Kernel: Port process thread lists to SpinLockProtectedValue

I had to move the thread list out of the protected base area of Process
so that it could live with its lock (which needs to be mutable).
Ideally it would live in the protected area, so maybe we can figure out
a way to do that later.

Kernel/Process.cpp

@@ -856,8 +856,9 @@ bool Process::remove_thread(Thread& thread)
     ProtectedDataMutationScope scope { *this };
     auto thread_cnt_before = m_thread_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
     VERIFY(thread_cnt_before != 0);
-    ScopedSpinLock thread_list_lock(m_thread_list_lock);
-    m_thread_list.remove(thread);
+    thread_list().with([&](auto& thread_list) {
+        thread_list.remove(thread);
+    });
     return thread_cnt_before == 1;
 }
 
@@ -865,8 +866,9 @@ bool Process::add_thread(Thread& thread)
 {
     ProtectedDataMutationScope scope { *this };
     bool is_first = m_thread_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed) == 0;
-    ScopedSpinLock thread_list_lock(m_thread_list_lock);
-    m_thread_list.append(thread);
+    thread_list().with([&](auto& thread_list) {
+        thread_list.append(thread);
+    });
     return is_first;
 }
 

Kernel/Process.h

@@ -102,7 +102,6 @@ protected:
     mode_t m_umask { 022 };
     VirtualAddress m_signal_trampoline;
     Atomic<u32> m_thread_count { 0 };
-    IntrusiveList<Thread, RawPtr<Thread>, &Thread::m_process_thread_list_node> m_thread_list;
     u8 m_termination_status { 0 };
     u8 m_termination_signal { 0 };
 };
@@ -724,9 +723,12 @@ public:
     const FileDescriptions& fds() const { return m_fds; }
 
 private:
-    FileDescriptions m_fds;
+    SpinLockProtectedValue<Thread::ListInProcess>& thread_list() { return m_thread_list; }
+    SpinLockProtectedValue<Thread::ListInProcess> const& thread_list() const { return m_thread_list; }
+
+    SpinLockProtectedValue<Thread::ListInProcess> m_thread_list;
 
-    mutable RecursiveSpinLock m_thread_list_lock;
+    FileDescriptions m_fds;
 
     const bool m_is_kernel_process;
     Atomic<State> m_state { State::Running };
@@ -818,25 +820,27 @@ inline void Process::for_each_child(Callback callback)
 template<IteratorFunction<Thread&> Callback>
 inline IterationDecision Process::for_each_thread(Callback callback) const
 {
-    ScopedSpinLock thread_list_lock(m_thread_list_lock);
-    for (auto& thread : m_thread_list) {
-        IterationDecision decision = callback(thread);
-        if (decision != IterationDecision::Continue)
-            return decision;
-    }
-    return IterationDecision::Continue;
+    return thread_list().with([&](auto& thread_list) -> IterationDecision {
+        for (auto& thread : thread_list) {
+            IterationDecision decision = callback(thread);
+            if (decision != IterationDecision::Continue)
+                return decision;
+        }
+        return IterationDecision::Continue;
+    });
 }
 
 template<IteratorFunction<Thread&> Callback>
 inline IterationDecision Process::for_each_thread(Callback callback)
 {
-    ScopedSpinLock thread_list_lock(m_thread_list_lock);
-    for (auto& thread : m_thread_list) {
-        IterationDecision decision = callback(thread);
-        if (decision != IterationDecision::Continue)
-            return decision;
-    }
-    return IterationDecision::Continue;
+    return thread_list().with([&](auto& thread_list) -> IterationDecision {
+        for (auto& thread : thread_list) {
+            IterationDecision decision = callback(thread);
+            if (decision != IterationDecision::Continue)
+                return decision;
+        }
+        return IterationDecision::Continue;
+    });
 }
 
 template<IteratorFunction<Process&> Callback>
@@ -875,18 +879,20 @@ inline void Process::for_each_child(Callback callback)
 template<VoidFunction<Thread&> Callback>
 inline IterationDecision Process::for_each_thread(Callback callback) const
 {
-    ScopedSpinLock thread_list_lock(m_thread_list_lock);
-    for (auto& thread : m_thread_list)
-        callback(thread);
+    thread_list().with([&](auto& thread_list) {
+        for (auto& thread : thread_list)
+            callback(thread);
+    });
     return IterationDecision::Continue;
 }
 
 template<VoidFunction<Thread&> Callback>
 inline IterationDecision Process::for_each_thread(Callback callback)
 {
-    ScopedSpinLock thread_list_lock(m_thread_list_lock);
-    for (auto& thread : m_thread_list)
-        callback(thread);
+    thread_list().with([&](auto& thread_list) {
+        for (auto& thread : thread_list)
+            callback(thread);
+    });
     return IterationDecision::Continue;
 }
 

Kernel/Thread.h

@@ -1372,6 +1372,9 @@ private:
     void yield_and_release_relock_big_lock();
     void yield_assuming_not_holding_big_lock();
     void drop_thread_count(bool);
+
+public:
+    using ListInProcess = IntrusiveList<Thread, RawPtr<Thread>, &Thread::m_process_thread_list_node>;
 };
 
 AK_ENUM_BITWISE_OPERATORS(Thread::FileBlocker::BlockFlags);