Userland: Rename LibThread => LibThreading

Also rename the "LibThread" namespace to "Threading"

Userland/Libraries/LibThreading/BackgroundAction.cpp

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Queue.h>
+#include <LibThreading/BackgroundAction.h>
+#include <LibThreading/Lock.h>
+#include <LibThreading/Thread.h>
+
+static Threading::Lockable<Queue<Function<void()>>>* s_all_actions;
+static Threading::Thread* s_background_thread;
+
+static intptr_t background_thread_func()
+{
+    while (true) {
+        Function<void()> work_item;
+        {
+            Threading::Locker locker(s_all_actions->lock());
+
+            if (!s_all_actions->resource().is_empty())
+                work_item = s_all_actions->resource().dequeue();
+        }
+        if (work_item)
+            work_item();
+        else
+            sleep(1);
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
+static void init()
+{
+    s_all_actions = new Threading::Lockable<Queue<Function<void()>>>();
+    s_background_thread = &Threading::Thread::construct(background_thread_func).leak_ref();
+    s_background_thread->set_name("Background thread");
+    s_background_thread->start();
+}
+
+Threading::Lockable<Queue<Function<void()>>>& Threading::BackgroundActionBase::all_actions()
+{
+    if (s_all_actions == nullptr)
+        init();
+    return *s_all_actions;
+}
+
+Threading::Thread& Threading::BackgroundActionBase::background_thread()
+{
+    if (s_background_thread == nullptr)
+        init();
+    return *s_background_thread;
+}

Userland/Libraries/LibThreading/BackgroundAction.h

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/NonnullRefPtr.h>
+#include <AK/Optional.h>
+#include <AK/Queue.h>
+#include <LibCore/Event.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/Object.h>
+#include <LibThreading/Lock.h>
+#include <LibThreading/Thread.h>
+
+namespace Threading {
+
+template<typename Result>
+class BackgroundAction;
+
+class BackgroundActionBase {
+    template<typename Result>
+    friend class BackgroundAction;
+
+private:
+    BackgroundActionBase() { }
+
+    static Lockable<Queue<Function<void()>>>& all_actions();
+    static Thread& background_thread();
+};
+
+template<typename Result>
+class BackgroundAction final : public Core::Object
+    , private BackgroundActionBase {
+    C_OBJECT(BackgroundAction);
+
+public:
+    static NonnullRefPtr<BackgroundAction<Result>> create(
+        Function<Result()> action,
+        Function<void(Result)> on_complete = nullptr)
+    {
+        return adopt_ref(*new BackgroundAction(move(action), move(on_complete)));
+    }
+
+    virtual ~BackgroundAction() { }
+
+private:
+    BackgroundAction(Function<Result()> action, Function<void(Result)> on_complete)
+        : Core::Object(&background_thread())
+        , m_action(move(action))
+        , m_on_complete(move(on_complete))
+    {
+        Locker locker(all_actions().lock());
+
+        all_actions().resource().enqueue([this] {
+            m_result = m_action();
+            if (m_on_complete) {
+                Core::EventLoop::current().post_event(*this, make<Core::DeferredInvocationEvent>([this](auto&) {
+                    m_on_complete(m_result.release_value());
+                    this->remove_from_parent();
+                }));
+                Core::EventLoop::wake();
+            } else {
+                this->remove_from_parent();
+            }
+        });
+    }
+
+    Function<Result()> m_action;
+    Function<void(Result)> m_on_complete;
+    Optional<Result> m_result;
+};
+
+}

Userland/Libraries/LibThreading/CMakeLists.txt

@@ -0,0 +1,7 @@
+set(SOURCES
+    BackgroundAction.cpp
+    Thread.cpp
+)
+
+serenity_lib(LibThreading threading)
+target_link_libraries(LibThreading LibC LibCore LibPthread)

