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

Peter Zijlstra
2015-05-12T09:39:20Z

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?