From: Jens Gustedt <jens.gustedt@inria.fr>
To: musl@lists.openwall.com
Subject: Re: atomic.h cleanup
Date: Thu, 14 Jan 2016 23:37:48 +0100 [thread overview]
Message-ID: <1452811068.5797.9.camel@inria.fr> (raw)
In-Reply-To: <20160114221257.GS238@brightrain.aerifal.cx>
[-- Attachment #1: Type: text/plain, Size: 2164 bytes --]
Am Donnerstag, den 14.01.2016, 17:12 -0500 schrieb Rich Felker:
> There are already multiple reasons we don't use the compiler's
> atomics, either directly or indirectly via stdatomic.h. They're not
> supported in some old/alternative compilers, they generate highly
> suboptimal code even on modern compilers for some important archs
> (e.g. ARM),
I have seen some pretty good assembler when using the
__atomic... builtins, so I can't completely follow, here.
> and they fail to properly support archs where it's
> necessary to make a runtime choice of which atomic code paths to use
> in order to achieve safe/correct behavior.
ok
> > > > Last time I looked, all usages but one of atomic operations in musl
> > > > are clean. If an atomic operation is used for a data a some point,
> > > > atomic operations are used in all other places. So moving to
> > > > _Atomic(int) would be a option. (Basically this would be `volatile
> > > > int*` => `_Atomic(int)`, IIRC).
> >
> > oops I meant `volatile int*` => `_Atomic(int)*`
> >
> > > pthread_once_t and pthread_spinlock_t are
> > > publicly visibles type (without volatile and
> > > _Atomic)
> > >
> > > i dont think we can fix those without abi
> > > change.
> >
> > This is really a question what ABI means in this case. The width,
> > alignment and representation of the `int` would stay the same, we
> > would just internally (to the library implementation) interpret it as
> > _Atomic(int).
>
> From a C++ perspective ABI certainly includes the type that will
> appear in mangled function names. This is the main motivation for not
> changing types like this. Of course LTO could also break when formal
> types don't match.
Yes, I know. I was thinking of a way to have the externally visible
type remain stable, but internally use _Atomic.
Jens
--
:: INRIA Nancy Grand Est ::: Camus ::::::: ICube/ICPS :::
:: ::::::::::::::: office Strasbourg : +33 368854536 ::
:: :::::::::::::::::::::: gsm France : +33 651400183 ::
:: ::::::::::::::: gsm international : +49 15737185122 ::
:: http://icube-icps.unistra.fr/index.php/Jens_Gustedt ::
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 181 bytes --]
next prev parent reply other threads:[~2016-01-14 22:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-10 12:21 Markus Wichmann
2016-01-10 16:57 ` Rich Felker
2016-01-10 17:35 ` Markus Wichmann
2016-01-10 17:50 ` Alexander Monakov
2016-01-11 16:35 ` Markus Wichmann
2016-01-11 17:12 ` Jens Gustedt
2016-01-11 19:03 ` Szabolcs Nagy
2016-01-11 20:56 ` Jens Gustedt
2016-01-14 22:12 ` Rich Felker
2016-01-14 22:37 ` Jens Gustedt [this message]
2016-01-14 23:32 ` Rich Felker
2016-01-15 0:46 ` Szabolcs Nagy
2016-01-10 17:37 ` Markus Wichmann
2016-01-22 0:09 ` Rich Felker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1452811068.5797.9.camel@inria.fr \
--to=jens.gustedt@inria.fr \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).