From 350ae90bb6e047cfd4bb011058bfc245826b156f Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Thu, 21 Aug 2025 02:56:17 +0300
Subject: [PATCH] Kernel: Make all futexes shared

Some stuff tries to use shared futexes so make them all shared. Private
futexes would be faster as they are process specific but supporting both
would need some reworks
---
 kernel/include/kernel/Process.h |  8 --------
 kernel/kernel/Process.cpp       | 34 ++++++++++++++++++---------------
 2 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 200a30ff..031e1620 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -350,14 +350,6 @@ namespace Kernel
 		BAN::UniqPtr<PageTable> m_page_table;
 		BAN::RefPtr<TTY> m_controlling_terminal;
 
-		struct futex_t
-		{
-			ThreadBlocker blocker;
-			uint32_t waiters { 0 };
-			uint32_t to_wakeup { 0 };
-		};
-		BAN::HashMap<paddr_t, BAN::UniqPtr<futex_t>> m_futexes;
-
 		friend class Thread;
 	};
 
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 3122d934..8ddfe24b 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -37,6 +37,15 @@ namespace Kernel
 	static BAN::Vector<Process*> s_processes;
 	static RecursiveSpinLock s_process_lock;
 
+	struct futex_t
+	{
+		ThreadBlocker blocker;
+		uint32_t waiters { 0 };
+		uint32_t to_wakeup { 0 };
+	};
+	static BAN::HashMap<paddr_t, BAN::UniqPtr<futex_t>> s_futexes;
+	static Mutex s_futex_lock;
+
 	static void for_each_process(const BAN::Function<BAN::Iteration(Process&)>& callback)
 	{
 		SpinLockGuard _(s_process_lock);
@@ -2720,17 +2729,12 @@ namespace Kernel
 		if (vaddr % 4)
 			return BAN::Error::from_errno(EINVAL);
 
-		const bool is_private  = (op & FUTEX_PRIVATE);
 		const bool is_realtime = (op & FUTEX_REALTIME);
 		op &= ~(FUTEX_PRIVATE | FUTEX_REALTIME);
 
-		if (!is_private)
-		{
-			dwarnln("TODO: shared futex");
-			return BAN::Error::from_errno(ENOTSUP);
-		}
+		// TODO: possibly optimize private futexes?
 
-		LockGuard _(m_process_lock);
+		LockGuard _(s_futex_lock);
 
 		auto* buffer_region = TRY(validate_and_pin_pointer_access(addr, sizeof(uint32_t), false));
 		BAN::ScopeGuard pin_guard([&] { if (buffer_region) buffer_region->unpin(); });
@@ -2761,20 +2765,20 @@ namespace Kernel
 						return SystemTimer::get().ns_since_boot() + (abs_ns - real_ns);
 					}());
 
-				auto it = m_futexes.find(paddr);
-				if (it == m_futexes.end())
-					it = TRY(m_futexes.emplace(paddr, TRY(BAN::UniqPtr<futex_t>::create())));
+				auto it = s_futexes.find(paddr);
+				if (it == s_futexes.end())
+					it = TRY(s_futexes.emplace(paddr, TRY(BAN::UniqPtr<futex_t>::create())));
 				futex_t* const futex = it->value.ptr();
 
 				futex->waiters++;
-				BAN::ScopeGuard _([futex, paddr, this] {
+				BAN::ScopeGuard _([futex, paddr] {
 					if (--futex->waiters == 0)
-						m_futexes.remove(paddr);
+						s_futexes.remove(paddr);
 				});
 
 				for (;;)
 				{
-					TRY(Thread::current().block_or_eintr_or_waketime_ns(futex->blocker, wake_time_ns, true, &m_process_lock));
+					TRY(Thread::current().block_or_eintr_or_waketime_ns(futex->blocker, wake_time_ns, true, &s_futex_lock));
 					if (BAN::atomic_load(*addr) == val || futex->to_wakeup == 0)
 						continue;
 					futex->to_wakeup--;
@@ -2783,8 +2787,8 @@ namespace Kernel
 			}
 			case FUTEX_WAKE:
 			{
-				auto it = m_futexes.find(paddr);
-				if (it == m_futexes.end())
+				auto it = s_futexes.find(paddr);
+				if (it == s_futexes.end())
 					return 0;
 				futex_t* const futex = it->value.ptr();