malloc: Trim unused arenas on thread exit

[Florian Weimer]

On 11/15/2017 03:00 PM, Siddhesh Poyarekar wrote:
> On Wednesday 15 November 2017 07:06 PM, Florian Weimer wrote:
>> Here's a patch which does just that.  Tested with and without
>> --disable-experimental-malloc.
>>
>> It doesn't have any consolidation/trimming changes.
> 
> LGTM, I trust you'll write a nice git commit log to explain the change :)

I assumed the comment was sufficient:

>>   static void __attribute__ ((section ("__libc_thread_freeres_fn")))
>>   arena_thread_freeres (void)
>>   {
>> +  /* Shut down the thread cache first.  This could deallocate data for
>> +     the thread arena, so do this before we put the arena on the free
>> +     list.  */
>> +  tcache_thread_shutdown ();

If it is not, we need to put more documentation in the code itself.

Thanks,
Florian