Since r218070 reenabled the call to vm_map_simplify_entry() from
vm_map_insert(), the kmem_back() assumption about newly inserted entry might be broken due to interference of two factors. In the low memory condition, when vm_page_alloc() returns NULL, supplied map is unlocked. If another thread performs kmem_malloc() meantime, and its map entry is placed right next to our thread map entry in the map, both entries wire count is still 0 and entries are coalesced due to vm_map_simplify_entry(). Mark new entry with MAP_ENTRY_IN_TRANSITION to prevent coalesce. Fix some style issues, tighten the assertions to account for MAP_ENTRY_IN_TRANSITION state. Reported and tested by: pho Reviewed by: alc
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parent
c43728a230
commit
56bdf2dbc2
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=218701
@ -353,12 +353,24 @@ kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
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vm_map_entry_t entry;
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vm_page_t m;
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int pflags;
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boolean_t found;
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KASSERT(vm_map_locked(map), ("kmem_back: map %p is not locked", map));
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offset = addr - VM_MIN_KERNEL_ADDRESS;
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vm_object_reference(kmem_object);
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vm_map_insert(map, kmem_object, offset, addr, addr + size,
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VM_PROT_ALL, VM_PROT_ALL, 0);
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VM_PROT_ALL, VM_PROT_ALL, 0);
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/*
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* Assert: vm_map_insert() will never be able to extend the
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* previous entry so vm_map_lookup_entry() will find a new
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* entry exactly corresponding to this address range and it
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* will have wired_count == 0.
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*/
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found = vm_map_lookup_entry(map, addr, &entry);
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KASSERT(found && entry->start == addr && entry->end == addr + size &&
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entry->wired_count == 0 && (entry->eflags & MAP_ENTRY_IN_TRANSITION)
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== 0, ("kmem_back: entry not found or misaligned"));
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if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
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pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
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@ -381,9 +393,15 @@ kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
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if (m == NULL) {
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if ((flags & M_NOWAIT) == 0) {
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VM_OBJECT_UNLOCK(kmem_object);
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entry->eflags |= MAP_ENTRY_IN_TRANSITION;
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vm_map_unlock(map);
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VM_WAIT;
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vm_map_lock(map);
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KASSERT(
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(entry->eflags & (MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_NEEDS_WAKEUP)) ==
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MAP_ENTRY_IN_TRANSITION,
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("kmem_back: volatile entry"));
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entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
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VM_OBJECT_LOCK(kmem_object);
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goto retry;
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}
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@ -413,15 +431,11 @@ kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
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VM_OBJECT_UNLOCK(kmem_object);
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/*
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* Mark map entry as non-pageable. Assert: vm_map_insert() will never
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* be able to extend the previous entry so there will be a new entry
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* exactly corresponding to this address range and it will have
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* wired_count == 0.
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* Mark map entry as non-pageable. Repeat the assert.
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*/
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if (!vm_map_lookup_entry(map, addr, &entry) ||
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entry->start != addr || entry->end != addr + size ||
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entry->wired_count != 0)
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panic("kmem_malloc: entry not found or misaligned");
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KASSERT(entry->start == addr && entry->end == addr + size &&
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entry->wired_count == 0,
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("kmem_back: entry not found or misaligned after allocation"));
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entry->wired_count = 1;
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/*
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