nvidia app closing russian roulette

[tarek-y-ismail]

This seems to happen with multiple applications, but the most common crashes occur with firefox (unsnapped) and kgx.

With an external monitor hooked up to my nvidia GPU, there's a random chance that Mir will freeze (not crash) upon closing a window of one the aforementioned applications (among others, but those two are the two I most open and close windows with). @AlanGriffiths confirmed that this doesn't happen on his machine which doesn't use nvidia graphics.

I tried both inspecting a coredump and running mir under a debugger with and without cleanup signal handling code disabled. It appears that no signal is raised when the bug is triggered as gdb doesn't stop, I have to manually stop using ctrl + c. The stack trace doesn't contain any immediately suspicious functions. Logs also don't show any errors.

How I disabled signal handling / cleanup code

This is just an educated guess, so it might be wrong.

@@ -34,7 +34,6 @@
 
 namespace
 {
-constexpr std::array const fatal_error_signals = {SIGQUIT, SIGABRT, SIGFPE, SIGSEGV, SIGBUS };
 
 std::weak_ptr<mir::EmergencyCleanup> weak_emergency_cleanup;
 
@@ -210,17 +209,6 @@ void mir::run_mir(
           server_ptr->stop();
         };
 
-    struct sigaction old_action;
-    if ((sigaction(SIGHUP, nullptr, &old_action) == 0) && (old_action.sa_handler == SIG_IGN))
-    {
-        // If our parent process is ignoring SIGHUP (e.g. is nohup) then we do the same
-        main_loop->register_signal_handler({SIGINT, SIGTERM}, terminator);
-    }
-    else
-    {
-        main_loop->register_signal_handler({SIGINT, SIGHUP, SIGTERM}, terminator);
-    }
-
     FatalErrorStrategy fatal_error_strategy{config.the_fatal_error_strategy()};
 
     DisplayServer server(config);
@@ -228,53 +216,6 @@ void mir::run_mir(
 
     weak_emergency_cleanup = config.the_emergency_cleanup();
 
-    static std::atomic<unsigned int> concurrent_calls{0};
-
-    auto const raii = raii::paired_calls(
-        [&]()
-        {
-            if (!concurrent_calls++)
-            {
-                for (auto sig : fatal_error_signals)
-                {
-                    struct sigaction sig_handler_desc;
-                    sigfillset(&sig_handler_desc.sa_mask);
-                    sig_handler_desc.sa_flags = SA_SIGINFO;
-                    sig_handler_desc.sa_sigaction = &fatal_signal_cleanup;
-
-                    if (sigaction(sig, &sig_handler_desc, old_handlers.initialiser_for_signal(sig)))
-                    {
-                        using namespace std::string_literals;
-                        BOOST_THROW_EXCEPTION((
-                            std::system_error{
-                                errno,
-                                std::system_category(),
-                                "Failed to install signal handler for "s + signum_to_string(sig)
-                            }));
-                    }
-                }
-            }
-        },
-        [&]()
-        {
-            if (!--concurrent_calls)
-            {
-                for (auto sig : fatal_error_signals)
-                {
-                    if (sigaction(sig, old_handlers.at(sig), nullptr))
-                    {
-                        using namespace std::string_literals;
-                        BOOST_THROW_EXCEPTION((
-                            std::system_error{
-                                errno,
-                                std::system_category(),
-                                "Failed to install signal handler for "s + signum_to_string(sig)
-                            }));
-                    }
-                }
-            }
-        });
-
     mir::ThreadPoolExecutor::set_unhandled_exception_handler(&terminate_with_current_exception);
 
     init(server);