Kernel: Reduce LOCK_DEBUG ifdefs by utilizing Kernel::LockLocation

The LOCK_DEBUG conditional code is pretty ugly for a feature that we
only use rarely. We can remove a significant amount of this code by
utilizing a zero sized fake type when not building in LOCK_DEBUG mode.

This lets us keep the same API, but just let the compiler optimize it
away when don't actually care about the location the caller came from.

Kernel/Locking/Mutex.cpp

@@ -4,22 +4,16 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#ifdef LOCK_DEBUG
-#    include <AK/SourceLocation.h>
-#endif
 #include <Kernel/Debug.h>
 #include <Kernel/KSyms.h>
+#include <Kernel/Locking/LockLocation.h>
 #include <Kernel/Locking/Mutex.h>
 #include <Kernel/Locking/SpinLock.h>
 #include <Kernel/Thread.h>
 
 namespace Kernel {
 
-#if LOCK_DEBUG
-void Mutex::lock(Mode mode, const SourceLocation& location)
-#else
-void Mutex::lock(Mode mode)
-#endif
+void Mutex::lock(Mode mode, [[maybe_unused]] const LockLocation& location)
 {
     // NOTE: This may be called from an interrupt handler (not an IRQ handler)
     // and also from within critical sections!
@@ -318,11 +312,7 @@ auto Mutex::force_unlock_if_locked(u32& lock_count_to_restore) -> Mode
     return current_mode;
 }
 
-#if LOCK_DEBUG
-void Mutex::restore_lock(Mode mode, u32 lock_count, const SourceLocation& location)
-#else
-void Mutex::restore_lock(Mode mode, u32 lock_count)
-#endif
+void Mutex::restore_lock(Mode mode, u32 lock_count, [[maybe_unused]] const LockLocation& location)
 {
     VERIFY(mode != Mode::Unlocked);
     VERIFY(lock_count > 0);

Kernel/Locking/Mutex.h

@@ -11,6 +11,7 @@
 #include <AK/HashMap.h>
 #include <AK/Types.h>
 #include <Kernel/Forward.h>
+#include <Kernel/Locking/LockLocation.h>
 #include <Kernel/Locking/LockMode.h>
 #include <Kernel/WaitQueue.h>
 
@@ -31,13 +32,8 @@ public:
     }
     ~Mutex() = default;
 
-#if LOCK_DEBUG
-    void lock(Mode mode = Mode::Exclusive, const SourceLocation& location = SourceLocation::current());
-    void restore_lock(Mode, u32, const SourceLocation& location = SourceLocation::current());
-#else
-    void lock(Mode = Mode::Exclusive);
-    void restore_lock(Mode, u32);
-#endif
+    void lock(Mode mode = Mode::Exclusive, const LockLocation& location = LockLocation::current());
+    void restore_lock(Mode, u32, const LockLocation& location = LockLocation::current());
 
     void unlock();
     [[nodiscard]] Mode force_unlock_if_locked(u32&);
@@ -115,18 +111,10 @@ public:
     {
     }
 
-#if LOCK_DEBUG
-    ALWAYS_INLINE explicit MutexLocker(Mutex& l, Mutex::Mode mode = Mutex::Mode::Exclusive, const SourceLocation& location = SourceLocation::current())
-#else
-    ALWAYS_INLINE explicit MutexLocker(Mutex& l, Mutex::Mode mode = Mutex::Mode::Exclusive)
-#endif
+    ALWAYS_INLINE explicit MutexLocker(Mutex& l, Mutex::Mode mode = Mutex::Mode::Exclusive, const LockLocation& location = LockLocation::current())
         : m_lock(&l)
     {
-#if LOCK_DEBUG
         m_lock->lock(mode, location);
-#else
-        m_lock->lock(mode);
-#endif
     }
 
     ALWAYS_INLINE ~MutexLocker()
@@ -143,38 +131,22 @@ public:
         m_lock->unlock();
     }
 
-#if LOCK_DEBUG
-    ALWAYS_INLINE void attach_and_lock(Mutex& lock, Mutex::Mode mode = Mutex::Mode::Exclusive, const SourceLocation& location = SourceLocation::current())
-#else
-    ALWAYS_INLINE void attach_and_lock(Mutex& lock, Mutex::Mode mode = Mutex::Mode::Exclusive)
-#endif
+    ALWAYS_INLINE void attach_and_lock(Mutex& lock, Mutex::Mode mode = Mutex::Mode::Exclusive, const LockLocation& location = LockLocation::current())
     {
         VERIFY(!m_locked);
         m_lock = &lock;
         m_locked = true;
 
-#if LOCK_DEBUG
         m_lock->lock(mode, location);
-#else
-        m_lock->lock(mode);
-#endif
     }
 
-#if LOCK_DEBUG
-    ALWAYS_INLINE void lock(Mutex::Mode mode = Mutex::Mode::Exclusive, const SourceLocation& location = SourceLocation::current())
-#else
-    ALWAYS_INLINE void lock(Mutex::Mode mode = Mutex::Mode::Exclusive)
-#endif
+    ALWAYS_INLINE void lock(Mutex::Mode mode = Mutex::Mode::Exclusive, const LockLocation& location = LockLocation::current())
     {
         VERIFY(m_lock);
         VERIFY(!m_locked);
         m_locked = true;
 
-#if LOCK_DEBUG
         m_lock->lock(mode, location);
-#else
-        m_lock->lock(mode);
-#endif
     }
 
 private:

Kernel/Thread.cpp

@@ -514,7 +514,7 @@ void Thread::finalize()
         dbgln("Thread {} leaking {} Locks!", *this, lock_count());
         ScopedSpinLock list_lock(m_holding_locks_lock);
         for (auto& info : m_holding_locks_list) {
-            const auto& location = info.source_location;
+            const auto& location = info.lock_location;
             dbgln(" - Mutex: \"{}\" @ {} locked in function \"{}\" at \"{}:{}\" with a count of: {}", info.lock->name(), info.lock, location.function_name(), location.filename(), location.line_number(), info.count);
         }
         VERIFY_NOT_REACHED();

Kernel/Thread.h

@@ -12,9 +12,6 @@
 #include <AK/IntrusiveList.h>
 #include <AK/Optional.h>
 #include <AK/OwnPtr.h>
-#ifdef LOCK_DEBUG
-#    include <AK/SourceLocation.h>
-#endif
 #include <AK/String.h>
 #include <AK/Time.h>
 #include <AK/Vector.h>
@@ -27,6 +24,7 @@
 #include <Kernel/Forward.h>
 #include <Kernel/KResult.h>
 #include <Kernel/KString.h>
+#include <Kernel/Locking/LockLocation.h>
 #include <Kernel/Locking/LockMode.h>
 #include <Kernel/Memory/VirtualRange.h>
 #include <Kernel/Scheduler.h>
@@ -1152,7 +1150,7 @@ public:
     RecursiveSpinLock& get_lock() const { return m_lock; }
 
 #if LOCK_DEBUG
-    void holding_lock(Mutex& lock, int refs_delta, const SourceLocation& location)
+    void holding_lock(Mutex& lock, int refs_delta, const LockLocation& location)
     {
         VERIFY(refs_delta != 0);
         m_holding_locks.fetch_add(refs_delta, AK::MemoryOrder::memory_order_relaxed);
@@ -1317,7 +1315,7 @@ private:
 #if LOCK_DEBUG
     struct HoldingLockInfo {
         Mutex* lock;
-        SourceLocation source_location;
+        LockLocation lock_location;
         unsigned count;
     };
     Atomic<u32> m_holding_locks { 0 };