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

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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.
This commit is contained in:
Jonas Devlieghere 2025-04-10 11:04:05 -07:00 committed by GitHub
parent 9102ccd2f7
commit 6493345c5a
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
2 changed files with 61 additions and 34 deletions
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2
lldb/tools/driver/CMakeLists.txt
View File

@ -22,6 +22,8 @@ add_lldb_tool(lldb
LINK_LIBS
liblldb
lldbHost
lldbUtility
LINK_COMPONENTS
Option

93
lldb/tools/driver/Driver.cpp
View File

@ -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 +641,12 @@ 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()) {
@ -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);
@ -787,11 +764,53 @@ 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 = {};
new_action.sa_handler = SIG_DFL;
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 +843,11 @@ 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;
}