[PATCH] malloc: add locking to thread cache

[Yury Gribov]

On 01/26/2016 04:14 PM, Florian Weimer wrote:
> On 01/26/2016 01:44 PM, Szabolcs Nagy wrote:
>> On 26/01/16 00:25, Joern Engel wrote:
>>> With signals we can reenter the thread-cache.  Protect against that with
>>> a lock.  Will almost never happen in practice, it took the company five
>>> years to reproduce a similar race in the existing malloc.  But easy to
>>> trigger with a targeted test.
>>
>> why do you try to make malloc as-safe?
>>
>> isn't it better to fix malloc usage in signal handlers?
>
> We have functionality like dprintf, syslog, backtrace, C++ thread-local
> object access which might be used from signal handlers, but which can
> call malloc.

Right.  One can argue that this is an error and someone should go fix 
the code but in my experience most real-world signal handlers have these 
problems and noone is going to rewrite them any time soon.

> Fixing this in malloc may seem attractive, but I doubt it
> can be made completely reliable by concentrating changes there.
>
> Florian
>
>
>