Kernel: Some small refinements to the thread blockers.

Committing some things my hands did while browsing through this code.

- Mark all leaf classes "final".
- FileDescriptionBlocker now stores a NonnullRefPtr<FileDescription>.
- FileDescriptionBlocker::blocked_description() now returns a reference.
- ConditionBlocker takes a Function&&.

Kernel/FileSystem/FileDescription.cpp

@@ -143,14 +143,16 @@ ssize_t FileDescription::write(const u8* data, ssize_t size)
     return nwritten;
 }
 
-bool FileDescription::can_write()
+bool FileDescription::can_write() const
 {
-    return m_file->can_write(*this);
+    // FIXME: Remove this const_cast.
+    return m_file->can_write(const_cast<FileDescription&>(*this));
 }
 
-bool FileDescription::can_read()
+bool FileDescription::can_read() const
 {
-    return m_file->can_read(*this);
+    // FIXME: Remove this const_cast.
+    return m_file->can_read(const_cast<FileDescription&>(*this));
 }
 
 ByteBuffer FileDescription::read_entire_file()

Kernel/FileSystem/FileDescription.h

@@ -36,8 +36,8 @@ public:
 
     KResult fchmod(mode_t);
 
-    bool can_read();
-    bool can_write();
+    bool can_read() const;
+    bool can_write() const;
 
     ssize_t get_dir_entries(u8* buffer, ssize_t);
 

Kernel/Scheduler.cpp

@@ -51,67 +51,63 @@ void Scheduler::beep()
     s_beep_timeout = g_uptime + 100;
 }
 
-Thread::FileDescriptionBlocker::FileDescriptionBlocker(const RefPtr<FileDescription>& description)
+Thread::FileDescriptionBlocker::FileDescriptionBlocker(const FileDescription& description)
     : m_blocked_description(description)
 {}
 
-RefPtr<FileDescription> Thread::FileDescriptionBlocker::blocked_description() const
+const FileDescription& Thread::FileDescriptionBlocker::blocked_description() const
 {
     return m_blocked_description;
 }
 
-Thread::AcceptBlocker::AcceptBlocker(const RefPtr<FileDescription>& description)
+Thread::AcceptBlocker::AcceptBlocker(const FileDescription& description)
     : FileDescriptionBlocker(description)
 {
 }
 
 bool Thread::AcceptBlocker::should_unblock(Thread&, time_t, long)
 {
-    auto& description = *blocked_description();
-    auto& socket = *description.socket();
-
+    auto& socket = *blocked_description().socket();
     return socket.can_accept();
 }
 
-Thread::ReceiveBlocker::ReceiveBlocker(const RefPtr<FileDescription>& description)
+Thread::ReceiveBlocker::ReceiveBlocker(const FileDescription& description)
     : FileDescriptionBlocker(description)
 {
 }
 
 bool Thread::ReceiveBlocker::should_unblock(Thread&, time_t now_sec, long now_usec)
 {
-    auto& description = *blocked_description();
-    auto& socket = *description.socket();
+    auto& socket = *blocked_description().socket();
     // FIXME: Block until the amount of data wanted is available.
     bool timed_out = now_sec > socket.receive_deadline().tv_sec || (now_sec == socket.receive_deadline().tv_sec && now_usec >= socket.receive_deadline().tv_usec);
-    if (timed_out || description.can_read())
+    if (timed_out || blocked_description().can_read())
         return true;
     return false;
 }
 
-Thread::ConnectBlocker::ConnectBlocker(const RefPtr<FileDescription>& description)
+Thread::ConnectBlocker::ConnectBlocker(const FileDescription& description)
     : FileDescriptionBlocker(description)
 {
 }
 
 bool Thread::ConnectBlocker::should_unblock(Thread&, time_t, long)
 {
-    auto& description = *blocked_description();
-    auto& socket = *description.socket();
+    auto& socket = *blocked_description().socket();
     return socket.is_connected();
 }
 
-Thread::WriteBlocker::WriteBlocker(const RefPtr<FileDescription>& description)
+Thread::WriteBlocker::WriteBlocker(const FileDescription& description)
     : FileDescriptionBlocker(description)
 {
 }
 
 bool Thread::WriteBlocker::should_unblock(Thread&, time_t, long)
 {
-    return blocked_description()->can_write();
+    return blocked_description().can_write();
 }
 
-Thread::ReadBlocker::ReadBlocker(const RefPtr<FileDescription>& description)
+Thread::ReadBlocker::ReadBlocker(const FileDescription& description)
     : FileDescriptionBlocker(description)
 {
 }
@@ -119,10 +115,10 @@ Thread::ReadBlocker::ReadBlocker(const RefPtr<FileDescription>& description)
 bool Thread::ReadBlocker::should_unblock(Thread&, time_t, long)
 {
     // FIXME: Block until the amount of data wanted is available.
-    return blocked_description()->can_read();
+    return blocked_description().can_read();
 }
 
