On 03/20/11 13:08, Thomas Gleixner wrote:

On Sun, 20 Mar 2011, David Ahern wrote:

quoted

+
+	if (sample_type & PERF_SAMPLE_REALTIME)
+		data->realtime = ktime_to_ns(ktime_get_real());

That's going to live lock on any sample which happens to hit in a
xtime_lock write locked section. I knew why I suggested adding
tracepoints to the timekeeping code :)

Hmmm.... Can you give an example of when perf samples could be generated
with xtime write locked? What are the rules for when ktime_get_real can
be invoked?

David

Thanks,

	tglx