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Date: Sat, 25 Jul 2015 14:12:46 +0200
From: Jens Gustedt <>
Subject: Re: implement stdatomic.h library interface


Am Samstag, den 25.07.2015, 11:17 +0200 schrieb Joakim Sindholt:
> On Sat, 2015-07-25 at 08:33 +0200, Jens Gustedt wrote:
> > clang relies on the C library (it seems on bsd) or a gcc installation
> > as a fallback.
> I'm not sure what you mean by this. Can you clarify? Compiler-rt has all
> of clang's own fallback symbols and it looks like they're incompatible
> with libatomic.
> As far as I can tell they just use regular spinlocks on linux without
> any libc dependency what-so-ever and on FreeBSD it goes straight to
> _umtx_op which looks like their version of futex.

so I must have read some obsolete documentation somewhere

In any case a lock with kernel support seems to be preferable. I have
a test application that wildly allocates and deallocates list elements
and inserts them atomically. When there is a 16 byte atomic all is
done with that, if not the lockfull replacement is used. For the
lockfull version I seem to get 3 times more work done when using
LOCK/UNLOCK over just using a spinlock.


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