-Thread::ConditionBlocker::ConditionBlocker(const char* state_string, Function<bool()> &condition)
+Thread::ConditionBlocker::ConditionBlocker(const char* state_string, Function<bool()>&& condition)
     : m_block_until_condition(move(condition))
     , m_state_string(state_string)
 {

Kernel/Thread.cpp

@@ -110,7 +110,7 @@ void Thread::unblock()
 
 void Thread::block_until(const char* state_string, Function<bool()>&& condition)
 {
-    block<ConditionBlocker>(state_string, condition);
+    block<ConditionBlocker>(state_string, move(condition));
 }
 
 void Thread::block_helper()

Kernel/Thread.h

@@ -75,62 +75,62 @@ public:
 
     class FileDescriptionBlocker : public Blocker {
     public:
-        FileDescriptionBlocker(const RefPtr<FileDescription>& description);
-        RefPtr<FileDescription> blocked_description() const;
+        explicit FileDescriptionBlocker(const FileDescription&);
+        const FileDescription& blocked_description() const;
 
     private:
-        RefPtr<FileDescription> m_blocked_description;
+        NonnullRefPtr<FileDescription> m_blocked_description;
     };
 
-    class AcceptBlocker : public FileDescriptionBlocker {
+    class AcceptBlocker final : public FileDescriptionBlocker {
     public:
-        AcceptBlocker(const RefPtr<FileDescription>& description);
+        explicit AcceptBlocker(const FileDescription&);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return "Accepting"; }
     };
 
-    class ReceiveBlocker : public FileDescriptionBlocker {
+    class ReceiveBlocker final : public FileDescriptionBlocker {
     public:
-        ReceiveBlocker(const RefPtr<FileDescription>& description);
+        explicit ReceiveBlocker(const FileDescription&);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return "Receiving"; }
     };
 
-    class ConnectBlocker : public FileDescriptionBlocker {
+    class ConnectBlocker final : public FileDescriptionBlocker {
     public:
-        ConnectBlocker(const RefPtr<FileDescription>& description);
+        explicit ConnectBlocker(const FileDescription&);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return "Connecting"; }
     };
 
-    class WriteBlocker : public FileDescriptionBlocker {
+    class WriteBlocker final : public FileDescriptionBlocker {
     public:
-        WriteBlocker(const RefPtr<FileDescription>& description);
+        explicit WriteBlocker(const FileDescription&);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return "Writing"; }
     };
 
-    class ReadBlocker : public FileDescriptionBlocker {
+    class ReadBlocker final : public FileDescriptionBlocker {
     public:
-        ReadBlocker(const RefPtr<FileDescription>& description);
+        explicit ReadBlocker(const FileDescription&);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return "Reading"; }
     };
 
-    class ConditionBlocker : public Blocker {
+    class ConditionBlocker final : public Blocker {
     public:
-        ConditionBlocker(const char* state_string, Function<bool()> &condition);
+        ConditionBlocker(const char* state_string, Function<bool()>&& condition);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return m_state_string; }
 
     private:
         Function<bool()> m_block_until_condition;
-        const char* m_state_string;
+        const char* m_state_string { nullptr };
     };
 
-    class SleepBlocker : public Blocker {
+    class SleepBlocker final : public Blocker {
     public:
-        SleepBlocker(u64 wakeup_time);
+        explicit SleepBlocker(u64 wakeup_time);
         virtual bool should_unblock(Thread&, time_t, long) override;
         virtual const char* state_string() const override { return "Sleeping"; }
 
@@ -138,7 +138,7 @@ public:
         u64 m_wakeup_time { 0 };
     };
 
-    class SelectBlocker : public Blocker {
+    class SelectBlocker final : public Blocker {
     public:
         typedef Vector<int, FD_SETSIZE> FDVector;
         SelectBlocker(const timeval& tv, bool select_has_timeout, const FDVector& read_fds, const FDVector& write_fds, const FDVector& except_fds);
@@ -153,7 +153,7 @@ public:
         const FDVector& m_select_exceptional_fds;
     };
 
-    class WaitBlocker : public Blocker {
+    class WaitBlocker final : public Blocker {
     public:
         WaitBlocker(int wait_options, pid_t& waitee_pid);
         virtual bool should_unblock(Thread&, time_t, long) override;
@@ -164,7 +164,7 @@ public:
         pid_t& m_waitee_pid;
     };
 
-    class SemiPermanentBlocker : public Blocker {
+    class SemiPermanentBlocker final : public Blocker {
     public:
         enum class Reason {
             Lurking,
@@ -192,10 +192,7 @@ public:
     u32 times_scheduled() const { return m_times_scheduled; }
 
     bool is_stopped() const { return m_state == Stopped; }
-    bool is_blocked() const
-    {
-        return m_state == Blocked;
-    }
+    bool is_blocked() const { return m_state == Blocked; }
     bool in_kernel() const { return (m_tss.cs & 0x03) == 0; }
 
     u32 frame_ptr() const { return m_tss.ebp; }