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[lldb] Handle signals in a separate thread in the driver #134956

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Merged
merged 2 commits into from
Apr 10, 2025
Merged

[lldb] Handle signals in a separate thread in the driver #134956

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390942c
[lldb] Handle signals in a separate thread in the driver
JDevlieghere Apr 9, 2025
a2fae8b
Address Pavel's feedback
JDevlieghere Apr 10, 2025
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2 changes: 2 additions & 0 deletions lldb/tools/driver/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@ add_lldb_tool(lldb

LINK_LIBS
liblldb
lldbHost
lldbUtility

LINK_COMPONENTS
Option
Expand Down
96 changes: 62 additions & 34 deletions lldb/tools/driver/Driver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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"
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -636,15 +641,12 @@ void Driver::UpdateWindowSize() {
}
}

void sigwinch_handler(int signo) {
if (g_driver != nullptr)
g_driver->UpdateWindowSize();
}

void sigint_handler(int signo) {
#ifdef _WIN32 // Restore handler as it is not persistent on Windows
#ifdef _WIN32
// 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()) {
Expand All @@ -657,31 +659,6 @@ 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) {
std::string usage_str = tool_name.str() + " [options]";
table.printHelp(llvm::outs(), usage_str.c_str(), "LLDB", false);
Expand Down Expand Up @@ -787,11 +764,56 @@ int main(int argc, char const *argv[]) {
// Setup LLDB signal handlers once the debugger has been initialized.
SBDebugger::PrintDiagnosticsOnError();

// FIXME: Migrate the SIGINT handler to be handled by the signal loop below.
signal(SIGINT, sigint_handler);
#if !defined(_WIN32)
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 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;
Expand Down Expand Up @@ -824,5 +846,11 @@ 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;
}