Userland/Libraries/LibThreading/Lock.h

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Assertions.h>
+#include <AK/Atomic.h>
+#include <AK/Types.h>
+
+#ifdef __serenity__
+#    include <unistd.h>
+#else
+#    include <pthread.h>
+#endif
+
+namespace Threading {
+
+class Lock {
+public:
+    Lock() { }
+    ~Lock() { }
+
+    void lock();
+    void unlock();
+
+private:
+#ifdef __serenity__
+    using ThreadID = int;
+
+    ALWAYS_INLINE static ThreadID self()
+    {
+        return gettid();
+    }
+#else
+    using ThreadID = pthread_t;
+
+    ALWAYS_INLINE static ThreadID self()
+    {
+        return pthread_self();
+    }
+#endif
+    Atomic<ThreadID> m_holder { 0 };
+    u32 m_level { 0 };
+};
+
+class Locker {
+public:
+    ALWAYS_INLINE explicit Locker(Lock& l)
+        : m_lock(l)
+    {
+        lock();
+    }
+    ALWAYS_INLINE ~Locker() { unlock(); }
+    ALWAYS_INLINE void unlock() { m_lock.unlock(); }
+    ALWAYS_INLINE void lock() { m_lock.lock(); }
+
+private:
+    Lock& m_lock;
+};
+
+ALWAYS_INLINE void Lock::lock()
+{
+    ThreadID tid = self();
+    if (m_holder == tid) {
+        ++m_level;
+        return;
+    }
+    for (;;) {
+        ThreadID expected = 0;
+        if (m_holder.compare_exchange_strong(expected, tid, AK::memory_order_acq_rel)) {
+            m_level = 1;
+            return;
+        }
+#ifdef __serenity__
+        donate(expected);
+#endif
+    }
+}
+
+inline void Lock::unlock()
+{
+    VERIFY(m_holder == self());
+    VERIFY(m_level);
+    if (m_level == 1)
+        m_holder.store(0, AK::memory_order_release);
+    else
+        --m_level;
+}
+
+template<typename T>
+class Lockable {
+public:
+    Lockable() { }
+
+    template<typename... Args>
+    Lockable(Args&&... args)
+        : m_resource(forward(args)...)
+    {
+    }
+
+    Lockable(T&& resource)
+        : m_resource(move(resource))
+    {
+    }
+    Lock& lock() { return m_lock; }
+    T& resource() { return m_resource; }
+
+    T lock_and_copy()
+    {
+        Locker locker(m_lock);
+        return m_resource;
+    }
+
+private:
+    T m_resource;
+    Lock m_lock;
+};
+
+}

Userland/Libraries/LibThreading/Thread.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibThreading/Thread.h>
+#include <pthread.h>
+#include <string.h>
+#include <unistd.h>
+
+Threading::Thread::Thread(Function<intptr_t()> action, StringView thread_name)
+    : Core::Object(nullptr)
+    , m_action(move(action))
+    , m_thread_name(thread_name.is_null() ? "" : thread_name)
+{
+    register_property("thread_name", [&] { return JsonValue { m_thread_name }; });
+    register_property("tid", [&] { return JsonValue { m_tid }; });
+}
+
+Threading::Thread::~Thread()
+{
+    if (m_tid) {
+        dbgln("Destroying thread \"{}\"({}) while it is still running!", m_thread_name, m_tid);
+        [[maybe_unused]] auto res = join();
+    }
+}
+
+void Threading::Thread::start()
+{
+    int rc = pthread_create(
+        &m_tid,
+        nullptr,
+        [](void* arg) -> void* {
+            Thread* self = static_cast<Thread*>(arg);
+            auto exit_code = self->m_action();
+            self->m_tid = 0;
+            return reinterpret_cast<void*>(exit_code);
+        },
+        static_cast<void*>(this));
+
+    VERIFY(rc == 0);
+    if (!m_thread_name.is_empty()) {
+        rc = pthread_setname_np(m_tid, m_thread_name.characters());
+        VERIFY(rc == 0);
+    }
+    dbgln("Started thread \"{}\", tid = {}", m_thread_name, m_tid);
+}

Userland/Libraries/LibThreading/Thread.h

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/DistinctNumeric.h>
+#include <AK/Function.h>
+#include <AK/Result.h>
+#include <AK/String.h>
+#include <LibCore/Object.h>
+#include <pthread.h>
+
+namespace Threading {
+
+TYPEDEF_DISTINCT_ORDERED_ID(intptr_t, ThreadError);
+
+class Thread final : public Core::Object {
+    C_OBJECT(Thread);
+
+public:
+    virtual ~Thread();
+
+    void start();
+
+    template<typename T = void>
+    Result<T, ThreadError> join();
+
+    String thread_name() const { return m_thread_name; }
+    pthread_t tid() const { return m_tid; }
+
+private:
+    explicit Thread(Function<intptr_t()> action, StringView thread_name = nullptr);
+    Function<intptr_t()> m_action;
+    pthread_t m_tid { 0 };
+    String m_thread_name;
+};
+
+template<typename T>
+Result<T, ThreadError> Thread::join()
+{
+    void* thread_return = nullptr;
+    int rc = pthread_join(m_tid, &thread_return);
+    if (rc != 0) {
+        return ThreadError { rc };
+    }
+
+    m_tid = 0;
+    if constexpr (IsVoid<T>)
+        return {};
+    else
+        return { static_cast<T>(thread_return) };
+}
+
+}