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Re: [PATCH] malloc: add locking to thread cache
- From: Florian Weimer <fweimer at redhat dot com>
- To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>, Joern Engel <joern at purestorage dot com>, "GNU C. Library" <libc-alpha at sourceware dot org>
- Cc: Siddhesh Poyarekar <siddhesh dot poyarekar at gmail dot com>, nd at arm dot com
- Date: Tue, 26 Jan 2016 14:14:49 +0100
- Subject: Re: [PATCH] malloc: add locking to thread cache
- Authentication-results: sourceware.org; auth=none
- References: <1453767942-19369-1-git-send-email-joern at purestorage dot com> <1453767942-19369-52-git-send-email-joern at purestorage dot com> <56A76A49 dot 8010804 at arm dot com>
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. Fixing this in malloc may seem attractive, but I doubt it
can be made completely reliable by concentrating changes there.
Florian