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LibCore: Harden signal handling code to be called in global destrcutors

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Move some more complex globals into a Singleton, which allows it being
used from global destructors. It solves problems where some global
variables, such as HashMaps may already be deleted, triggering crashes
trying to use them.
This commit is contained in:
Tom 2021-01-08 12:09:39 -07:00 committed by Andreas Kling
parent 1fc7d65aad
commit 21e6f5176c
Notes: sideshowbarker 2024-07-18 23:58:52 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/21e6f5176c3
Pull-request: https://github.com/SerenityOS/serenity/pull/4854
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/alimpfard
2 changed files with 79 additions and 65 deletions
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99
Libraries/LibCore/EventLoop.cpp
View File

@ -30,6 +30,7 @@
#include <AK/JsonObject.h>
#include <AK/JsonValue.h>
#include <AK/NeverDestroyed.h>
#include <AK/Singleton.h>
#include <AK/TemporaryChange.h>
#include <AK/Time.h>
#include <LibCore/Event.h>
@ -82,12 +83,65 @@ static NeverDestroyed<IDAllocator> s_id_allocator;
static HashMap<int, NonnullOwnPtr<EventLoopTimer>>* s_timers;
static HashTable<Notifier*>* s_notifiers;
int EventLoop::s_wake_pipe_fds[2];
HashMap<int, NonnullRefPtr<EventLoop::SignalHandlers>> EventLoop::s_signal_handlers;
int EventLoop::s_next_signal_id = 0;
pid_t EventLoop::s_pid;
static RefPtr<LocalServer> s_rpc_server;
HashMap<int, RefPtr<RPCClient>> s_rpc_clients;
class SignalHandlers : public RefCounted<SignalHandlers> {
AK_MAKE_NONCOPYABLE(SignalHandlers);
AK_MAKE_NONMOVABLE(SignalHandlers);
public:
SignalHandlers(int signo, void (*handle_signal)(int));
~SignalHandlers();
void dispatch();
int add(Function<void(int)>&& handler);
bool remove(int handler_id);
bool is_empty() const
{
if (m_calling_handlers) {
for (auto& handler : m_handlers_pending) {
if (handler.value)
return false; // an add is pending
}
}
return m_handlers.is_empty();
}
bool have(int handler_id) const
{
if (m_calling_handlers) {
auto it = m_handlers_pending.find(handler_id);
if (it != m_handlers_pending.end()) {
if (!it->value)
return false; // a deletion is pending
}
}
return m_handlers.contains(handler_id);
}
int m_signo;
void (*m_original_handler)(int); // TODO: can't use sighandler_t?
HashMap<int, Function<void(int)>> m_handlers;
HashMap<int, Function<void(int)>> m_handlers_pending;
bool m_calling_handlers { false };
};
struct SignalHandlersInfo {
HashMap<int, NonnullRefPtr<SignalHandlers>> signal_handlers;
int next_signal_id { 0 };
};
template<bool create_if_null = true>
inline SignalHandlersInfo* signals_info()
{
static SignalHandlersInfo* s_signals;
return AK::Singleton<SignalHandlersInfo>::get(s_signals);
}
pid_t EventLoop::s_pid;
class RPCClient : public Object {
C_OBJECT(RPCClient)
public:
@ -416,16 +470,16 @@ void EventLoop::post_event(Object& receiver, NonnullOwnPtr<Event>&& event)
m_queued_events.empend(receiver, move(event));
}
EventLoop::SignalHandlers::SignalHandlers(int signo)
SignalHandlers::SignalHandlers(int signo, void (*handle_signal)(int))
: m_signo(signo)
, m_original_handler(signal(signo, EventLoop::handle_signal))
, m_original_handler(signal(signo, handle_signal))
{
#ifdef EVENTLOOP_DEBUG
dbgln("Core::EventLoop: Registered handler for signal {}", m_signo);
#endif
}
EventLoop::SignalHandlers::~SignalHandlers()
SignalHandlers::~SignalHandlers()
{
#ifdef EVENTLOOP_DEBUG
dbgln("Core::EventLoop: Unregistering handler for signal {}", m_signo);
@ -433,7 +487,7 @@ EventLoop::SignalHandlers::~SignalHandlers()
signal(m_signo, m_original_handler);
}
void EventLoop::SignalHandlers::dispatch()
void SignalHandlers::dispatch()
{
TemporaryChange change(m_calling_handlers, true);
for (auto& handler : m_handlers)
@ -452,9 +506,9 @@ void EventLoop::SignalHandlers::dispatch()
}
}
int EventLoop::SignalHandlers::add(Function<void(int)>&& handler)
int SignalHandlers::add(Function<void(int)>&& handler)
{
int id = ++EventLoop::s_next_signal_id; // TODO: worry about wrapping and duplicates?
int id = ++signals_info()->next_signal_id; // TODO: worry about wrapping and duplicates?
if (m_calling_handlers)
m_handlers_pending.set(id, move(handler));
else
@ -462,7 +516,7 @@ int EventLoop::SignalHandlers::add(Function<void(int)>&& handler)
return id;
}
bool EventLoop::SignalHandlers::remove(int handler_id)
bool SignalHandlers::remove(int handler_id)
{
ASSERT(handler_id != 0);
if (m_calling_handlers) {
@ -486,8 +540,9 @@ bool EventLoop::SignalHandlers::remove(int handler_id)
void EventLoop::dispatch_signal(int signo)
{
auto handlers = s_signal_handlers.find(signo);
if (handlers != s_signal_handlers.end()) {
auto& info = *signals_info();
auto handlers = info.signal_handlers.find(signo);
if (handlers != info.signal_handlers.end()) {
// Make sure we bump the ref count while dispatching the handlers!
// This allows a handler to unregister/register while the handlers
// are being called!
@ -520,11 +575,12 @@ void EventLoop::handle_signal(int signo)
int EventLoop::register_signal(int signo, Function<void(int)> handler)
{
ASSERT(signo != 0);
auto handlers = s_signal_handlers.find(signo);
if (handlers == s_signal_handlers.end()) {
auto signal_handlers = adopt(*new SignalHandlers(signo));
auto& info = *signals_info();
auto handlers = info.signal_handlers.find(signo);
if (handlers == info.signal_handlers.end()) {
auto signal_handlers = adopt(*new SignalHandlers(signo, EventLoop::handle_signal));
auto handler_id = signal_handlers->add(move(handler));
s_signal_handlers.set(signo, move(signal_handlers));
info.signal_handlers.set(signo, move(signal_handlers));
return handler_id;
} else {
return handlers->value->add(move(handler));
@ -535,7 +591,8 @@ void EventLoop::unregister_signal(int handler_id)
{
ASSERT(handler_id != 0);
int remove_signo = 0;
for (auto& h : s_signal_handlers) {
auto& info = *signals_info();
for (auto& h : info.signal_handlers) {
auto& handlers = *h.value;
if (handlers.remove(handler_id)) {
if (handlers.is_empty())
@ -544,7 +601,7 @@ void EventLoop::unregister_signal(int handler_id)
}
}
if (remove_signo != 0)
s_signal_handlers.remove(remove_signo);
info.signal_handlers.remove(remove_signo);
}
void EventLoop::notify_forked(ForkEvent event)
@ -555,8 +612,10 @@ void EventLoop::notify_forked(ForkEvent event)
s_event_loop_stack->clear();
s_timers->clear();
s_notifiers->clear();
s_signal_handlers.clear();
s_next_signal_id = 0;
if (auto* info = signals_info<false>()) {
info->signal_handlers.clear();
info->next_signal_id = 0;
}
s_pid = 0;
s_rpc_server = nullptr;
s_rpc_clients.clear();

