linux-kernel - Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering

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Date:	Fri, 11 Dec 2015 16:12:29 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	vince@...ter.net, eranian@...gle.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering

On Fri, Dec 11, 2015 at 03:36:36PM +0200, Alexander Shishkin wrote:
> +/*
> + * Scan through mm's vmas and see if one of them matches the
> + * @filter; if so, adjust filter's address range.
> + * Called with mm::mmap_sem down for reading.
> + */
> +static int perf_itrace_filter_apply(struct perf_event *event,
> +				    struct perf_itrace_filter *filter,
> +				    struct mm_struct *mm)
> +{
> +	struct vm_area_struct *vma;

	lockdep_assert_held(&mm->mmap_sem);

If you want to be pedantic we could add:

	lockdep_assert_held_shared()
	lockdep_assert_held_exclusive()

to assert we hold it in any particular state.

> +
> +	for (vma = mm->mmap; vma->vm_next; vma = vma->vm_next) {
> +		struct file *file = vma->vm_file;
> +		unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
> +		unsigned long vma_size = vma->vm_end - vma->vm_start;
> +
> +		if (!file)
> +			continue;
> +
> +		if (!perf_itrace_filter_match(filter, file, off,
> +					      vma_size))
> +			continue;
> +
> +		filter->start = vma->vm_start + filter->offset;
> +		filter->end = vma->vm_start + filter->offset +
> +			filter->size;
> +
> +		return 1;
> +	}
> +
> +	return 0;
> +}
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