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

[David Ahern <dsahern@gmail.com>]

On 6/11/15 8:06 AM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jun 10, 2015 at 03:46:04AM -0400, kan.liang@intel.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@intel.com>
>> Signed-off-by: Kan Liang <kan.liang@intel.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.