From 3ac977f50bfd8dc9be2fe6e92211c67d7958a5ef Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Sat, 12 Jan 2019 23:23:35 +0100
Subject: [PATCH] Paper over a race in DoubleBuffer.

I'm still somewhat okay throwing InterruptDisabler at races as they screw me.
Eventually I'm gonna have to devise a different strategy though.
---
 Kernel/DoubleBuffer.cpp |  6 +++++-
 Kernel/kmalloc.cpp      |  2 +-
 Kernel/kmalloc.h        | 10 +++++++++-
 Widgets/EventLoop.cpp   |  6 +++++-
 4 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/Kernel/DoubleBuffer.cpp b/Kernel/DoubleBuffer.cpp
index 30c125bd22975b..ab85c1b6ab3e3d 100644
--- a/Kernel/DoubleBuffer.cpp
+++ b/Kernel/DoubleBuffer.cpp
@@ -2,9 +2,13 @@
 
 void DoubleBuffer::flip()
 {
+    InterruptDisabler disabler;
     ASSERT(m_read_buffer_index == m_read_buffer->size());
     swap(m_read_buffer, m_write_buffer);
-    m_write_buffer->clear();
+    if (m_write_buffer->capacity() < 32)
+        m_write_buffer->clear_with_capacity();
+    else
+        m_write_buffer->clear();
     m_read_buffer_index = 0;
 }
 
diff --git a/Kernel/kmalloc.cpp b/Kernel/kmalloc.cpp
index fd837e03d0a278..d297d28e2d67d7 100644
--- a/Kernel/kmalloc.cpp
+++ b/Kernel/kmalloc.cpp
@@ -90,7 +90,7 @@ void* kmalloc_page_aligned(size_t size)
     return ptr;
 }
 
-void* kmalloc(dword size)
+void* kmalloc_impl(dword size)
 {
     InterruptDisabler disabler;
 
diff --git a/Kernel/kmalloc.h b/Kernel/kmalloc.h
index afbaa2e5a1da0a..1aeae01099f6bd 100644
--- a/Kernel/kmalloc.h
+++ b/Kernel/kmalloc.h
@@ -1,7 +1,7 @@
 #pragma once
 
 void kmalloc_init();
-void *kmalloc(dword size) __attribute__ ((malloc));
+void* kmalloc_impl(dword size) __attribute__ ((malloc));
 void* kmalloc_eternal(size_t) __attribute__ ((malloc));
 void* kmalloc_page_aligned(size_t) __attribute__ ((malloc));
 void* kmalloc_aligned(size_t, size_t alignment) __attribute__ ((malloc));
@@ -17,3 +17,11 @@ extern volatile size_t kmalloc_sum_page_aligned;
 
 inline void* operator new(size_t, void* p) { return p; }
 inline void* operator new[](size_t, void* p) { return p; }
+
+ALWAYS_INLINE void* kmalloc(size_t size)
+{
+    // Any kernel allocation >= 32K is very suspicious, catch them.
+    if (size >= 0x8000)
+        asm volatile("cli;hlt");
+    return kmalloc_impl(size);
+}
diff --git a/Widgets/EventLoop.cpp b/Widgets/EventLoop.cpp
index d4c026cebc21b0..22b94cdd03e3ba 100644
--- a/Widgets/EventLoop.cpp
+++ b/Widgets/EventLoop.cpp
@@ -36,7 +36,11 @@ int EventLoop::exec()
     for (;;) {
         if (m_queuedEvents.is_empty())
             waitForEvent();
-        auto events = move(m_queuedEvents);
+        Vector<QueuedEvent> events;
+        {
+            InterruptDisabler disabler;
+            events = move(m_queuedEvents);
+        }
         for (auto& queuedEvent : events) {
             auto* receiver = queuedEvent.receiver;
             auto& event = *queuedEvent.event;