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https://github.com/RGBCube/serenity
synced 2025-07-25 05:27:43 +00:00
Kernel: Don't hog VMObject lock when remapping a region page
We really only need the VMObject lock when accessing the physical pages array, so once we have a strong pointer to the physical page we want to remap, we can give up the VMObject lock. This fixes a deadlock I encountered while building DOOM on SMP.
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parent
10399a258f
commit
b560442fe1
2 changed files with 53 additions and 42 deletions
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@ -202,10 +202,9 @@ ErrorOr<void> Region::set_should_cow(size_t page_index, bool cow)
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return {};
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}
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bool Region::map_individual_page_impl(size_t page_index)
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bool Region::map_individual_page_impl(size_t page_index, RefPtr<PhysicalPage> page)
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{
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VERIFY(m_page_directory->get_lock().is_locked_by_current_processor());
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VERIFY(s_mm_lock.is_locked_by_current_processor());
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auto page_vaddr = vaddr_from_page_index(page_index);
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@ -214,43 +213,53 @@ bool Region::map_individual_page_impl(size_t page_index)
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PANIC("About to map mmap'ed page at a kernel address");
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}
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SpinlockLocker lock(s_mm_lock);
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auto* pte = MM.ensure_pte(*m_page_directory, page_vaddr);
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if (!pte)
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return false;
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auto* page = physical_page(page_index);
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if (!page || (!is_readable() && !is_writable())) {
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pte->clear();
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} else {
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pte->set_cache_disabled(!m_cacheable);
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pte->set_physical_page_base(page->paddr().get());
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pte->set_present(true);
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if (page->is_shared_zero_page() || page->is_lazy_committed_page() || should_cow(page_index))
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pte->set_writable(false);
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else
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pte->set_writable(is_writable());
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if (Processor::current().has_nx())
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pte->set_execute_disabled(!is_executable());
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if (Processor::current().has_pat())
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pte->set_pat(is_write_combine());
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pte->set_user_allowed(user_allowed);
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return true;
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}
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pte->set_cache_disabled(!m_cacheable);
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pte->set_physical_page_base(page->paddr().get());
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pte->set_present(true);
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if (page->is_shared_zero_page() || page->is_lazy_committed_page() || should_cow(page_index))
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pte->set_writable(false);
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else
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pte->set_writable(is_writable());
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if (Processor::current().has_nx())
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pte->set_execute_disabled(!is_executable());
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if (Processor::current().has_pat())
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pte->set_pat(is_write_combine());
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pte->set_user_allowed(user_allowed);
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return true;
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}
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bool Region::remap_vmobject_page(size_t page_index, bool with_flush)
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bool Region::map_individual_page_impl(size_t page_index)
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{
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RefPtr<PhysicalPage> page;
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{
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SpinlockLocker vmobject_locker(vmobject().m_lock);
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page = physical_page(page_index);
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}
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return map_individual_page_impl(page_index, page);
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}
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bool Region::remap_vmobject_page(size_t page_index, NonnullRefPtr<PhysicalPage> physical_page)
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{
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SpinlockLocker page_lock(m_page_directory->get_lock());
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SpinlockLocker mm_lock(s_mm_lock);
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SpinlockLocker lock(m_vmobject->m_lock);
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// NOTE: `page_index` is a VMObject page index, so first we convert it to a Region page index.
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if (!translate_vmobject_page(page_index))
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return false;
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VERIFY(physical_page(page_index));
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bool success = map_individual_page_impl(page_index);
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if (with_flush)
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MemoryManager::flush_tlb(m_page_directory, vaddr_from_page_index(page_index));
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bool success = map_individual_page_impl(page_index, physical_page);
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MemoryManager::flush_tlb(m_page_directory, vaddr_from_page_index(page_index));
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return success;
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}
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@ -286,7 +295,6 @@ void Region::set_page_directory(PageDirectory& page_directory)
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ErrorOr<void> Region::map(PageDirectory& page_directory, ShouldFlushTLB should_flush_tlb)
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{
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SpinlockLocker page_lock(page_directory.get_lock());
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SpinlockLocker lock(s_mm_lock);
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// FIXME: Find a better place for this sanity check(?)
