On 05/16, Eric W. Biederman wrote:
>
> A kernel thread can block SIGKILL and that is supported.
>
> For a thread that is part of a process you can't block SIGKILL when the
> task is part of a user mode process.

Or SIGSTOP. Another thread can call do_signal_stop()->signal_wake_up/etc.

> There is this bit in complete_signal when SIGKILL is delivered to any
> thread in the process.
>
>                       t = p;
>                       do {
>                               task_clear_jobctl_pending(t, 
> JOBCTL_PENDING_MASK);
>                               sigaddset(&t->pending.signal, SIGKILL);
>                               signal_wake_up(t, 1);
>                       } while_each_thread(p, t);

That is why the latest version adds try_set_pending_sigkill(). No, no,
it is not that I think this is a good idea.

> For clarity that sigaddset(&t->pending.signal, SIGKILL);  Really isn't
> setting SIGKILL pending,

Hmm. it does? Nevermind.

> The important part of that code is that SIGNAL_GROUP_EXIT gets set.
> That indicates the entire process is being torn down.

Yes. and the same is true for io-thread even if it calls get_signal()
and dequeues SIGKILL and clears TIF_SIGPENDING.

> but in that case the vhost logic needs to act like a process, just
> like io_uring does.

confused... create_io_thread() creates a sub-thread too?

Although I never understood this logic. I can't even understand the usage
of lower_32_bits() in create_io_thread().

Oleg.

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