On 12/08, Eric W. Biederman wrote: > > Oleg Nesterov <[EMAIL PROTECTED]> writes: > > > p->exit_state != 0 doesn't mean this process is dead, it may have > > sub-threads. > > > > However, the new "p->exit_state && thread_group_empty(p)" check is not > > correct > > either, this is just the temporary hack. Perhaps we can just remove this > > check, > > but I don't understand orphaned process groups magic. At all. However, I > > think > > exit_notify() is obviously and completely wrong wrt this helper. > > The problem that orphaned processes groups address is what happens if > an entire process group is stopped, and there is not a process that > can wake them up. > > The rule for an unprivileged process sending a signal to a process > group is that it must be in the same session as the process group. > > The rule for sending a signal to a process group is that the signal sender > must be in the same session. > > So we are testing for a process group that does not have a living > member with a parent outside of the process that can send the process > group a signal.
Ah, thanks a lot Eric, I am _starting_ to understand this. > Oleg what do you see wrong with checking p->exit_state && > thread_group_empty(p)? Since non-leader threads all self reap > that seems to be a valid test for an dead thread group. There is a window when exit_notify() drops tasklist and before release_task(). Suppose the last (non-leader) thread exits. This means that entire group exits, but thread_group_empty() is not true. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
