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

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:

quoted

+++ 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