From 814f0b215da912273f76750297c5ee93a9c00de6 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Fri, 24 Mar 2023 01:32:35 +0200
Subject: [PATCH] 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/include/kernel/Process.h  |  2 +-
 kernel/include/kernel/SpinLock.h | 19 +++++++++++++++++++
 kernel/kernel/Process.cpp        | 11 +++++++++++
 kernel/kernel/SpinLock.cpp       | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 0a74a380..b483023e 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -61,7 +61,7 @@ namespace Kernel
 
 		BAN::Vector<OpenFileDescription> m_open_files;
 
-		mutable SpinLock m_lock;
+		mutable RecursiveSpinLock m_lock;
 
 		pid_t m_pid = 0;
 		BAN::String m_working_directory;
diff --git a/kernel/include/kernel/SpinLock.h b/kernel/include/kernel/SpinLock.h
index ebf79df9..d3d2471a 100644
--- a/kernel/include/kernel/SpinLock.h
+++ b/kernel/include/kernel/SpinLock.h
@@ -2,6 +2,8 @@
 
 #include <BAN/NoCopyMove.h>
 
+#include <sys/types.h>
+
 namespace Kernel
 {
 
@@ -20,4 +22,21 @@ namespace Kernel
 		int m_lock = 0;
 	};
 
+	class RecursiveSpinLock
+	{
+		BAN_NON_COPYABLE(RecursiveSpinLock);
+		BAN_NON_MOVABLE(RecursiveSpinLock);
+
+	public:
+		RecursiveSpinLock() = default;
+		void lock();
+		void unlock();
+		bool is_locked() const;
+
+	private:
+		pid_t m_locker = 0;
+		uint32_t m_lock_depth = 0;
+		SpinLock m_lock;
+	};
+
 }
\ No newline at end of file
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 8b3e6fc7..4649aa44 100644
--- a/kernel/kernel/Process.cpp
+++ b/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;
diff --git a/kernel/kernel/SpinLock.cpp b/kernel/kernel/SpinLock.cpp
index 5f32ce2d..9ddffa98 100644
--- a/kernel/kernel/SpinLock.cpp
+++ b/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();
+	}
+
 }
\ No newline at end of file