Rework WindowServer to use select() in its main event loop.

The system can finally idle without burning CPU. :^)

There are some issues with scheduling making the mouse cursor sloppy
and unresponsive that need to be dealt with.

Kernel/Keyboard.cpp

@@ -125,7 +125,12 @@ ssize_t Keyboard::read(Process&, byte* buffer, size_t size)
     while ((size_t)nread < size) {
         if (m_queue.is_empty())
             break;
-        buffer[nread++] = m_queue.dequeue().character;
+        // Don't return partial data frames.
+        if ((size - nread) < 2)
+            break;
+        auto key = m_queue.dequeue();
+        buffer[nread++] = key.character;
+        buffer[nread++] = key.modifiers;
     }
     return nread;
 }

Kernel/Keyboard.h

@@ -32,16 +32,16 @@ public:
 
     void set_client(KeyboardClient* client) { m_client = client; }
 
+    // ^CharacterDevice
+    virtual ssize_t read(Process&, byte* buffer, size_t) override;
+    virtual bool can_read(Process&) const override;
+    virtual ssize_t write(Process&, const byte* buffer, size_t) override;
+    virtual bool can_write(Process&) const override { return true; }
+
 private:
     // ^IRQHandler
     virtual void handle_irq() override;
 
-    // ^CharacterDevice
-    virtual ssize_t read(Process&, byte* buffer, size_t) override;
-    virtual ssize_t write(Process&, const byte* buffer, size_t) override;
-    virtual bool can_read(Process&) const override;
-    virtual bool can_write(Process&) const override { return true; }
-
     void emit(byte);
 
     KeyboardClient* m_client { nullptr };

Kernel/MemoryManager.cpp

@@ -537,7 +537,7 @@ bool MemoryManager::validate_user_read(const Process& process, LinearAddress lad
     auto pte = PageTableEntry(&pde.pageTableBase()[pageTableIndex]);
     if (!pte.is_present())
         return false;
-    if (!pte.is_user_allowed())
+    if (process.isRing3() && !pte.is_user_allowed())
         return false;
     return true;
 }
@@ -552,7 +552,7 @@ bool MemoryManager::validate_user_write(const Process& process, LinearAddress la
     auto pte = PageTableEntry(&pde.pageTableBase()[pageTableIndex]);
     if (!pte.is_present())
         return false;
-    if (!pte.is_user_allowed())
+    if (process.isRing3() && !pte.is_user_allowed())
         return false;
     if (!pte.is_writable())
         return false;

Kernel/PS2MouseDevice.cpp

@@ -129,6 +129,7 @@ ssize_t PS2MouseDevice::read(Process&, byte* buffer, size_t size)
     while ((size_t)nread < size) {
         if (m_queue.is_empty())
             break;
+        // FIXME: Don't return partial data frames.
         buffer[nread++] = m_queue.dequeue();
     }
     return nread;

Kernel/Process.cpp

@@ -1295,6 +1295,7 @@ int Process::sys$open(const char* path, int options)
     if (number_of_open_file_descriptors() >= m_max_open_file_descriptors)
         return -EMFILE;
     int error = -EWHYTHO;
+    ASSERT(cwd_inode());
     auto descriptor = VFS::the().open(path, error, options, cwd_inode()->identifier());
     if (!descriptor)
         return error;
@@ -1960,8 +1961,15 @@ int Process::sys$select(const Syscall::SC_select_params* params)
     transfer_fds(writefds, m_select_write_fds);
     transfer_fds(readfds, m_select_read_fds);
 
-    block(BlockedSelect);
-    Scheduler::yield();
+#ifdef DEBUG_IO
+    dbgprintf("%s<%u> selecting on (read:%u, write:%u)\n", name().characters(), pid(), m_select_read_fds.size(), m_select_write_fds.size());
+#endif
+
+    if (!m_wakeup_requested) {
+        block(BlockedSelect);
+        Scheduler::yield();
+    }
+    m_wakeup_requested = false;
 
     int markedfds = 0;
 
