luna: Use spinlocks in the heap implementation

kernel/CMakeLists.txt

@@ -18,7 +18,6 @@ set(SOURCES
     src/arch/Serial.cpp
     src/arch/Timer.cpp
     src/arch/PCI.cpp
-    src/thread/Spinlock.cpp
     src/thread/Thread.cpp
     src/thread/Scheduler.cpp
     src/sys/Syscall.cpp

kernel/src/Log.cpp

@@ -2,10 +2,10 @@
 #include "arch/CPU.h"
 #include "arch/Serial.h"
 #include "arch/Timer.h"
-#include "thread/Spinlock.h"
 #include "video/TextConsole.h"
 #include <luna/Format.h>
 #include <luna/SourceLocation.h>
+#include <luna/Spinlock.h>
 
 static bool g_debug_enabled = true;
 static bool g_serial_enabled = true;

kernel/src/memory/KernelVM.cpp

@@ -1,7 +1,7 @@
 #include "memory/KernelVM.h"
 #include "arch/MMU.h"
-#include "thread/Spinlock.h"
 #include <luna/Bitmap.h>
+#include <luna/Spinlock.h>
 
 static const u64 KERNEL_VM_RANGE_START = 0xffffffffc0000000;
 

kernel/src/memory/MemoryManager.cpp

@@ -2,10 +2,10 @@
 #include "arch/MMU.h"
 #include "memory/KernelVM.h"
 #include "memory/MemoryMap.h"
-#include "thread/Spinlock.h"
 #include <luna/Alignment.h>
 #include <luna/Bitmap.h>
 #include <luna/ScopeGuard.h>
+#include <luna/Spinlock.h>
 #include <luna/SystemError.h>
 #include <luna/Types.h>
 

luna/CMakeLists.txt

@@ -16,6 +16,8 @@ set(FREESTANDING_SOURCES
     src/TarStream.cpp
     src/DebugLog.cpp
     src/Heap.cpp
+    src/Spinlock.cpp
+    src/UBSAN.cpp
 )
 
 set(SOURCES

luna/include/luna/Option.h

@@ -138,26 +138,16 @@ template <typename T> class Option
   private:
     struct Storage
     {
-        u8 buffer[sizeof(T)];
-
-        T* fetch_ptr()
-        {
-            return (T*)buffer;
-        }
+        alignas(T) u8 buffer[sizeof(T)];
 
         T& fetch_reference()
         {
-            return *fetch_ptr();
-        }
-
-        const T* fetch_ptr() const
-        {
-            return (const T*)buffer;
+            return *__builtin_launder(reinterpret_cast<T*>(&buffer));
         }
 
         const T& fetch_reference() const
         {
-            return *fetch_ptr();
+            return *__builtin_launder(reinterpret_cast<const T*>(&buffer));
         }
 
         void store_reference(const T& ref)

luna/include/luna/Spinlock.h

@@ -1,6 +1,4 @@
 #pragma once
-#include "Log.h"
-#include "arch/CPU.h"
 #include <luna/Atomic.h>
 #include <luna/Option.h>
 
@@ -30,8 +28,15 @@ class ScopeLock
     ScopeLock(const ScopeLock&) = delete;
     ScopeLock(ScopeLock&&) = delete;
 
+    Spinlock& take_over()
+    {
+        m_taken_over = true;
+        return m_lock;
+    }
+
   private:
     Spinlock& m_lock;
+    bool m_taken_over { false };
 };
 
 class SafeScopeLock
@@ -107,25 +112,11 @@ template <typename T> class LockedValue
     {
     }
 
-#ifndef LOCKED_VALUE_DEBUG
     LockedValueGuard lock()
     {
         m_lock.lock();
         return { *this };
     }
-#else
-    LockedValueGuard lock()
-    {
-        if (m_lock.try_lock()) { return { *this }; }
-
-        kwarnln("Spinning on a locked LockedValue. This might lead to a deadlock...");
-
-        CPU::print_stack_trace();
-
-        m_lock.lock();
-        return { *this };
-    }
-#endif
 
