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

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On Fri, 24 Aug 2007, john stultz wrote:

quoted

-	/* 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