Kernel: Create RecursiveSpinLock and add it to Process

We now lock every function within Proccess, just to be sure.
Recursive lock allows us to use lock from the same thread even if
we already have the spinlock locked

kernel/kernel/Process.cpp

@@ -20,6 +20,8 @@ namespace Kernel
 
 	BAN::ErrorOr<void> Process::add_thread(entry_t entry, void* data)
 	{
+		LockGuard _(m_lock);
+		
 		auto thread = TRY(Thread::create(entry, data, this));
 		TRY(m_threads.push_back(thread));
 		if (auto res = Scheduler::get().add_thread(thread); res.is_error())
@@ -33,6 +35,7 @@ namespace Kernel
 
 	void Process::on_thread_exit(Thread& thread)
 	{
+		LockGuard _(m_lock);
 		(void)thread;
 	}
 
@@ -118,6 +121,8 @@ namespace Kernel
 
 	BAN::ErrorOr<BAN::String> Process::absolute_path_of(BAN::StringView path) const
 	{
+		LockGuard _(m_lock);
+
 		if (path.empty())
 			return m_working_directory;
 		BAN::String absolute_path;
@@ -142,6 +147,8 @@ namespace Kernel
 
 	BAN::ErrorOr<void> Process::validate_fd(int fd)
 	{
+		LockGuard _(m_lock);
+
 		if (fd < 0 || m_open_files.size() <= (size_t)fd || !m_open_files[fd].inode)
 			return BAN::Error::from_errno(EBADF);
 		return {};
@@ -149,12 +156,16 @@ namespace Kernel
 
 	Process::OpenFileDescription& Process::open_file_description(int fd)
 	{
+		LockGuard _(m_lock);
+
 		MUST(validate_fd(fd));
 		return m_open_files[fd];
 	}
 
 	BAN::ErrorOr<int> Process::get_free_fd()
 	{
+		LockGuard _(m_lock);
+
 		for (size_t fd = 0; fd < m_open_files.size(); fd++)
 			if (!m_open_files[fd].inode)
 				return fd;

kernel/kernel/SpinLock.cpp

@@ -1,4 +1,5 @@
 #include <kernel/SpinLock.h>
+#include <kernel/Thread.h>
 
 namespace Kernel
 {
@@ -21,4 +22,35 @@ namespace Kernel
 		return m_lock;
 	}
 
+	void RecursiveSpinLock::lock()
+	{
+		// FIXME: is this thread safe?
+		if (m_locker == Thread::current()->tid())
+		{
+			m_lock_depth++;
+		}
+		else
+		{
+			m_lock.lock();
+			ASSERT(m_locker == 0);
+			m_locker = Thread::current()->tid();
+			m_lock_depth = 1;
+		}
+	}
+
+	void RecursiveSpinLock::unlock()
+	{
+		m_lock_depth--;
+		if (m_lock_depth == 0)
+		{
+			m_locker = 0;
+			m_lock.unlock();
+		}
+	}
+
+	bool RecursiveSpinLock::is_locked() const
+	{
+		return m_lock.is_locked();
+	}
+
 }