45
Libraries/LibCore/EventLoop.h
View File

@ -107,52 +107,7 @@ private:
NonnullOwnPtr<Event> event;
};
class SignalHandlers : public RefCounted<SignalHandlers> {
AK_MAKE_NONCOPYABLE(SignalHandlers);
AK_MAKE_NONMOVABLE(SignalHandlers);
public:
SignalHandlers(int signo);
~SignalHandlers();
void dispatch();
int add(Function<void(int)>&& handler);
bool remove(int handler_id);
bool is_empty() const
{
if (m_calling_handlers) {
for (auto& handler : m_handlers_pending) {
if (handler.value)
return false; // an add is pending
}
}
return m_handlers.is_empty();
}
bool have(int handler_id) const
{
if (m_calling_handlers) {
auto it = m_handlers_pending.find(handler_id);
if (it != m_handlers_pending.end()) {
if (!it->value)
return false; // a deletion is pending
}
}
return m_handlers.contains(handler_id);
}
int m_signo;
void (*m_original_handler)(int); // TODO: can't use sighandler_t?
HashMap<int, Function<void(int)>> m_handlers;
HashMap<int, Function<void(int)>> m_handlers_pending;
bool m_calling_handlers { false };
};
friend class SignalHandlers;
Vector<QueuedEvent, 64> m_queued_events;
static HashMap<int, NonnullRefPtr<SignalHandlers>> s_signal_handlers;
static int s_next_signal_id;
static pid_t s_pid;
bool m_exit_requested { false };