On Fri, Aug 21, 2020 at 9:37 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > > again, don't really understand... > > On 08/21, Suren Baghdasaryan wrote: > > > > Actually, reviewing again and considering where list_add_tail_rcu is > > happening, maybe the race with clone(CLONE_VM) does not introduce > > false negatives. > > I think it does... Whatever we check, mm_users or MMF_PROC_SHARED, > the task can do clone(CLONE_VM) right after the check. Ah, yes of course. I missed this same just like in the original patch. > > > However a false negative I think will happen when a > > task shares mm with another task and also has an additional thread. > > Shared mm will increment mm_users without adding to signal->live > > Yes, > > > and > > the additional thread will advance signal->live without adding to > > mm_users. > > No, please note that CLONE_THREAD requires CLONE_VM. My fault. Forgot that CLONE_VM means "share VM" and not "dup VM". Need some coffee. Thanks Oleg! > > Oleg. >
