Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
JDevlieghere merged 2 commits into from
Apr 10, 2025
Merged

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

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
390942c
[lldb] Handle signals in a separate thread in the driver
JDevlieghere Apr 9, 2025
a2fae8b
Address Pavel's feedback
JDevlieghere Apr 10, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions lldb/tools/driver/CMakeLists.txt
View file
Open in desktop
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
View file
Open in desktop
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;
}