mirrors/ladybird
1
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2025-01-24 10:12:25 -05:00
Code Issues Projects Releases Packages Wiki Activity

Kernel: Prevent recursive expansion or removing memory while expanding it

Browse source 
The process of expanding memory requires allocations and deallocations
on the heap itself. So, while we're trying to expand the heap, don't
remove memory just because we might briefly not need it. Also prevent
recursive expansion attempts.
This commit is contained in:
Tom 2020-09-01 16:02:39 -06:00 • committed by Andreas Kling
parent dec3998b3c
commit ee51b28edd
Notes: sideshowbarker 2024-07-19 02:55:45 +09:00
1 changed files with 16 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
Kernel/Heap/Heap.h
View file

@ -28,6 +28,7 @@
#include <AK/Bitmap.h>
#include <AK/ScopeGuard.h>
#include <AK/TemporaryChange.h>
#include <AK/Vector.h>
#include <AK/kmalloc.h>
@ -242,6 +243,18 @@ public:
return sizeof(SubHeap) + HeapType::calculate_memory_for_bytes(bytes);
}
bool expand_memory(size_t size)
{
if (m_expanding)
return false;
// Allocating more memory itself may trigger allocations and deallocations
// on this heap. We need to prevent recursive expansion. We also disable
// removing memory while trying to expand the heap.
TemporaryChange change(m_expanding, true);
return ExpandableHeapTraits<ExpandHeap>::add_memory(m_expand, size);
}
void* allocate(size_t size)
{
do {
@ -256,7 +269,7 @@ public:
// This is especially true for the kmalloc heap, where adding memory
// requires several other objects to be allocated just to be able to
// expand the heap.
} while (ExpandableHeapTraits<ExpandHeap>::add_memory(m_expand, size));
} while (expand_memory(size));
return nullptr;
}
@ -267,7 +280,7 @@ public:
for (auto* subheap = &m_heaps; subheap; subheap = subheap->next) {
if (subheap->heap.contains(ptr)) {
subheap->heap.deallocate(ptr);
if (subheap->heap.allocated_chunks() == 0 && subheap != &m_heaps) {
if (subheap->heap.allocated_chunks() == 0 && subheap != &m_heaps && !m_expanding) {
// Since remove_memory may free subheap, we need to save the
// next pointer before calling it
auto* next_subheap = subheap->next;
@ -358,6 +371,7 @@ public:
private:
SubHeap m_heaps;
ExpandHeap m_expand;
bool m_expanding { false };
};
}