utrace_wakeup:
if (likely(task_is_stopped_or_traced(target))) {
if (target->signal->flags & SIGNAL_STOP_STOPPED)
target->state = TASK_STOPPED;
else
wake_up_state(target, __TASK_STOPPED | __TASK_TRACED);
}
Let's forget about ptrace for the moment.
The code above means that utrace can't wake up the tracee if it was
group-stopped. This looks reasonable, but in that case I don't understand
what should we do if ->report_signal() returns UTRACE_SIGNAL_STOP. I mean,
the attached engine can stop the tracee but can't wake it up?
However, utrace_wakeup() is not right. It only checks SIGNAL_STOP_STOPPED,
but doesn't check ->group_stop_count. But, otoh, we need no checks here,
utrace_wakeup() can just do wake_up_state(__TASK_TRACED) and nothing more
(remember, I am ignoring ptrace issues).
but ptrace_resume() is different, it should wake up the tracee, that is
why it does:
if (task_is_stopped(child)) {
spin_lock_irq(&child->sighand->siglock);
child->signal->flags &= ~SIGNAL_STOP_STOPPED;
spin_unlock_irq(&child->sighand->siglock);
}
and this code is wrong again: what if check ->group_stop_count != 0?
In that case SIGNAL_STOP_STOPPED can be set later, when utrace_wakeup()
is called.
(note that we have more problems with utrace_report_jctl() playing
with task->state/signal->flags, should be fixed by the cleanups
discussed in another thread).
What can we do? I don't see any solution.
Oleg.
