Re: [PATCH 5/6] nohz: support PR_DATAPLANE_STRICT mode

Paul E. McKenney
2015-05-12T13:20:13Z

On Tue, May 12, 2015 at 11:38:58AM +0200, Peter Zijlstra wrote:
> On Fri, May 08, 2015 at 01:58:46PM -0400, Chris Metcalf wrote:
> > +++ b/kernel/time/tick-sched.c
> > @@ -436,6 +436,20 @@ static void dataplane_quiesce(void)
> > (jiffies - start));
> > dump_stack();
> > }
> > +
> > + /*
> > + * Kill the process if it violates STRICT mode. Note that this
> > + * code also results in killing the task if a kernel bug causes an
> > + * irq to be delivered to this core.
> > + */
> > + if ((task->dataplane_flags & (PR_DATAPLANE_STRICT|PR_DATAPLANE_PRCTL))
> > + == PR_DATAPLANE_STRICT) {
> > + pr_warn("Dataplane STRICT mode violated; process killed.\n");
> > + dump_stack();
> > + task->dataplane_flags &= ~PR_DATAPLANE_QUIESCE;
> > + local_irq_enable();
> > + do_group_exit(SIGKILL);
> > + }
> > }
>
> So while I'm all for hard fails like this, can we not provide a wee bit
> more information in the siginfo ? And maybe use a slightly less fatal
> signal, such that userspace can actually catch it and dump state in
> debug modes?

Agreed, a bit more debug state would be helpful.

Thanx, Paul