linux-kernel - Re: [PATCH 1/1] perf,tools: add time out to force stop endless mmap processing

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Date:	Thu, 11 Jun 2015 09:21:10 -0600
From:	David Ahern <dsahern@...il.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>, kan.liang@...el.com
CC:	linux-kernel@...r.kernel.org, ying.huang@...el.com,
	andi@...stfloor.org
Subject: Re: [PATCH 1/1] perf,tools: add time out to force stop endless mmap
 processing

On 6/11/15 8:06 AM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jun 10, 2015 at 03:46:04AM -0400, kan.liang@...el.com escreveu:
>> perf top reads all threads' /proc/xxx/maps. If there is any threads
>> which generating a keeping growing huge /proc/xxx/maps, perf will do
>> infinite loop in perf_event__synthesize_mmap_events.
>> This patch fixes this issue by adding a time out to force stop this kind
>> of endless mmap processing.
>>
>> Reported-by: Huang, Ying <ying.huang@...el.com>
>> Signed-off-by: Kan Liang <kan.liang@...el.com>
>
> So we will silently stop processing those events?
>
> We will make progress, no doubt, but I think the user needs to be warned
> about this situation, so that later on when/if samples for those maps
> appear and don't get resolved at least we will know that this is the
> reason.

Can you elaborate on an example? I don't see how this can happen reading 
a maps file. And it does not read maps for all threads only thread group 
leaders.

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