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Message-ID: <20151213145950.GH23362@port70.net>
Date: Sun, 13 Dec 2015 15:59:50 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: stdatomic implementation
* Jens Gustedt <jens.gustedt@...ia.fr> [2015-12-13 11:01:22 +0100]:
> Its integration into musl should be straight forward and remains my
> primary choice for having it distributed. You can find it at
>
> stdatomic.gforge.inria.fr
>
nice
i recently run into a problem that you may be interested in:
the gcc atomic builtins do not handle atomic pointer types as
expected.
T *p;
__atomic_fetch_add(&p,1);
adds 1 to (char*)p instead of sizeof(T).
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64843
> Under the hood it uses a new lock algorithm based on futex waits for
> the slow path, that has proven to be more efficient than anything else
> that I looked at: musl's internal lock, mtx_t or pthread_mutex_t, or
> spinlocks. You can find a discussion of that at
>
> https://hal.inria.fr/hal-01236734
>
> Before I go (more) public with this, I would very much like to hear
> what you think.
i havent read the paper yet but it is worth noting that
glibc implements weaker pthread semantics than musl, so
on glibc pthread_mutex_lock/unlock is acquire/release.
(which makes pthread_mutex_trylock non-conforming, but
it's closer to the c11 semantics, same for spinlocks).
so it would be interesting to benchmark against glibc
primitives too.
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