, clangd should
// finish outstanding work and exit with code 0.
// The way this works in the happy case:
// - when ClangdLSPServer gets `shutdown`, it sets a flag
// - when ClangdLSPServer gets `exit`, it returns false to indicate end-of-LSP
// - Transport::loop() returns with no error
// - ClangdServer::run() checks the shutdown flag and returns with no error.
// - we `return 0` from main()
// - destructor of ClangdServer and other main()-locals runs.
// This blocks until outstanding requests complete (results are ignored)
// - global destructors run, such as fallback deletion of temporary files
// There are a number of things that can go wrong. Some are handled here, and
// some elsewhere.
// - `exit` notification with no `shutdown`:
// ClangdServer::run() sees this and returns false, main() returns nonzero.
// - stdin/stdout are closed
// The Transport detects this while doing IO and returns an error from loop()
// ClangdServer::run() logs a message and then returns false, etc
// - a request thread gets stuck, so the ClangdServer destructor hangs.
// Before returning from main(), we start a watchdog thread to abort() the
// process if it takes too long to exit. See abortAfterTimeout().
// - clangd crashes (e.g. segfault or assertion)
// A fatal signal is sent (SEGV, ABRT, etc)
// The installed signal handler prints a stack trace and exits.
// - parent process goes away or tells us to shut down
// A "graceful shutdown" signal is sent (TERM, HUP, etc).
// The installed signal handler calls requestShutdown() which sets a flag.
// The Transport IO is interrupted, and Transport::loop() checks the flag and
// returns an error, etc.
#include <cerrno>
#include <chrono>
namespace clang {
namespace clangd {
/// Causes this process to crash if still running after Timeout.
void abortAfterTimeout(std::chrono::seconds Timeout);
/// Sets a flag to indicate that clangd was sent a shutdown signal, and the
/// transport loop should exit at the next opportunity.
/// If shutdown was already requested, aborts the process.
/// This function is threadsafe and signal-safe.
void requestShutdown();
/// Checks whether requestShutdown() was called.
/// This function is threadsafe and signal-safe.
bool shutdownRequested();
/// Retry an operation if it gets interrupted by a signal.
/// This is like llvm::sys::RetryAfterSignal, except that if shutdown was
/// requested (which interrupts IO), we'll fail rather than retry.
template <typename Fun, typename Ret = decltype(std::declval<Fun>()())>
Ret retryAfterSignalUnlessShutdown(
const std::enable_if_t<true, Ret> &Fail, // Suppress deduction.
const Fun &F) {
Ret Res;
do {
if (shutdownRequested())
return Fail;
errno = 0;
Res = F();
} while (Res == Fail && errno == EINTR);
return Res;
} // namespace clangd
} // namespace clang