WindowServer: Sever the WSWindow/Process link when the process dies.

This fixes a deadlock where the WindowServer would get stuck trying to acquire a dead process's event stream lock.
luteresa · Feb 5, 2019 · 0c38a4c · 0c38a4c
1 parent ca16d9d
commit 0c38a4c
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Showing 4 changed files with 25 additions and 6 deletions.
diff --git a/Kernel/ProcessGUI.cpp b/Kernel/ProcessGUI.cpp
@@ -264,6 +264,7 @@ void Process::destroy_all_windows()
 {
  for (auto& it : m_windows) {
  auto message = make<WSMessage>(WSMessage::WM_DestroyWindow);
+ it.value->notify_process_died(Badge<Process>());
  WSMessageLoop::the().post_message(it.value.leak_ptr(), move(message), true);
  }
  m_windows.clear();

diff --git a/Kernel/Scheduler.cpp b/Kernel/Scheduler.cpp
@@ -236,7 +236,10 @@ bool Scheduler::context_switch(Process& process)
  current->set_state(Process::Runnable);
 
 #ifdef LOG_EVERY_CONTEXT_SWITCH
- dbgprintf("Scheduler: %s(%u) -> %s(%u)\n", current->name().characters(), current->pid(), process.name().characters(), process.pid());
+ dbgprintf("Scheduler: %s(%u) -> %s(%u) %w:%x\n",
+ current->name().characters(), current->pid(),
+ process.name().characters(), process.pid(),
+ process.tss().cs, process.tss().eip);
 #endif
  }
 

diff --git a/WindowServer/WSWindow.cpp b/WindowServer/WSWindow.cpp
@@ -5,7 +5,7 @@
 #include "Process.h"
 
 WSWindow::WSWindow(Process& process, int window_id)
- : m_process(process)
+ : m_process(&process)
  , m_window_id(window_id)
  , m_pid(process.pid())
 {
@@ -34,11 +34,13 @@ void WSWindow::set_rect(const Rect& rect)
  Rect old_rect;
  {
  WSWindowLocker locker(*this);
+ if (!m_process)
+ return;
  if (m_rect == rect)
  return;
  old_rect = m_rect;
  m_rect = rect;
- m_backing = GraphicsBitmap::create(m_process, m_rect.size());
+ m_backing = GraphicsBitmap::create(*m_process, m_rect.size());
  }
  WSWindowManager::the().notify_rect_changed(*this, old_rect, rect);
 }
@@ -124,11 +126,20 @@ void WSWindow::on_message(WSMessage& message)
  return;
 
  {
- LOCKER(m_process.gui_events_lock());
- m_process.gui_events().append(move(gui_event));
+ WSWindowLocker window_locker(*this);
+ if (!m_process)
+ return;
+ LOCKER(m_process->gui_events_lock());
+ m_process->gui_events().append(move(gui_event));
  }
 }
 
+void WSWindow::notify_process_died(Badge<Process>)
+{
+ WSWindowLocker locker(*this);
+ m_process = nullptr;
+}
+
 void WSWindow::set_global_cursor_tracking_enabled(bool enabled)
 {
  dbgprintf("WSWindow{%p} global_cursor_tracking <- %u\n", enabled);

diff --git a/WindowServer/WSWindow.h b/WindowServer/WSWindow.h
@@ -5,6 +5,8 @@
 #include <AK/AKString.h>
 #include <AK/InlineLinkedList.h>
 #include <AK/Lock.h>
+#include <AK/Badge.h>
+#include <Kernel/Process.h>
 #include "WSMessageReceiver.h"
 
 class Process;
@@ -45,6 +47,8 @@ class WSWindow final : public WSMessageReceiver, public InlineLinkedListNode<WSW
  void set_global_cursor_tracking_enabled(bool);
  bool global_cursor_tracking() const { return m_global_cursor_tracking_enabled; }
 
+ void notify_process_died(Badge<Process>);
+
  // For InlineLinkedList.
  // FIXME: Maybe make a ListHashSet and then WSWindowManager can just use that.
  WSWindow* m_next { nullptr };
@@ -58,7 +62,7 @@ class WSWindow final : public WSMessageReceiver, public InlineLinkedListNode<WSW
  bool m_global_cursor_tracking_enabled { false };
 
  RetainPtr<GraphicsBitmap> m_backing;
- Process& m_process;
+ Process* m_process { nullptr };
  int m_window_id { -1 };
  pid_t m_pid { -1 };
 };