From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: thread local storage
Date: Mon, 16 Jul 2012 16:09:51 -0400 [thread overview]
Message-ID: <20120716200951.GO544@brightrain.aerifal.cx> (raw)
In-Reply-To: <50046412.4060609@purdue.edu>
On Mon, Jul 16, 2012 at 02:57:22PM -0400, Gregor Richards wrote:
> On 07/16/2012 03:02 PM, John Spencer wrote:
> >2 out of 14 sabotage followers wanted to use a musl-based system
> >as a platform for luajit (and then were never seen again).
> >so i looked into adding it...
> >
> >luajit builds without problems on musl, but then crashes due to a
> >lack of TLS.
> >
> >is it planned to add this feature ? iirc it wasn't mentioned on
> >the latest roadmap...
> >
> >
> >
> With a quick perusal of the LuaJIT source, this is the only instance
> of TLS I see:
>
> #if LJ_UNWIND_EXT
> #if LJ_TARGET_OSX || defined(__OpenBSD__)
> /* Sorry, no thread safety for OSX. Complain to Apple, not me. */
> static _Unwind_Exception static_uex;
> #else
> static __thread _Unwind_Exception static_uex;
> #endif
>
> Convince it to use the same exception as OS X and OpenBSD and you
> should be in business.
This is broken and non-thread-safe. Not a good idea. Instead try:
#define static_uex (*(_Unwind_Exception *)pthread_getspecific(static_uex_key))
where static_uex_key is a pthread_key_t initialized earlier with:
pthread_key_create(&static_uex_key, 0);
And where the thread-specific value of the key is set in thread
startup as:
_Unwind_Exception static_uex_local;
pthread_setspecific(static_uex_key, &static_uex_local);
The simplicity and generality of this solution is why __thread was
just a stupid idea to begin with...
Rich
next prev parent reply other threads:[~2012-07-16 20:09 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-16 19:02 John Spencer
2012-07-16 18:57 ` Gregor Richards
2012-07-16 20:09 ` Rich Felker [this message]
2012-07-16 21:30 ` John Spencer
2012-07-16 22:18 ` Rich Felker
2012-07-16 19:58 ` Justin Cormack
2012-07-16 20:03 ` Rich Felker
2012-07-16 22:06 ` John Spencer
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