From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753228AbcD1RJW (ORCPT <rfc822;w@1wt.eu>);
	Thu, 28 Apr 2016 13:09:22 -0400
Received: from merlin.infradead.org ([205.233.59.134]:47223 "EHLO
	merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752286AbcD1RJV (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 28 Apr 2016 13:09:21 -0400
Date: Thu, 28 Apr 2016 19:09:02 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
Subject: Re: [PATCH v2 5/7] perf: Introduce address range filtering
Message-ID: <20160428170902.GS3408@twins.programming.kicks-ass.net>
References: <1461771888-10409-1-git-send-email-alexander.shishkin@linux.intel.com>
 <1461771888-10409-6-git-send-email-alexander.shishkin@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1461771888-10409-6-git-send-email-alexander.shishkin@linux.intel.com>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Apr 27, 2016 at 06:44:46PM +0300, Alexander Shishkin wrote:
> +/*
> + * In order to contain the amount of racy and tricky in the address filter
> + * configuration management, it is a two part process:
> + *
> + * (p1) when userspace mappings change as a result of (1) or (2) or (3) below,
> + *      we update the addresses of corresponding vmas in
> + *	event::addr_filters_offs array and bump the event::addr_filters_gen;
> + * (p2) when an event is scheduled in (pmu::add), it calls
> + *      perf_event_addr_filters_sync() which calls pmu::addr_filters_sync()
> + *      if the generation has changed since the previous call.
> + *
> + * If (p1) happens while the event is active, we restart it to force (p2).

Tiny nit; restart only does ::stop(),::start(), which doesn't go through
::add().

> + *
> + * (1) perf_addr_filters_apply(): adjusting filters' offsets based on
> + *     pre-existing mappings, called once when new filters arrive via SET_FILTER
> + *     ioctl;
> + * (2) perf_addr_filters_adjust(): adjusting filters' offsets based on newly
> + *     registered mapping, called for every new mmap(), with mm::mmap_sem down
> + *     for reading;
> + * (3) perf_event_addr_filters_exec(): clearing filters' offsets in the process
> + *     of exec.
> + */

> +static unsigned long perf_addr_filter_apply(struct perf_addr_filter *filter,
> +					    struct mm_struct *mm)
> +{
> +	struct vm_area_struct *vma;
> +
> +	for (vma = mm->mmap; vma->vm_next; vma = vma->vm_next) {

Doesn't this miss the very last vma? That is, I was expecting:

	for (vma = mm->mmap; vma; 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_addr_filter_match(filter, file, off, vma_size))
> +			continue;
> +
> +		return vma->vm_start;
> +	}
> +
> +	return 0;
> +}