On 12/09, Eric W. Biederman wrote:
>
> Equally messed up is a our status in /proc at that point. Which
> says our sleeping process is a zombie.
Yes, this is annoying.
> I'm thinking we need to do at least some of the thread group leadership
> transfer in do_exit, instead of de_thread. Then p->group_leader->exit_state
> would be sufficient to see if the entire thread group was alive,
> as the group_leader would be whoever was left alive. The original
> group_leader might still need to be kept around for it's pid...
>
> I think that would solve most of the problems you have with a dead
> thread group leader and sending SIG_STOP as well.
Yes I was thinking about that too, but I am not brave enough to even
try to to think to the end ;)
As a minimal change, I tried to add "task_struct *leader_proxy" to
signal_struct, which points to the next live thread, and changed by
exit_notify(). eligible_child() checks it instead of ->exit_signal.
But this is so messy...
And in fact, if we are talking about group stop, it is a group operation,
why do_wait() uses per-thread ->exit_code but not ->group_exit_code ?
But yes, [PATCH 3/3] adds a visible difference, and I don't know if
this difference is good or bad.
$ sleep 1000
[1]+ Stopped sleep 1000
$ strace -p `pidof sleep`
Process 432 attached - interrupt to quit
Now strace "hangs" in do_wait() because ->exit_code was eaten by the
shell. We need SIGCONT.
With the "[PATCH 3/3]" strace proceeds happily.
Oleg.
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