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    SubjectRe: [PATCH v9] kernel/fork: beware of __put_task_struct calling context
    On 06/01, Wander Lairson Costa wrote:
    >
    > On Thu, Jun 1, 2023 at 3:14 PM Oleg Nesterov <oleg@redhat.com> wrote:
    > >
    > > > but only in the RT kernel
    > >
    > > this again suggests that your testing was wrong or I am totally confused (quite
    > > possible, I know nothing about RT). I did the testing without CONFIG_PREEMPT_RT.
    > >
    >
    > Hrm, could you please share your .config?

    Sure. I do not want to spam the list, I'll send you a private email.

    Can you share your kernel module code?

    Did you verify that debug_locks != 0 as I asked in my previous email ?

    > > > But running the reproducer for put_task_struct(), works fine.
    > >
    > > which reproducer ?
    > >
    >
    > Only now I noticed I didn't add the reproducer to the commit message:
    >
    > while true; do
    > stress-ng --sched deadline --sched-period 1000000000
    > --sched-runtime 800000000 --sched-deadline 1000000000 --mmapfork 23 -t
    > 20
    > done

    Cough ;) I think we need a more simple one to enssure that
    refcount_sub_and_test(nr, &t->usage) returns true under raw_spin_lock()
    and then __put_task_struct() actually takes spin_lock().

    Oleg.

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