AK: Add Atomic.h

Use gcc built-in atomics

2 files changed, 16 insertions, 28 deletions

diff --git a/Kernel/Lock.cpp b/Kernel/Lock.cpp
index 7344685307..511d4b3e72 100644
--- a/Kernel/Lock.cpp
+++ b/Kernel/Lock.cpp
@@ -9,15 +9,15 @@ void Lock::lock()
         hang();
     }
     for (;;) {
-        if (CAS(&m_lock, 1, 0) == 0) {
+        bool expected = false;
+        if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
             if (!m_holder || m_holder == current) {
                 m_holder = current;
                 ++m_level;
-                memory_barrier();
-                m_lock = 0;
+                m_lock.store(false, AK::memory_order_release);
                 return;
             }
-            m_lock = 0;
+            m_lock.store(false, AK::memory_order_release);
         }
         Scheduler::donate_to(m_holder, m_name);
     }
@@ -26,18 +26,17 @@ void Lock::lock()
 void Lock::unlock()
 {
     for (;;) {
-        if (CAS(&m_lock, 1, 0) == 0) {
+        bool expected = false;
+        if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
             ASSERT(m_holder == current);
             ASSERT(m_level);
             --m_level;
             if (m_level) {
-                memory_barrier();
-                m_lock = 0;
+                m_lock.store(false, AK::memory_order_release);
                 return;
             }
             m_holder = nullptr;
-            memory_barrier();
-            m_lock = 0;
+            m_lock.store(false, AK::memory_order_release);
             return;
         }
         Scheduler::donate_to(m_holder, m_name);
@@ -47,25 +46,24 @@ void Lock::unlock()
 bool Lock::unlock_if_locked()
 {
     for (;;) {
-        if (CAS(&m_lock, 1, 0) == 0) {
+        bool expected = false;
+        if (m_lock.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
             if (m_level == 0) {
-                m_lock = 0;
+                m_lock.store(false, AK::memory_order_release);
                 return false;
             }
             if (m_holder != current) {
-                m_lock = 0;
+                m_lock.store(false, AK::memory_order_release);
                 return false;
             }
             ASSERT(m_level);
             --m_level;
             if (m_level) {
-                memory_barrier();
-                m_lock = 0;
+                m_lock.store(false, AK::memory_order_release);
                 return false;
             }
             m_holder = nullptr;
-            memory_barrier();
-            m_lock = 0;
+            m_lock.store(false, AK::memory_order_release);
             return true;
         }
     }
diff --git a/Kernel/Lock.h b/Kernel/Lock.h
index 755edf503e..77893f2819 100644
--- a/Kernel/Lock.h
+++ b/Kernel/Lock.h
@@ -2,6 +2,7 @@
 
 #include <AK/Assertions.h>
 #include <AK/Types.h>
+#include <AK/Atomic.h>
 #include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/KSyms.h>
 #include <Kernel/Scheduler.h>
@@ -9,17 +10,6 @@
 class Thread;
 extern Thread* current;
 
-static inline u32 CAS(volatile u32* mem, u32 newval, u32 oldval)
-{
-    u32 ret;
-    asm volatile(
-        "cmpxchgl %2, %1"
-        : "=a"(ret), "+m"(*mem)
-        : "r"(newval), "0"(oldval)
-        : "cc", "memory");
-    return ret;
-}
-
 class Lock {
 public:
     Lock(const char* name = nullptr)
@@ -35,7 +25,7 @@ public:
     const char* name() const { return m_name; }
 
 private:
-    volatile u32 m_lock { 0 };
+    Atomic<bool> m_lock { false };
     u32 m_level { 0 };
     Thread* m_holder { nullptr };
     const char* m_name { nullptr };