Just noticed I didn't reply to this message,
On 10/30, Roland McGrath wrote:
>
> > If the tracee was STOPPED/TRACED, then it is equivalent to
> > PTRACE_CONT,SIGKILL.
> > Otherwise it has no effect except it can race with exit() and spoil
> > ->exit_code,
> > and wake_up_process() is not good if course. (I am talking about upstream).
>
> Correct. In job control stop (including one already turned into
> TASK_TRACED by a prior ptrace call), the resumption signal is ignored.
> So the only reliable effect at all is when it's in a proper ptrace stop
> that doesn't otherwise swallow signals (i.e. exactly PTRACE_CONT,SIGKILL
> that ignores liveness/stoppedness errors). In every other case it has
> no effect at best, so fixing that to "no effect at all" is just fine.
>
> > Please tell me what do you think, then I'll do other changes you suggested.
>
> In the old code, PTRACE_KILL can never fail once the initial attachedness
> test has passed. So:
>
> (void) ptrace_resume(child, engine, request, SIGKILL);
> ret = 0; /* Historical compatibility. */
>
> is probably fine.
Yes, but utrace-ptrace does a lot more in ptrace_resume() compared
to upstream. If the tracee is not stopped, then ptrace_resume() can
race with the tracee in many ways. This is mostly harmless, I think,
but still I did
if (task_is_traced(child))
ptrace_resume(PTRACE_CONT, SIGKILL);
ret = 0;
Oleg.
