Messages in this thread | | | From | Alexander Shishkin <> | Subject | Re: [PATCH 3/3] perf: Allow kernel filters on cpu events | Date | Fri, 27 Jan 2017 14:31:22 +0200 |
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Mathieu Poirier <mathieu.poirier@linaro.org> writes:
> On Thu, Jan 26, 2017 at 11:40:57AM +0200, Alexander Shishkin wrote: >> + if (!ifh->nr_file_filters) >> + return; > > Is this mandatory or an optimisation to avoid circling through a list of filters > that don't included user space files?
It's both. It stems from the fact that the remainder of this function relies on ctx::task not being NULL, which is not the case with cpu contexts and now that we've enabled address filters for such contexts, it's a problem. So checking for !task would have done the trick here, but this way we'll also avoid going down this path for task contexts in the absence of file-based filters. In particular, grabbing the mmap semaphore and filters spinlock we can do without.
Regards, -- Alex
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