Messages in this thread | | | Date | Fri, 24 Aug 2007 14:56:13 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: [PATCH RT 3/3] fix get_monotonic_cycles for latency tracer |
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-- On Fri, 24 Aug 2007, john stultz wrote:
> > > > - /* calculate the delta since the last update_wall_time: */ > > - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > > + } while (cycle_raw != clock->cycle_raw || > > + cycle_last != clock->cycle_last); > > So if I'm understanding this right, not taking a lock isn't an > optimization (as the seq read lock code is almost the same), but a > requirement (as this might be called while xtime_lock is held), > correct?
Exactly. The latency tracer uses this so no locks can be grabbed (seq_locks included).
> > Might want to clarify that a bit in the comment. >
OK, will do and send a updated patch.
I wasn't in the best state writing this patch in the wee hours of the night ;-)
-- Steve
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