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Kernel: Fix inconsistent lock acquisition order in kmalloc

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We always want to grab the page directory lock before the MM lock.
This fixes a deadlock I encountered when building DOOM with make -j4.
This commit is contained in:
Andreas Kling 2022-08-18 16:09:58 +02:00
parent 27c1135d30
commit abb84b9fcd
Notes: sideshowbarker 2024-07-17 20:33:50 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/abb84b9fcd
1 changed files with 2 additions and 2 deletions
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4
Kernel/Heap/kmalloc.cpp
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@ -332,8 +332,8 @@ struct KmallocGlobalData {
auto cpu_supports_nx = Processor::current().has_nx();
SpinlockLocker mm_locker(Memory::s_mm_lock);
SpinlockLocker pd_locker(MM.kernel_page_directory().get_lock());
SpinlockLocker mm_locker(Memory::s_mm_lock);
for (auto vaddr = new_subheap_base; !physical_pages.is_empty(); vaddr = vaddr.offset(PAGE_SIZE)) {
// FIXME: We currently leak physical memory when mapping it into the kmalloc heap.
@ -365,8 +365,8 @@ struct KmallocGlobalData {
// Make sure the entire kmalloc VM range is backed by page tables.
// This avoids having to deal with lazy page table allocation during heap expansion.
SpinlockLocker mm_locker(Memory::s_mm_lock);
SpinlockLocker pd_locker(MM.kernel_page_directory().get_lock());
SpinlockLocker mm_locker(Memory::s_mm_lock);
for (auto vaddr = reserved_region->range().base(); vaddr < reserved_region->range().end(); vaddr = vaddr.offset(PAGE_SIZE)) {
MM.ensure_pte(MM.kernel_page_directory(), vaddr);
}