https://github.com/JDevlieghere updated
https://github.com/llvm/llvm-project/pull/134956
>From 3943112f5182065eed43d72e2960ed166737b237 Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jo...@devlieghere.com>
Date: Tue, 8 Apr 2025 17:33:41 -0700
Subject: [PATCH] [lldb] Handle signals in a separate thread in the driver
Handle signals in a separate thread in the driver so that we can stop
worrying about signal safety of functions in libLLDB that may get called
from a signal handler.
---
lldb/tools/driver/CMakeLists.txt | 2 +
lldb/tools/driver/Driver.cpp | 117 ++++++++++++++++++++++---------
2 files changed, 84 insertions(+), 35 deletions(-)
diff --git a/lldb/tools/driver/CMakeLists.txt b/lldb/tools/driver/CMakeLists.txt
index 89884ecd0601b..8b4aa92f96f0d 100644
--- a/lldb/tools/driver/CMakeLists.txt
+++ b/lldb/tools/driver/CMakeLists.txt
@@ -22,6 +22,8 @@ add_lldb_tool(lldb
LINK_LIBS
liblldb
+ lldbHost
+ lldbUtility
LINK_COMPONENTS
Option
diff --git a/lldb/tools/driver/Driver.cpp b/lldb/tools/driver/Driver.cpp
index 15cb0134fec8e..2557c08c0e396 100644
--- a/lldb/tools/driver/Driver.cpp
+++ b/lldb/tools/driver/Driver.cpp
@@ -19,7 +19,9 @@
#include "lldb/API/SBStringList.h"
#include "lldb/API/SBStructuredData.h"
#include "lldb/Host/Config.h"
-
+#include "lldb/Host/MainLoop.h"
+#include "lldb/Host/MainLoopBase.h"
+#include "lldb/Utility/Status.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/InitLLVM.h"
@@ -50,6 +52,9 @@
using namespace lldb;
using namespace llvm;
+using lldb_private::MainLoop;
+using lldb_private::MainLoopBase;
+using lldb_private::Status;
namespace {
using namespace llvm::opt;
@@ -636,15 +641,11 @@ void Driver::UpdateWindowSize() {
}
}
-void sigwinch_handler(int signo) {
- if (g_driver != nullptr)
- g_driver->UpdateWindowSize();
-}
-
+#ifdef _WIN32
void sigint_handler(int signo) {
-#ifdef _WIN32 // Restore handler as it is not persistent on Windows
+ // Restore handler as it is not persistent on Windows.
signal(SIGINT, sigint_handler);
-#endif
+
static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;
if (g_driver != nullptr) {
if (!g_interrupt_sent.test_and_set()) {
@@ -656,30 +657,6 @@ void sigint_handler(int signo) {
_exit(signo);
}
-
-#ifndef _WIN32
-static void sigtstp_handler(int signo) {
- if (g_driver != nullptr)
- g_driver->GetDebugger().SaveInputTerminalState();
-
- // Unblock the signal and remove our handler.
- sigset_t set;
- sigemptyset(&set);
- sigaddset(&set, signo);
- pthread_sigmask(SIG_UNBLOCK, &set, nullptr);
- signal(signo, SIG_DFL);
-
- // Now re-raise the signal. We will immediately suspend...
- raise(signo);
- // ... and resume after a SIGCONT.
-
- // Now undo the modifications.
- pthread_sigmask(SIG_BLOCK, &set, nullptr);
- signal(signo, sigtstp_handler);
-
- if (g_driver != nullptr)
- g_driver->GetDebugger().RestoreInputTerminalState();
-}
#endif
static void printHelp(LLDBOptTable &table, llvm::StringRef tool_name) {
@@ -787,11 +764,75 @@ int main(int argc, char const *argv[]) {
// Setup LLDB signal handlers once the debugger has been initialized.
SBDebugger::PrintDiagnosticsOnError();
+#if defined(_WIN32)
+ // FIXME: Support signals in MainLoopWindows and handle SIGINT in the signal
+ // loop below.
signal(SIGINT, sigint_handler);
-#if !defined(_WIN32)
+#else
signal(SIGPIPE, SIG_IGN);
- signal(SIGWINCH, sigwinch_handler);
- signal(SIGTSTP, sigtstp_handler);
+
+ // Handle signals in a MainLoop running on a separate thread.
+ MainLoop signal_loop;
+ Status signal_status;
+
+ auto sigint_handler = signal_loop.RegisterSignal(
+ SIGINT,
+ [&](MainLoopBase &loop) {
+ static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;
+ if (g_driver) {
+ if (!g_interrupt_sent.test_and_set()) {
+ g_driver->GetDebugger().DispatchInputInterrupt();
+ g_interrupt_sent.clear();
+ return;
+ }
+ }
+ loop.RequestTermination();
+ _exit(SIGINT);
+ },
+ signal_status);
+ assert(sigint_handler && signal_status.Success());
+
+ auto sigwinch_handler = signal_loop.RegisterSignal(
+ SIGWINCH,
+ [&](MainLoopBase &) {
+ if (g_driver)
+ g_driver->UpdateWindowSize();
+ },
+ signal_status);
+ assert(sigwinch_handler && signal_status.Success());
+
+ auto sigtstp_handler = signal_loop.RegisterSignal(
+ SIGTSTP,
+ [&](MainLoopBase &) {
+ if (g_driver)
+ g_driver->GetDebugger().SaveInputTerminalState();
+
+ struct sigaction old_action;
+ struct sigaction new_action;
+
+ memset(&new_action, 0, sizeof(new_action));
+ new_action.sa_handler = SIG_DFL;
+ new_action.sa_flags = SA_SIGINFO;
+ sigemptyset(&new_action.sa_mask);
+ sigaddset(&new_action.sa_mask, SIGTSTP);
+
+ int ret = sigaction(SIGTSTP, &new_action, &old_action);
+ UNUSED_IF_ASSERT_DISABLED(ret);
+ assert(ret == 0 && "sigaction failed");
+
+ raise(SIGTSTP);
+
+ ret = sigaction(SIGTSTP, &old_action, nullptr);
+ UNUSED_IF_ASSERT_DISABLED(ret);
+ assert(ret == 0 && "sigaction failed");
+
+ if (g_driver)
+ g_driver->GetDebugger().RestoreInputTerminalState();
+ },
+ signal_status);
+ assert(sigtstp_handler && signal_status.Success());
+
+ std::thread signal_thread([&] { signal_loop.Run(); });
#endif
int exit_code = 0;
@@ -824,5 +865,11 @@ int main(int argc, char const *argv[]) {
future.wait();
}
+#if !defined(_WIN32)
+ signal_loop.AddPendingCallback(
+ [](MainLoopBase &loop) { loop.RequestTermination(); });
+ signal_thread.join();
+#endif
+
return exit_code;
}
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