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Date: Fri, 27 Jan 2017 10:38:01 -0700 From: Mathieu Poirier <mathieu.poirier@...aro.org> To: Alexander Shishkin <alexander.shishkin@...ux.intel.com> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>, Ingo Molnar <mingo@...hat.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Vince Weaver <vince@...ter.net>, Stephane Eranian <eranian@...gle.com>, Arnaldo Carvalho de Melo <acme@...radead.org>, Will Deacon <will.deacon@....com>, Mark Rutland <mark.rutland@....com> Subject: Re: [PATCH 3/3] perf: Allow kernel filters on cpu events On 27 January 2017 at 05:31, Alexander Shishkin <alexander.shishkin@...ux.intel.com> wrote: > Mathieu Poirier <mathieu.poirier@...aro.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. Yes, I see it now. Do you have bigger plans for ->nr_file_filters? If the purpose is only to indicate the presence of user space files then it should be a 'bool' type (and probably changed to ->file_filters). Thanks, Mathieu > > Regards, > -- > Alex
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