Messages in this thread | | | From | Wander Lairson Costa <> | Date | Mon, 6 Feb 2023 15:34:04 -0300 | Subject | Re: [PATCH v4] kernel/fork: beware of __put_task_struct calling context |
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On Mon, Feb 6, 2023 at 12:27 PM Oleg Nesterov <oleg@redhat.com> wrote: > > On 02/06, Sebastian Andrzej Siewior wrote: > > > > On 2023-02-06 10:04:47 [-0300], Wander Lairson Costa wrote: > > > > > @@ -857,6 +857,29 @@ void __put_task_struct(struct task_struct *tsk) > > … > > > +void __put_task_struct(struct task_struct *tsk) > > > +{ > > > + if (IS_ENABLED(CONFIG_PREEMPT_RT) && (!preemptible() || !in_task())) > > > > Is it safe to use the rcu member in any case? > > I thinks it is safe but deserves a comment. I guess Wander misunderstood > me when I asked him to do this... >
Oops, sorry. Next version, I will include this description.
> __put_task_struct() is called when refcount_dec_and_test(&t->usage) succeeds. > > This means that it can't "conflict" with put_task_struct_rcu_user() which > abuses ->rcu the same way; rcu_users has a reference so task->usage can't > be zero after rcu_users 1 -> 0 transition. > > > If so why not use it > > unconditionally? > > performance ? > > > And... I still don't like the name of delayed_put_task_struct_rcu() to me > ___put_task_struct_rcu() looks a bit less confusing, note that we already > have delayed_put_task_struct(). But this is minor. >
Ok, I will change it.
> Oleg. >
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