On Tue, 4 Jul 2023, Alexander Gordeev wrote: > On Sat, Jul 01, 2023 at 09:32:38PM -0700, Hugh Dickins wrote: > > On Thu, 29 Jun 2023, Hugh Dickins wrote: > > Hi Hugh, > > ... > > No, not quite the same rules as before: I came to realize that using > > list_add_tail() for the HH pages would be liable to put a page on the > > list which forever blocked reuse of PP list_add_tail() pages after it > > (could be solved by a list_move() somewhere, but we have agreed to > > prefer simplicity). > > Just to make things more clear for me: do I understand correctly that this > was an attempt to add HH fragments to pgtable_list from pte_free_defer()? Yes, from page_table_free() called from pte_free_defer(): I had claimed they could be put on the list (or not) without needing to consider their HH-ness, apart from wanting to list_add_tail() rather than list_add() them. But then realized that this category of list_add_tail() pages would block access to the others. But I think I was mistaken then to say "could be solved by a list_move() somewhere"; because "somewhere" would have had to be __tlb_remove_table() when it removes PP-bits, which would bring us back to the issues of getting a spinlock from an mm which might already be freed. Hugh
