On Sat, Nov 30, 2019 at 10:03 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> I'll try to figure the code out, but my initial reaction was "yeah,
> not in my VM".
Why is it ok to sometimes do
WRITE_ONCE(mni->invalidate_seq, cur_seq);
(to pair with the unlocked READ_ONCE), and sometimes then do
mni->invalidate_seq = mmn_mm->invalidate_seq;
My initial guess was that latter is only done at initialization time,
but at least in one case it's done *after* the mni has been added to
the mmn_mm (oh, how I despise those names - I can only repeat: WTF?).
See __mmu_interval_notifier_insert() in the
mmn_mm->active_invalidate_ranges case.
I'm guessing that it doesn't matter, because when inserting the
notifier the sequence number is presumably not used until after the
insertion (and any use though mmn_mm is protected by the
mmn_mm->lock), but it still looks odd to me.
Linus
