LibWebView: Force-exit unresponsive child processes

Let ProcessManager own hard process termination. Callers can now
schedule a forced exit after graceful shutdown is requested. The request
is canceled automatically when the process monitor observes exit.

Libraries/LibWebView/ProcessManager.cpp

@@ -10,6 +10,7 @@
 #include <LibCore/EventLoop.h>
 #include <LibCore/System.h>
 #include <LibWebView/ProcessManager.h>
+#include <signal.h>
 
 namespace WebView {
 
@@ -109,12 +110,48 @@ void ProcessManager::set_process_mach_port(pid_t pid, Core::MachPort&& port)
 Optional<Process> ProcessManager::remove_process(pid_t pid)
 {
     verify_event_loop();
+    cancel_forced_exit(pid);
     m_statistics.processes.remove_first_matching([&](auto const& info) {
         return (info->pid == pid);
     });
     return m_processes.take(pid);
 }
 
+void ProcessManager::cancel_forced_exit(pid_t pid)
+{
+    verify_event_loop();
+    if (auto timer = m_forced_exit_timers.take(pid); timer.has_value())
+        (*timer)->stop();
+}
+
+void ProcessManager::force_exit_after_timeout(pid_t pid, int timeout_ms)
+{
+    verify_event_loop();
+    if (!m_processes.contains(pid))
+        return;
+    if (m_forced_exit_timers.contains(pid))
+        return;
+
+    auto timer = Core::Timer::create_single_shot(timeout_ms, [this, pid] {
+        m_forced_exit_timers.remove(pid);
+        auto process = m_processes.get(pid);
+        if (!process.has_value())
+            return;
+
+#if defined(AK_OS_WINDOWS)
+        constexpr auto signal = SIGTERM;
+#else
+        constexpr auto signal = SIGKILL;
+#endif
+        dbgln("Force-killing unresponsive {} process {}", process_name_from_type(process->type()), pid);
+        auto result = Core::System::kill(pid, signal);
+        if (result.is_error())
+            dbgln("Failed to force-kill process {}: {}", pid, result.error());
+    });
+    timer->start();
+    m_forced_exit_timers.set(pid, move(timer));
+}
+
 void ProcessManager::update_all_process_statistics()
 {
     verify_event_loop();

Libraries/LibWebView/ProcessManager.h

@@ -7,10 +7,13 @@
 #pragma once
 
 #include <AK/Function.h>
+#include <AK/HashMap.h>
 #include <AK/JsonValue.h>
+#include <AK/RefPtr.h>
 #include <AK/Types.h>
 #include <LibCore/EventLoop.h>
 #include <LibCore/Platform/ProcessStatistics.h>
+#include <LibCore/Timer.h>
 #include <LibWebView/Forward.h>
 #include <LibWebView/Process.h>
 #include <LibWebView/ProcessMonitor.h>
@@ -31,6 +34,8 @@ public:
     void for_each_process(Function<void(Process&)>);
     Optional<Process> remove_process(pid_t);
     Optional<Process&> find_process(pid_t);
+    void cancel_forced_exit(pid_t);
+    void force_exit_after_timeout(pid_t, int timeout_ms);
 
 #if defined(AK_OS_MACH)
     void set_process_mach_port(pid_t, Core::MachPort&&);
@@ -47,6 +52,7 @@ private:
 
     Core::Platform::ProcessStatistics m_statistics;
     HashMap<pid_t, Process> m_processes;
+    HashMap<pid_t, RefPtr<Core::Timer>> m_forced_exit_timers;
     ProcessMonitor m_process_monitor;
     Core::EventLoop* m_creation_event_loop { &Core::EventLoop::current() };
 };