Re: [PATCH RT 3/3] fix get_monotonic_cycles for latency tracer

[Steven Rostedt <rostedt@goodmis.org>]

--
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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