@@ -1989,3 +1997,11 @@ int Process::sys$select(const Syscall::SC_select_params* params)
 
     return markedfds;
 }
+
+Inode* Process::cwd_inode()
+{
+    // FIXME: This is retarded factoring.
+    if (!m_cwd)
+        m_cwd = VFS::the().root_inode();
+    return m_cwd.ptr();
+}

Kernel/Process.h

@@ -236,7 +236,7 @@ public:
     template<typename T> bool validate_read_typed(T* value, size_t count = 1) { return validate_read(value, sizeof(T) * count); }
     template<typename T> bool validate_write_typed(T* value, size_t count = 1) { return validate_write(value, sizeof(T) * count); }
 
-    Inode* cwd_inode() { return m_cwd.ptr(); }
+    Inode* cwd_inode();
     Inode* executable_inode() { return m_executable.ptr(); }
 
     size_t number_of_open_file_descriptors() const;
@@ -256,6 +256,9 @@ public:
     Vector<GUI_Event>& gui_events() { return m_gui_events; }
     SpinLock& gui_events_lock() { return m_gui_events_lock; }
 
+    bool wakeup_requested() { return m_wakeup_requested; }
+    void request_wakeup() { m_wakeup_requested = true; }
+
 private:
     friend class MemoryManager;
     friend class Scheduler;
@@ -357,6 +360,8 @@ private:
     Vector<GUI_Event> m_gui_events;
     SpinLock m_gui_events_lock;
     int m_next_window_id { 1 };
+
+    dword m_wakeup_requested { false };
 };
 
 extern Process* current;

Kernel/ProcessGUI.cpp

@@ -108,8 +108,7 @@ int Process::gui$invalidate_window(int window_id)
     if (it == m_windows.end())
         return -EBADWINDOW;
     auto& window = *(*it).value;
-    // FIXME: This should queue up a message that the window server process can read.
-    //        Poking into its data structures is not good.
     WSEventLoop::the().post_event(&window, make<WSEvent>(WSEvent::WM_Invalidate));
+    WSEventLoop::the().server_process().request_wakeup();
     return 0;
 }

Kernel/Scheduler.cpp

@@ -65,6 +65,11 @@ bool Scheduler::pick_next()
         }
 
         if (process.state() == Process::BlockedSelect) {
+            if (process.wakeup_requested()) {
+                process.m_wakeup_requested = false;
+                process.unblock();
+                return true;
+            }
             for (int fd : process.m_select_read_fds) {
                 if (process.m_fds[fd].descriptor->can_read(process)) {
                     process.unblock();

Kernel/init.cpp

@@ -37,6 +37,7 @@ VirtualConsole* tty3;
 Keyboard* keyboard;
 PS2MouseDevice* ps2mouse;
 GUIEventDevice* gui_event_device;
+VFS* vfs;
 
 #ifdef STRESS_TEST_SPAWNING
 static void spawn_stress() NORETURN;
@@ -62,8 +63,6 @@ static void init_stage2()
 {
     Syscall::initialize();
 
-    auto vfs = make<VFS>();
-
     auto dev_zero = make<ZeroDevice>();
     vfs->register_character_device(*dev_zero);
 
@@ -138,6 +137,9 @@ void init()
     gdt_init();
     idt_init();
 
+    VFS::initialize_globals();
+    vfs = new VFS;
+
     keyboard = new Keyboard;
     ps2mouse = new PS2MouseDevice;
     gui_event_device = new GUIEventDevice;
@@ -153,7 +155,6 @@ void init()
 
     MemoryManager::initialize();
 
-    VFS::initialize_globals();
     StringImpl::initialize_globals();
 
     PIT::initialize();

Kernel/sync.sh

@@ -8,6 +8,7 @@ mknod mnt/dev/tty0 c 4 0
 mknod mnt/dev/tty1 c 4 1
 mknod mnt/dev/tty2 c 4 2
 mknod mnt/dev/tty3 c 4 3
+mknod mnt/dev/keyboard c 85 1
 mknod mnt/dev/psaux c 10 1
 mknod mnt/dev/ptmx c 5 2
 mknod mnt/dev/ptm0 c 10 0