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045695f85c
Motivation: At the moment it is hard to attribute a clangd crash to a specific request out of all in-flight requests that might be processed concurrently. So before we can act on production clangd crashes, we have to do quite some digging through the log tables populated by our in-house VSCode extension or sometimes even directly reach out to the affected developer. Having all the details needed to reproduce a crash printed alongside its stack trace has a potential to save us quite some time, that could better be spent on fixing the actual problems. Implementation approach: * introduce `ThreadCrashReporter` class that allows to set a temporary signal handler for the current thread * follow RAII pattern to simplify printing context for crashes occurring within a particular scope * hold `std::function` as a handler to allow capturing context to print * set local `ThreadCrashReporter` within `JSONTransport::loop()` to print request JSON for main thread crashes, and in `ASTWorker::run()` to print the file paths, arguments and contents for worker thread crashes `ThreadCrashReporter` currently allows only one active handler per thread, but the approach can be extended to support stacked handlers printing context incrementally. Example output for main thread crashes: ``` ... #15 0x00007f7ddc819493 __libc_start_main (/lib64/libc.so.6+0x23493) #16 0x000000000249775e _start (/home/emmablink/local/llvm-project/build/bin/clangd+0x249775e) Signalled while processing message: {"jsonrpc": "2.0", "method": "textDocument/didOpen", "params": {"textDocument": {"uri": "file:///home/emmablink/test.cpp", "languageId": "cpp", "version": 1, "text": "template <typename>\nclass Bar {\n Bar<int> *variables_to_modify;\n foo() {\n for (auto *c : *variables_to_modify)\n delete c;\n }\n};\n"}}} ``` Example output for AST worker crashes: ``` ... #41 0x00007fb18304c14a start_thread pthread_create.c:0:0 #42 0x00007fb181bfcdc3 clone (/lib64/libc.so.6+0xfcdc3) Signalled during AST action: Filename: test.cpp Directory: /home/emmablink Command Line: /usr/bin/clang -resource-dir=/data/users/emmablink/llvm-project/build/lib/clang/14.0.0 -- /home/emmablink/test.cpp Version: 1 Contents: template <typename> class Bar { Bar<int> *variables_to_modify; foo() { for (auto *c : *variables_to_modify) delete c; } }; ``` Testing: The unit test covers the thread-localitity and nesting aspects of `ThreadCrashReporter`. There might be way to set up a lit-based integration test that would spawn clangd, send a message to it, signal it immediately and check the standard output, but this might be prone to raceconditions. Reviewed By: sammccall Differential Revision: https://reviews.llvm.org/D109506
79 lines
2.2 KiB
C++
79 lines
2.2 KiB
C++
///===- ThreadCrashReporterTests.cpp - Thread local signal handling tests -===//
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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 "support/ThreadCrashReporter.h"
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#include "support/Threading.h"
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#include "llvm/Support/Signals.h"
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#include "gtest/gtest.h"
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#include <csignal>
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#include <string>
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namespace clang {
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namespace clangd {
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namespace {
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static void infoSignalHandler() { ThreadCrashReporter::runCrashHandlers(); }
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TEST(ThreadCrashReporterTest, All) {
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#if defined(_WIN32)
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// Simulate signals on Windows for unit testing purposes.
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// The `crash.test` lit test checks the end-to-end integration.
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auto SignalCurrentThread = []() { infoSignalHandler(); };
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#else
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llvm::sys::SetInfoSignalFunction(&infoSignalHandler);
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auto SignalCurrentThread = []() { raise(SIGUSR1); };
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#endif
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AsyncTaskRunner Runner;
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auto SignalAnotherThread = [&]() {
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Runner.runAsync("signal another thread", SignalCurrentThread);
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Runner.wait();
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};
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bool Called;
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{
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ThreadCrashReporter ScopedReporter([&Called]() { Called = true; });
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// Check handler gets called when a signal gets delivered to the current
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// thread.
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Called = false;
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SignalCurrentThread();
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EXPECT_TRUE(Called);
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// Check handler does not get called when another thread gets signalled.
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Called = false;
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SignalAnotherThread();
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EXPECT_FALSE(Called);
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}
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// Check handler does not get called when the reporter object goes out of
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// scope.
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Called = false;
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SignalCurrentThread();
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EXPECT_FALSE(Called);
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std::string Order = "";
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{
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ThreadCrashReporter ScopedReporter([&Order] { Order.push_back('a'); });
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{
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ThreadCrashReporter ScopedReporter([&Order] { Order.push_back('b'); });
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SignalCurrentThread();
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}
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// Check that handlers are called in LIFO order.
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EXPECT_EQ(Order, "ba");
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// Check that current handler is the only one after the nested scope is
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// over.
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SignalCurrentThread();
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EXPECT_EQ(Order, "baa");
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}
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}
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} // namespace
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} // namespace clangd
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} // namespace clang
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