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Kernel: Fix heap expansions deadlock

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If a heap expansion is triggered by allocating from e.g. the
RangeAllocator, which may be holding a spin lock, we cannot
immediately allocate another block of backup memory, which could
require the same locks to be acquired. So, defer allocating the
backup memory

Fixes #4675
This commit is contained in:
Tom 2020-12-30 17:00:49 -07:00 committed by Andreas Kling
parent 4f1db41a6c
commit 22250780ff
Notes: sideshowbarker 2024-07-19 00:19:34 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/22250780ffa
Pull-request: https://github.com/SerenityOS/serenity/pull/4677
Issue: https://github.com/SerenityOS/serenity/issues/4675
Reviewed-by: https://github.com/awesomekling
1 changed files with 12 additions and 1 deletions
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13
Kernel/Heap/kmalloc.cpp
View file

@ -52,6 +52,8 @@
static RecursiveSpinLock s_lock; // needs to be recursive because of dump_backtrace()
static void kmalloc_allocate_backup_memory();
struct KmallocGlobalHeap {
struct ExpandGlobalHeap {
KmallocGlobalHeap& m_global_heap;
@ -94,7 +96,11 @@ struct KmallocGlobalHeap {
// backup heap before returning. Otherwise we potentially lose
// the ability to expand the heap next time we get called.
ScopeGuard guard([&]() {
m_global_heap.allocate_backup_memory();
// We may need to defer allocating backup memory because the
// heap expansion may have been triggered while holding some
// other spinlock. If the expansion happens to need the same
// spinlock we would deadlock. So, if we're in any lock, defer
Processor::current().deferred_call_queue(kmalloc_allocate_backup_memory);
});
// Now that we added our backup memory, check if the backup heap
@ -197,6 +203,11 @@ bool g_dump_kmalloc_stacks;
static u8* s_next_eternal_ptr;
static u8* s_end_of_eternal_range;
static void kmalloc_allocate_backup_memory()
{
g_kmalloc_global->allocate_backup_memory();
}
void kmalloc_enable_expand()
{
g_kmalloc_global->allocate_backup_memory();