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