     Option<LockedValueGuard> try_lock()
     {

luna/src/Heap.cpp

@@ -6,6 +6,7 @@
 #include <luna/LinkedList.h>
 #include <luna/SafeArithmetic.h>
 #include <luna/ScopeGuard.h>
+#include <luna/Spinlock.h>
 #include <luna/SystemError.h>
 
 #ifdef USE_FREESTANDING
@@ -45,9 +46,10 @@ static_assert(sizeof(HeapBlock) == 48UL);
 static const isize HEAP_BLOCK_SIZE = 48;
 
 static LinkedList<HeapBlock> heap;
+static Spinlock g_heap_lock;
 
-// If we're allocating a large amount of memory, map enough pages for it, but otherwise just use the default amount of
-// pages.
+// If we're allocating a large amount of memory, map enough pages for it, but otherwise just use the default amount
+// of pages.
 static usize get_pages_for_allocation(usize bytes)
 {
     usize pages = get_blocks_from_size(bytes, PAGE_SIZE);
@@ -178,6 +180,8 @@ Result<void*> malloc_impl(usize size, bool should_scrub)
 {
     if (!size) return (void*)BLOCK_MAGIC;
 
+    ScopeLock lock(g_heap_lock);
+
     size = align_up<16>(size);
 
     Option<HeapBlock*> block = heap.first();
@@ -231,6 +235,8 @@ Result<void> free_impl(void* ptr)
     if (ptr == (void*)BLOCK_MAGIC) return {}; // This pointer was returned from a call to malloc(0)
     if (!ptr) return {};
 
+    ScopeLock lock(g_heap_lock);
+
     HeapBlock* block = get_heap_block_for_pointer(ptr);
 
     if (block->magic != BLOCK_MAGIC)
@@ -286,6 +292,8 @@ Result<void*> realloc_impl(void* ptr, usize size)
         return (void*)BLOCK_MAGIC;
     }
 
+    ScopeLock lock(g_heap_lock);
+
     HeapBlock* const block = get_heap_block_for_pointer(ptr);
 
     if (block->magic != BLOCK_MAGIC)
@@ -327,6 +335,8 @@ Result<void*> realloc_impl(void* ptr, usize size)
 
     usize old_size = block->req_size;
 
+    lock.take_over().unlock();
+
     void* const new_ptr = TRY(malloc_impl(size, false));
     memcpy(new_ptr, ptr, old_size > size ? size : old_size);
     TRY(free_impl(ptr));

luna/src/Spinlock.cpp

@@ -1,6 +1,11 @@
-#include "thread/Spinlock.h"
-#include "Log.h"
-#include "arch/CPU.h"
+#include <luna/DebugLog.h>
+#include <luna/Spinlock.h>
+
+#ifdef ARCH_X86_64
+#define pause() asm volatile("pause")
+#else
+#error "Unsupported architecture"
+#endif
 
 void Spinlock::lock()
 {
@@ -8,7 +13,7 @@ void Spinlock::lock()
     while (!m_lock.compare_exchange_strong(expected, 1))
     {
         expected = 0;
-        CPU::pause();
+        pause();
     }
 }
 
@@ -23,7 +28,7 @@ void Spinlock::unlock()
     int expected = 1;
     if (!m_lock.compare_exchange_strong(expected, 0))
     {
-        kwarnln("Spinlock::unlock() called on an unlocked lock with value %d", expected);
+        dbgln("Spinlock::unlock() called on an unlocked lock with value %d", expected);
     }
 }
 
@@ -34,7 +39,7 @@ ScopeLock::ScopeLock(Spinlock& lock) : m_lock(lock)
 
 ScopeLock::~ScopeLock()
 {
-    m_lock.unlock();
+    if (!m_taken_over) m_lock.unlock();
 }
 
 const u32 RETRIES = 5000000;
@@ -42,7 +47,7 @@ const u32 RETRIES = 5000000;
 SafeScopeLock::SafeScopeLock(Spinlock& lock) : m_lock(lock)
 {
     u32 tries_left = RETRIES;
-    while (!lock.try_lock() && --tries_left) { CPU::pause(); }
+    while (!lock.try_lock() && --tries_left) { pause(); }
 
     if (tries_left) m_success = true;
 }