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if (is_user() && !is_shared()) {
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@ -364,7 +372,7 @@ PageFaultResponse Region::handle_fault(PageFault const& fault)
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auto page_index_in_vmobject = translate_to_vmobject_page(page_index_in_region);
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VERIFY(m_vmobject->is_anonymous());
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page_slot = static_cast<AnonymousVMObject&>(*m_vmobject).allocate_committed_page({});
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if (!remap_vmobject_page(page_index_in_vmobject))
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if (!remap_vmobject_page(page_index_in_vmobject, *page_slot))
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return PageFaultResponse::OutOfMemory;
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return PageFaultResponse::Continue;
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}
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@ -403,7 +411,7 @@ PageFaultResponse Region::handle_zero_fault(size_t page_index_in_region)
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if (!page_slot.is_null() && !page_slot->is_shared_zero_page() && !page_slot->is_lazy_committed_page()) {
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dbgln_if(PAGE_FAULT_DEBUG, "MM: zero_page() but page already present. Fine with me!");
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if (!remap_vmobject_page(page_index_in_vmobject))
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if (!remap_vmobject_page(page_index_in_vmobject, *page_slot))
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return PageFaultResponse::OutOfMemory;
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return PageFaultResponse::Continue;
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}
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@ -426,7 +434,7 @@ PageFaultResponse Region::handle_zero_fault(size_t page_index_in_region)
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dbgln_if(PAGE_FAULT_DEBUG, " >> ALLOCATED {}", page_slot->paddr());
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}
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if (!remap_vmobject_page(page_index_in_vmobject)) {
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if (!remap_vmobject_page(page_index_in_vmobject, *page_slot)) {
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dmesgln("MM: handle_zero_fault was unable to allocate a page table to map {}", page_slot);
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return PageFaultResponse::OutOfMemory;
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}
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@ -445,7 +453,7 @@ PageFaultResponse Region::handle_cow_fault(size_t page_index_in_region)
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auto page_index_in_vmobject = translate_to_vmobject_page(page_index_in_region);
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auto response = reinterpret_cast<AnonymousVMObject&>(vmobject()).handle_cow_fault(page_index_in_vmobject, vaddr().offset(page_index_in_region * PAGE_SIZE));
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if (!remap_vmobject_page(page_index_in_vmobject))
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if (!remap_vmobject_page(page_index_in_vmobject, *vmobject().physical_pages()[page_index_in_vmobject]))
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return PageFaultResponse::OutOfMemory;
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return response;
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}
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@ -467,7 +475,7 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region)
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SpinlockLocker locker(inode_vmobject.m_lock);
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if (!vmobject_physical_page_slot.is_null()) {
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dbgln_if(PAGE_FAULT_DEBUG, "handle_inode_fault: Page faulted in by someone else before reading, remapping.");
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if (!remap_vmobject_page(page_index_in_vmobject))
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if (!remap_vmobject_page(page_index_in_vmobject, *vmobject_physical_page_slot))
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return PageFaultResponse::OutOfMemory;
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return PageFaultResponse::Continue;
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}
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@ -511,21 +519,23 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region)
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MM.unquickmap_page();
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}
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// NOTE: The VMObject lock is required when manipulating the VMObject's physical page slot.
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SpinlockLocker locker(inode_vmobject.m_lock);
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{
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// NOTE: The VMObject lock is required when manipulating the VMObject's physical page slot.
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SpinlockLocker locker(inode_vmobject.m_lock);
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if (!vmobject_physical_page_slot.is_null()) {
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// Someone else faulted in this page while we were reading from the inode.
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// No harm done (other than some duplicate work), remap the page here and return.
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dbgln_if(PAGE_FAULT_DEBUG, "handle_inode_fault: Page faulted in by someone else, remapping.");
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if (!remap_vmobject_page(page_index_in_vmobject))
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return PageFaultResponse::OutOfMemory;
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return PageFaultResponse::Continue;
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if (!vmobject_physical_page_slot.is_null()) {
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// Someone else faulted in this page while we were reading from the inode.
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// No harm done (other than some duplicate work), remap the page here and return.
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dbgln_if(PAGE_FAULT_DEBUG, "handle_inode_fault: Page faulted in by someone else, remapping.");
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if (!remap_vmobject_page(page_index_in_vmobject, *vmobject_physical_page_slot))
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return PageFaultResponse::OutOfMemory;
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return PageFaultResponse::Continue;
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}
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vmobject_physical_page_slot = new_physical_page;
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}
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vmobject_physical_page_slot = move(new_physical_page);
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if (!remap_vmobject_page(page_index_in_vmobject))
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if (!remap_vmobject_page(page_index_in_vmobject, *vmobject_physical_page_slot))
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return PageFaultResponse::OutOfMemory;
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return PageFaultResponse::Continue;
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