On Wed, 2008-01-09 at 18:29 -0500, Steven Rostedt wrote: > +cycle_t notrace get_monotonic_cycles(void) > +{ > + cycle_t cycle_now, cycle_delta, cycle_raw, cycle_last; > + > + do { > + /* > + * cycle_raw and cycle_last can change on > + * another CPU and we need the delta calculation > + * of cycle_now and cycle_last happen atomic, as well > + * as the adding to cycle_raw. We don't need to grab > + * any locks, we just keep trying until get all the > + * calculations together in one state. > + * > + * In fact, we __cant__ grab any locks. This > + * function is called from the latency_tracer which can > + * be called anywhere. To grab any locks (including > + * seq_locks) we risk putting ourselves into a deadlock. > + */ > + cycle_raw = clock->cycle_raw; > + cycle_last = clock->cycle_last; > + > + /* read clocksource: */ > + cycle_now = clocksource_read(clock); > + > + /* calculate the delta since the last update_wall_time: */ > + cycle_delta = (cycle_now - cycle_last) & clock->mask; > + > + } while (cycle_raw != clock->cycle_raw || > + cycle_last != clock->cycle_last); > + > + return cycle_raw + cycle_delta; > +}
The last I check this changed caused problems for me with the -rt latency tracer.. I haven't tested this tree , but all things being equal I would imagine the exists here also.. Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/