Re: [PATCH 08/10] ptrace: participate in group stop from ptrace_stop() iff the task is trapping for group stop

[Roland McGrath]

> A visible behavior change is increased likelihood of delayed group
> stop completion if the thread group contains one or more ptraced
> tasks.

I object to that difference in behavior.  As I've said before, I don't
think there should be any option to circumvent a group stop via ptrace.
If you think otherwise, you have a hard road to convince me of it.  

It was always the intent that traced tasks should participate in the
group stop bookkeeping.  I suspect the better line of fixes will be just
to tie up the loose ends of the ptrace interactions so that all ptrace
stops do the correct group_stop_count bookkeeping and notifications.  If
there is a group stop in progress but not yet complete, then PTRACE_CONT
on a thread in the group should probably just move it from TASK_TRACED
to TASK_STOPPED without resuming it at all.  

Once a group stop is complete, then probably the ideal is that
PTRACE_CONT would not resume a thread until a real SIGCONT cleared the
job control stop condition.  But it's likely that existing ptrace users
have expectations contrary to that, so we'll have to see.


Thanks,
Roland
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/