Messages in this thread | | | From | Alexander Shishkin <> | Subject | Re: [PATCH 1/3] perf, pt, coresight: Clean up address filter structure | Date | Fri, 27 Jan 2017 14:12:14 +0200 |
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Mathieu Poirier <mathieu.poirier@linaro.org> writes:
> Hi Alex,
Hi Mathieu,
> This changes the behavior we used to have. Now a range filter with a size of 0 > will be treated as start filter rather than an error. See below on a possible > way of fixing this.
Not really. Currently we have 2 drivers using this and both reject the type=range&&size==0 filters with either -EOPNOTSUPP or -EINVAL. With this change, PT will still reject it as it doesn't support single address triggers, but Coresight will treat it as if it was a single address filter. Which makes sense, because that's what a range of size zero is. Note, that a range that covers one instruction has to be at least size==1 (and I'm guessing size==4 for Coresight, but I may be wrong).
So yes, this does change the existing behavior, but in doing so it removes the ambiguity of zero sized ranges.
> if (filter->action == PERF_ADDR_FILTER_ACTION_RANGE)
But "range" is not an action, it's a type of a filter. It determines the condition that triggers an action. An action, however, is what we do when the condition comes true.
Regards, -- Alex
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