On 2020-11-02 18:01:33 [+0100], Oleg Nesterov wrote:
> So it seems I should send V2 which uses raw_spin_(un)lock_irq().
>
> Or even _irqsave() like ptrace_freeze_traced() does? Although this looks
> confusing, exactly because ptrace_freeze_traced() calls task_is_traced()
> which does raw_spin_lock_irq().
Urgh. Judging from
release_task()
-> write_lock_irq(&tasklist_lock);
-> ptrace_release_task();
-> ptrace_unlink();
-> __ptrace_unlink();
-> task_is_traced().
it will break on !RT so irqsave is indeed needed. And yes, using
task_is_traced() and then acquired the PI lock again looks like too
much.
Either complain or send a patch, I will look tomorrow.
> Oleg.
Sebastian
